JAVA代理原始碼詳解,手動擼一個屬於自己的代理
一:常用的java代理模式
一般經常做java開發的知道java的代理模式一共有三種,第一種也就是靜態代理,這種用法比較簡單,沒有什麼魔法棒,比較好理解,另外兩種分別是JDK代理和cglib代理,他們分別是對介面代理和對class類本身進行代理,jdk代理要求類必須實現有一個或者多個介面,對介面進行位元組碼增強在記憶體中實現新的class類去反射呼叫使用者target的實現類,這裡需要說明的是不管是cglic代理也好還是jdk代理他們在記憶體中都要佔據方法區資源(jdk8 叫原空間),從而達到代理目的,而cglib代理是對class類本身進行位元組碼增強配合fastclass來實現代理,關於更多的cglib和jdk代理相關的內容大家可以google搜尋一下,網上有很多這裡不做再多的說明。下面我們摒棄jdk,和cglib的複雜原始碼來自己實現一個代理模式,來更深刻的瞭解一下代理究竟是怎麼形成的。
二:JDK代理原始碼分析
②被代理類實現業務介面;
③定義代理類並實現業務介面;
④最後便可通過客戶端進行呼叫。(這裡可以理解成程式的main方法裡的內容)
我們按照這個步驟去實現靜態代理。需求:在向資料庫新增一個使用者時前後列印日誌。
public interface IUserService {
void add(String name);
}
UserServiceImpl.java
public class UserServiceImpl implements IUserService{
@Override
public void add(String name) {
System.out.println("資料庫中插入: "+name+" 的使用者");
}
}
MyInvocationHandler.java
public class MyInvocationHandler implements InvocationHandler {
//被代理物件,Object型別
private Object target;
public MyInvocationHandler(Object target) {
this.target = target;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("準備向資料庫中插入資料");
Object returnvalue = method.invoke(target, args);
System.out.println("插入資料庫成功");
return returnvalue;
}
}
測試類
public static void main(String[] args) {
IUserService target = new UserServiceImpl();
MyInvocationHandler handler = new MyInvocationHandler(target);
IUserService proxyObject = (IUserService) Proxy.newProxyInstance(DynamicProxyTest.class.getClassLoader(),
target.getClass().getInterfaces(), handler);
proxyObject.add("張玉龍");
}
使用上非常簡單、網上demo也很多,不做充分講解,對jdk代理用法的小夥伴如果還不熟悉這塊程式碼,就先了解一下jdk代理的使用方式,然後在回來繼續看下面的原始碼分析
JDK代理原始碼深度分析
Proxy.newProxyInstance( ClassLoaderloader, Class[] interfaces, InvocationHandler h)
產生了代理物件,所以我們進到
newProxyInstance
的實現:
public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
Objects.requireNonNull(h);
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* Look up or generate the designated proxy class.
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
if (sm != null) {
checkNewProxyPermission(Reflection.getCallerClass(), cl);
}
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (!Modifier.isPublic(cl.getModifiers())) {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
cons.setAccessible(true);
return null;
}
});
}
return cons.newInstance(new Object[]{h});
} catch (IllegalAccessException|InstantiationException e) {
throw new InternalError(e.toString(), e);
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString(), t);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString(), e);
}
}
getProxyClass0(loader, intfs)
得到代理類的Class物件,然後通過Class物件得到構造方法,進而建立代理物件。下一步看
getProxyClass0
這個方法。
//此方法也是Proxy類下的方法
private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
// If the proxy class defined by the given loader implementing
// the given interfaces exists, this will simply return the cached copy;
// otherwise, it will create the proxy class via the ProxyClassFactory
//意思是:如果代理類被指定的類載入器loader定義了,並實現了給定的介面interfaces,
//那麼就返回快取的代理類物件,否則使用ProxyClassFactory建立代理類。
return proxyClassCache.get(loader, interfaces);
}
這裡看到proxyClassCache,有Cache便知道是快取的意思,正好呼應了前面Look up or generate the designated proxy class。查詢(在快取中已經有)或生成指定的代理類的class物件這段註釋。
proxyClassCache
是個WeakCache類的物件,呼叫proxyClassCache.get(loader, interfaces); 可以得到快取的代理類或建立代理類(沒有快取的情況)。說明WeakCache中有
get
這個方法。先看下WeakCache類的定義(這裡先只給出變數的定義和建構函式):
//K代表key的型別,P代表引數的型別,V代表value的型別。
// WeakCache<ClassLoader, Class<?>[], Class<?>> proxyClassCache 說明proxyClassCache存的值是Class<?>物件,正是我們需要的代理類物件。
final class WeakCache<K, P, V> {
private final ReferenceQueue<K> refQueue
= new ReferenceQueue<>();
// the key type is Object for supporting null key
private final ConcurrentMap<Object, ConcurrentMap<Object, Supplier<V>>> map
= new ConcurrentHashMap<>();
private final ConcurrentMap<Supplier<V>, Boolean> reverseMap
= new ConcurrentHashMap<>();
private final BiFunction<K, P, ?> subKeyFactory;
private final BiFunction<K, P, V> valueFactory;
public WeakCache(BiFunction<K, P, ?> subKeyFactory,
BiFunction<K, P, V> valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory);
this.valueFactory = Objects.requireNonNull(valueFactory);
}
(key, sub-key) -> value
。其中key是傳進來的Classloader進行包裝後的物件,sub-key是由WeakCache建構函式傳人的
KeyFactory()
生成的。value就是產生代理類的物件,是由WeakCache建構函式傳人的
ProxyClassFactory()
生成的
好,大體上說完WeakCache這個類的作用,我們回到剛才
proxyClassCache.get(loader, interfaces);
這句程式碼。get是WeakCache裡的方法。原始碼如下
//K和P就是WeakCache定義中的泛型,key是類載入器,parameter是介面類陣列
public V get(K key, P parameter) {
//檢查parameter不為空
Objects.requireNonNull(parameter);
//清除無效的快取
expungeStaleEntries();
// cacheKey就是(key, sub-key) -> value裡的一級key,
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
//根據一級key得到 ConcurrentMap<Object, Supplier<V>>物件。如果之前不存在,則新建一個ConcurrentMap<Object, Supplier<V>>和cacheKey(一級key)一起放到map中。
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
// create subKey and retrieve the possible Supplier<V> stored by that
// subKey from valuesMap
//這部分就是呼叫生成sub-key的程式碼,上面我們已經看過怎麼生成的了
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
//通過sub-key得到supplier
Supplier<V> supplier = valuesMap.get(subKey);
//supplier實際上就是這個factory
Factory factory = null;
while (true) {
//如果快取裡有supplier ,那就直接通過get方法,得到代理類物件,返回,就結束了,一會兒分析get方法。
if (supplier != null) {
// supplier might be a Factory or a CacheValue<V> instance
V value = supplier.get();
if (value != null) {
return value;
}
}
// else no supplier in cache
// or a supplier that returned null (could be a cleared CacheValue
// or a Factory that wasn't successful in installing the CacheValue)
// lazily construct a Factory
//下面的所有程式碼目的就是:如果快取中沒有supplier,則建立一個Factory物件,把factory物件在多執行緒的環境下安全的賦給supplier。
//因為是在while(true)中,賦值成功後又回到上面去調get方法,返回才結束。
if (factory == null) {
factory = new Factory(key, parameter, subKey, valuesMap);
}
if (supplier == null) {
supplier = valuesMap.putIfAbsent(subKey, factory);
if (supplier == null) {
// successfully installed Factory
supplier = factory;
}
// else retry with winning supplier
} else {
if (valuesMap.replace(subKey, supplier, factory)) {
// successfully replaced
// cleared CacheEntry / unsuccessful Factory
// with our Factory
supplier = factory;
} else {
// retry with current supplier
supplier = valuesMap.get(subKey);
}
}
}
}
所以接下來我們看Factory類中的get方法。
public synchronized V get() { // serialize access
// re-check
Supplier<V> supplier = valuesMap.get(subKey);
//重新檢查得到的supplier是不是當前物件
if (supplier != this) {
// something changed while we were waiting:
// might be that we were replaced by a CacheValue
// or were removed because of failure ->
// return null to signal WeakCache.get() to retry
// the loop
return null;
}
// else still us (supplier == this)
// create new value
V value = null;
try {
//代理類就是在這個位置呼叫valueFactory生成的
//valueFactory就是我們傳入的 new ProxyClassFactory()
//一會我們分析ProxyClassFactory()的apply方法
value = Objects.requireNonNull(valueFactory.apply(key, parameter));
} finally {
if (value == null) { // remove us on failure
valuesMap.remove(subKey, this);
}
}
// the only path to reach here is with non-null value
assert value != null;
// wrap value with CacheValue (WeakReference)
//把value包裝成弱引用
CacheValue<V> cacheValue = new CacheValue<>(value);
// put into reverseMap
// reverseMap是用來實現快取的有效性
reverseMap.put(cacheValue, Boolean.TRUE);
// try replacing us with CacheValue (this should always succeed)
if (!valuesMap.replace(subKey, this, cacheValue)) {
throw new AssertionError("Should not reach here");
}
// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}
}
撥雲見日,來到ProxyClassFactory的apply方法,代理類就是在這裡生成的。
//這裡的BiFunction<T, U, R>是個函式式介面,可以理解為用T,U兩種型別做引數,得到R型別的返回值
private static final class ProxyClassFactory
implements BiFunction<ClassLoader, Class<?>[], Class<?>>
{
// prefix for all proxy class names
//所有代理類名字的字首
private static final String proxyClassNamePrefix = "$Proxy";
// next number to use for generation of unique proxy class names
//用於生成代理類名字的計數器
private static final AtomicLong nextUniqueNumber = new AtomicLong();
@Override
public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {
Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
//驗證代理介面,可不看
for (Class<?> intf : interfaces) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
Class<?> interfaceClass = null;
try {
interfaceClass = Class.forName(intf.getName(), false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != intf) {
throw new IllegalArgumentException(
intf + " is not visible from class loader");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
//生成的代理類的包名
String proxyPkg = null; // package to define proxy class in
//代理類訪問控制符: public ,final
int accessFlags = Modifier.PUBLIC | Modifier.FINAL;
/*
* Record the package of a non-public proxy interface so that the
* proxy class will be defined in the same package. Verify that
* all non-public proxy interfaces are in the same package.
*/
//驗證所有非公共的介面在同一個包內;公共的就無需處理
//生成包名和類名的邏輯,包名預設是com.sun.proxy,類名預設是$Proxy 加上一個自增的整數值
//如果被代理類是 non-public proxy interface ,則用和被代理類介面一樣的包名
for (Class<?> intf : interfaces) {
int flags = intf.getModifiers();
if (!Modifier.isPublic(flags)) {
accessFlags = Modifier.FINAL;
String name = intf.getName();
int n = name.lastIndexOf('.');
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}
if (proxyPkg == null) {
// if no non-public proxy interfaces, use com.sun.proxy package
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
/*
* Choose a name for the proxy class to generate.
*/
long num = nextUniqueNumber.getAndIncrement();
//代理類的完全限定名,如com.sun.proxy.$Proxy0.calss
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Generate the specified proxy class.
*/
//核心部分,生成代理類的位元組碼
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
//把代理類載入到JVM中,至此動態代理過程基本結束了
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
/*
* A ClassFormatError here means that (barring bugs in the
* proxy class generation code) there was some other
* invalid aspect of the arguments supplied to the proxy
* class creation (such as virtual machine limitations
* exceeded).
*/
throw new IllegalArgumentException(e.toString());
}
}
}
到這裡其實已經分析完了,但是本著深究的態度,決定看看JDK生成的動態代理位元組碼是什麼,於是我們將位元組碼儲存到磁碟上的class檔案中。程式碼如下:
public static void main(String[] args) {
IUserService target = new UserServiceImpl();
MyInvocationHandler handler = new MyInvocationHandler(target);
//第一個引數是指定代理類的類載入器(我們傳入當前測試類的類載入器)
//第二個引數是代理類需要實現的介面(我們傳入被代理類實現的介面,這樣生成的代理類和被代理類就實現了相同的介面)
//第三個引數是invocation handler,用來處理方法的呼叫。這裡傳入我們自己實現的handler
IUserService proxyObject = (IUserService) Proxy.newProxyInstance(DynamicProxyTest.class.getClassLoader(),
target.getClass().getInterfaces(), handler);
proxyObject.add("張玉龍");
String path = "D:/$Proxy0.class";
byte[] classFile = ProxyGenerator.generateProxyClass("$Proxy0", HelloworldImpl.class.getInterfaces());
FileOutputStream out = null;
try {
out = new FileOutputStream(path);
out.write(classFile);
out.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
執行這段程式碼,會在D盤生成一個名為$Proxy0.class的檔案。通過反編譯工具,得到JDK為我們生成的代理類是這樣的:
// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi space
import com.zhb.jdk.proxy.IUserService;
import java.lang.reflect.*;
public final class $Proxy0 extends Proxy
implements IUserService
{
private static Method m1;
private static Method m2;
private static Method m3;
private static Method m0;
//代理類的建構函式,其引數正是是InvocationHandler例項,
//Proxy.newInstance方法就是通過通過這個建構函式來建立代理例項的
public $Proxy0(InvocationHandler invocationhandler)
{
super(invocationhandler);
}
// Object類中的三個方法,equals,toString, hashCode
public final boolean equals(Object obj)
{
try
{
return ((Boolean)super.h.invoke(this, m1, new Object[] {
obj
})).booleanValue();
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
public final String toString()
{
try
{
return (String)super.h.invoke(this, m2, null);
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
//介面代理方法
public final void add(String s)
{
try
{
// invocation handler的 invoke方法在這裡被呼叫
super.h.invoke(this, m3, new Object[] {
s
});
return;
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
public final int hashCode()
{
try
{
// 在這裡呼叫了invoke方法。
return ((Integer)super.h.invoke(this, m0, null)).intValue();
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
// 靜態程式碼塊對變數進行一些初始化工作
static
{
try
{
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] {
Class.forName("java.lang.Object")
});
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m3 = Class.forName("com.zhb.jdk.proxy.IUserService").getMethod("add", new Class[] {
Class.forName("java.lang.String")
});
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
}
catch (NoSuchMethodException nosuchmethodexception)
{
throw new NoSuchMethodError(nosuchmethodexception.getMessage());
}
catch (ClassNotFoundException classnotfoundexception)
{
throw new NoClassDefFoundError(classnotfoundexception.getMessage());
}
}
}
生成了Object類的三個方法:toString,hashCode,equals。還有我們需要被代理的方法。
JDK代理類的cache clear機制
大家都知道、在專案中被代理的class越來越多,所以jdk會搞一個cache的方式來防止相同的代理介面重複生成class,影響效能不說,實現也不是很優雅,那麼現在就會有一個問題了,當classloader已經在記憶體中沒有依賴的時候,被代理的proxy class其實也沒有什麼意義了,這樣就需要清空無用的cache,java Proxy採用了非常巧妙的“弱引用機制”,我們來看下面的程式碼
我們還是繼續看get方法的原始碼
public V get(K key, P parameter) {
Objects.requireNonNull(parameter);
expungeStaleEntries();
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
.......
}
其中原始碼中有一個方法expungeStaleEntries、我們進去這個方法一窺究竟
private void expungeStaleEntries() {
CacheKey<K> cacheKey;
while ((cacheKey = (CacheKey<K>)refQueue.poll()) != null) {
cacheKey.expungeFrom(map, reverseMap);
}
}
在看看expungeFrom方法原始碼幹了些什麼
void expungeFrom(ConcurrentMap<?, ? extends ConcurrentMap<?, ?>> map,
ConcurrentMap<?, Boolean> reverseMap) {
// removing just by key is always safe here because after a CacheKey
// is cleared and enqueue-ed it is only equal to itself
// (see equals method)...
ConcurrentMap<?, ?> valuesMap = map.remove(this);
// remove also from reverseMap if needed
if (valuesMap != null) {
for (Object cacheValue : valuesMap.values()) {
reverseMap.remove(cacheValue);
}
}
}
程式碼很清晰了,清空被代理的物件。現在的關鍵就是refQueue物件是怎麼來的。我們繼續找一下跟refQueue相關的原始碼、在get中還有一段程式碼是這樣的
Object cacheKey = CacheKey.valueOf(key, refQueue);
private static final class CacheKey<K> extends WeakReference<K> {
// a replacement for null keys
private static final Object NULL_KEY = new Object();
static <K> Object valueOf(K key, ReferenceQueue<K> refQueue) {
return key == null
// null key means we can't weakly reference it,
// so we use a NULL_KEY singleton as cache key
? NULL_KEY
// non-null key requires wrapping with a WeakReference
: new CacheKey<>(key, refQueue);
}
private final int hash;
private CacheKey(K key, ReferenceQueue<K> refQueue) {
super(key, refQueue);
this.hash = System.identityHashCode(key); // compare by identity
}
.....
}
這樣看就非常清晰了、原來是CacheKey繼承了WeakReference弱引用機制,當弱引用依賴的key沒有引用的時候,當前失效的物件就會進入ReferenceQueue中來實現清空cache的功能、這種實現思路和ThreadLocal的實現原理是一樣的、大家有興趣可以去閱讀以下相關原始碼。
三:cglib代理原始碼分析
有了上面的原始碼分析經驗,聰明的小夥伴一定知道cglib代理實際上也差不多,只不過是基於Class類生成的,可以對類進行代理,無需介面,但是內部的實驗邏輯也比較複雜,先上一個簡單的demo
package cglib;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CglibTest implements MethodInterceptor {
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invokeSuper ( obj,args );
}
public String hello(String name){
return "你好" + name;
}
public static void main(String[] args) {
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass (CglibTest.class);
enhancer.setCallback(new CglibTest());
CglibTest cglibTest = (CglibTest) enhancer.create ();
String result = cglibTest.hello ( "張玉龍" );
System.out.println (result);
}
}
執行結果
CGLIB debugging enabled, writing to '/Users/zhangyulong/Downloads'
我被代理了
你好張玉龍
”耳熟能詳“的生成結果,那麼接下來我們看看它到底是怎麼生成的,實現原理和Jdk代理有什麼不同?
我們一層一層的翻原始碼來看看
public Object create() {
classOnly = false;
argumentTypes = null;
return createHelper();
}
classOnly程式碼是否只生成class,不生成代理物件,預設是false,說明要生成物件。argumentType是構造器引數型別,由於我們使用無參構造器,這些引數暫時可以忽略掉。
private Object createHelper() {
preValidate();
Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
ReflectUtils.getNames(interfaces),
filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
callbackTypes,
useFactory,
interceptDuringConstruction,
serialVersionUID);
this.currentKey = key;
Object result = super.create(key);
return result;
}
preValidate 首先驗證一下引數型別以及基礎校驗,cglib支援CallbackFilter,由於我們callBack只有一個,enhancer.setCallback(new CglibTest()); 所以這裡預設沒有filter,看下cglib的處理
private void preValidate() {
if (callbackTypes == null) {
callbackTypes = CallbackInfo.determineTypes(callbacks, false);
validateCallbackTypes = true;
}
if (filter == null) {
if (callbackTypes.length > 1) {
throw new IllegalStateException("Multiple callback types possible but no filter specified");
}
filter = ALL_ZERO;
}
}
private static final CallbackFilter ALL_ZERO = new CallbackFilter(){
public int accept(Method method) {
return 0;
}
};
預設返回0,就是我們傳入的new CglibTest()。重新返回主流程,我們看一下
Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
ReflectUtils.getNames(interfaces),
filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
callbackTypes,
useFactory,
interceptDuringConstruction,
serialVersionUID);
this.currentKey = key;
Object result = super.create(key);
首先根據代理類生成了一個key。這個key的主要作用就是對生成的代理類進行快取,生成程式碼在KeyFactory.create方法。這裡不是主線流程,感興趣的小夥伴自己深入一下即可
public static KeyFactory create(ClassLoader loader, Class keyInterface, KeyFactoryCustomizer customizer,
List<KeyFactoryCustomizer> next) {
Generator gen = new Generator();
gen.setInterface(keyInterface);
if (customizer != null) {
gen.addCustomizer(customizer);
}
if (next != null && !next.isEmpty()) {
for (KeyFactoryCustomizer keyFactoryCustomizer : next) {
gen.addCustomizer(keyFactoryCustomizer);
}
}
gen.setClassLoader(loader);
return gen.create();
}
我們主要看一下AbstractClassGenerator.create方法,這裡也是我們生成代理程式碼的主流程
protected Object create(Object key) {
try {
ClassLoader loader = getClassLoader();
Map<ClassLoader, ClassLoaderData> cache = CACHE;
ClassLoaderData data = cache.get(loader);
if (data == null) {
synchronized (AbstractClassGenerator.class) {
cache = CACHE;
data = cache.get(loader);
if (data == null) {
Map<ClassLoader, ClassLoaderData> newCache = new WeakHashMap<ClassLoader, ClassLoaderData>(cache);
data = new ClassLoaderData(loader);
newCache.put(loader, data);
CACHE = newCache;
}
}
}
this.key = key;
Object obj = data.get(this, getUseCache());
if (obj instanceof Class) {
return firstInstance((Class) obj);
}
return nextInstance(obj);
} catch (RuntimeException e) {
throw e;
} catch (Error e) {
throw e;
} catch (Exception e) {
throw new CodeGenerationException(e);
}
}
聰明的小夥伴已經發現了,cglib代理以及jdk代理的快取結構大同小異。
private static volatile Map<ClassLoader, ClassLoaderData> CACHE = new WeakHashMap<ClassLoader, ClassLoaderData>();
1級快取, ClassLoader以及我們cglib的代理快取物件ClassLoaderData,在ClassLoaderData裡維護了一個弱引用的classloader物件,以及代理類的快取對偶性 LoadingCache。這和JDK代理弱引用classloader幾乎是完全一樣的
public ClassLoaderData(ClassLoader classLoader) {
if (classLoader == null) {
throw new IllegalArgumentException("classLoader == null is not yet supported");
}
this.classLoader = new WeakReference<ClassLoader>(classLoader);
Function<AbstractClassGenerator, Object> load =
new Function<AbstractClassGenerator, Object>() {
public Object apply(AbstractClassGenerator gen) {
Class klass = gen.generate(ClassLoaderData.this);
return gen.wrapCachedClass(klass);
}
};
generatedClasses = new LoadingCache<AbstractClassGenerator, Object, Object>(GET_KEY, load);
}
public ClassLoader getClassLoader() {
return classLoader.get();
}
上面我們講了JDK代理的快取清空的邏輯,那麼我們看下cglib代理物件時,classloader失效後如何處理的,畢竟是弱引用classloader,那麼一定要做快取清空處理的。
ClassLoader classLoader = data.getClassLoader();
if (classLoader == null) {
throw new IllegalStateException("ClassLoader is null while trying to define class " +
getClassName() + ". It seems that the loader has been expired from a weak reference somehow. " +
"Please file an issue at cglib's issue tracker.");
}
cglib的處理還是比較暴力的,直接丟擲異常。接下來我們看下二級快取以及生成位元組碼的處理
public Object get(AbstractClassGenerator gen, boolean useCache) {
if (!useCache) {
return gen.generate(ClassLoaderData.this);
} else {
Object cachedValue = generatedClasses.get(gen);
return gen.unwrapCachedValue(cachedValue);
}
}
useCache來決定是否生成位元組碼後,每次都快取。 我們手動設定就可以了。
/**
* Whether use and update the static cache of generated classes
* for a class with the same properties. Default is <code>true</code>.
*/
public void setUseCache(boolean useCache) {
this.useCache = useCache;
}
/**
* @see #setUseCache
*/
public boolean getUseCache() {
return useCache;
}
Object cachedValue = generatedClasses.get(gen); 快取的邏輯分支,我們接著跟下去。
public V get(K key) {
final KK cacheKey = keyMapper.apply(key);
Object v = map.get(cacheKey);
if (v != null && !(v instanceof FutureTask)) {
return (V) v;
}
return createEntry(key, cacheKey, v);
}
邏輯非常清晰了,先看map中是否有cache物件。有直接拿出來,沒有通過createEntry(key, cacheKey, v)來生成即可。keyMapper.apply(key)是什麼呢,我們看看
private static final Function<AbstractClassGenerator, Object> GET_KEY = new Function<AbstractClassGenerator, Object>() {
public Object apply(AbstractClassGenerator gen) {
return gen.key;
}
};
gen.key就是我們上面提到的KeyFactory生成的key。生成代理物件,並且快取下來
protected V createEntry(final K key, KK cacheKey, Object v) {
FutureTask<V> task;
boolean creator = false;
if (v != null) {
// Another thread is already loading an instance
task = (FutureTask<V>) v;
} else {
task = new FutureTask<V>(new Callable<V>() {
public V call() throws Exception {
return loader.apply(key);
}
});
Object prevTask = map.putIfAbsent(cacheKey, task);
if (prevTask == null) {
// creator does the load
creator = true;
task.run();
} else if (prevTask instanceof FutureTask) {
task = (FutureTask<V>) prevTask;
} else {
return (V) prevTask;
}
}
V result;
try {
result = task.get();
} catch (InterruptedException e) {
throw new IllegalStateException("Interrupted while loading cache item", e);
} catch (ExecutionException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException) {
throw ((RuntimeException) cause);
}
throw new IllegalStateException("Unable to load cache item", cause);
}
if (creator) {
map.put(cacheKey, result);
}
return result;
}
到目前為止,我們快取相關的邏輯都已經講解完畢了,我們把精力放到生成位元組碼部分,最終生成位元組碼的方法如下
protected Class generate(ClassLoaderData data) {
Class gen;
Object save = CURRENT.get();
CURRENT.set(this);
try {
ClassLoader classLoader = data.getClassLoader();
if (classLoader == null) {
throw new IllegalStateException("ClassLoader is null while trying to define class " +
getClassName() + ". It seems that the loader has been expired from a weak reference somehow. " +
"Please file an issue at cglib's issue tracker.");
}
synchronized (classLoader) {
String name = generateClassName(data.getUniqueNamePredicate());
data.reserveName(name);
this.setClassName(name);
}
if (attemptLoad) {
try {
gen = classLoader.loadClass(getClassName());
return gen;
} catch (ClassNotFoundException e) {
// ignore
}
}
byte[] b = strategy.generate(this);
String className = ClassNameReader.getClassName(new ClassReader(b));
ProtectionDomain protectionDomain = getProtectionDomain();
synchronized (classLoader) { // just in case
if (protectionDomain == null) {
gen = ReflectUtils.defineClass(className, b, classLoader);
} else {
gen = ReflectUtils.defineClass(className, b, classLoader, protectionDomain);
}
}
return gen;
} catch (RuntimeException e) {
throw e;
} catch (Error e) {
throw e;
} catch (Exception e) {
throw new CodeGenerationException(e);
} finally {
CURRENT.set(save);
}
}
先使用generateClassName生成代理類的名字,這裡就是我們debug Spring Aop原始碼以及其他原始碼中 帶$符號以及cglib很長的名稱。
private String generateClassName(Predicate nameTestPredicate) {
return namingPolicy.getClassName(namePrefix, source.name, key, nameTestPredicate);
}
最關鍵的生成位元組碼的部分
byte[] b = strategy.generate(this);
public byte[] generate(ClassGenerator cg) throws Exception {
DebuggingClassWriter cw = getClassVisitor();
transform(cg).generateClass(cw);
return transform(cw.toByteArray());
}
protected DebuggingClassWriter getClassVisitor() throws Exception {
return new DebuggingClassWriter(ClassWriter.COMPUTE_FRAMES);
}
public byte[] toByteArray() {
return (byte[]) java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
byte[] b = ((ClassWriter) DebuggingClassWriter.super.cv).toByteArray();
if (debugLocation != null) {
String dirs = className.replace('.', File.separatorChar);
try {
new File(debugLocation + File.separatorChar + dirs).getParentFile().mkdirs();
File file = new File(new File(debugLocation), dirs + ".class");
OutputStream out = new BufferedOutputStream(new FileOutputStream(file));
try {
out.write(b);
} finally {
out.close();
}
if (traceCtor != null) {
file = new File(new File(debugLocation), dirs + ".asm");
out = new BufferedOutputStream(new FileOutputStream(file));
try {
ClassReader cr = new ClassReader(b);
PrintWriter pw = new PrintWriter(new OutputStreamWriter(out));
ClassVisitor tcv = (ClassVisitor)traceCtor.newInstance(new Object[]{null, pw});
cr.accept(tcv, 0);
pw.flush();
} finally {
out.close();
}
}
} catch (Exception e) {
throw new CodeGenerationException(e);
}
}
return b;
}
});
}
}
我們看到這裡可以將生成的程式碼放到指定的位置來方便檢視。這也就是我們demo中設定程式碼生成位置的原因,我們要看看它到底生成了什麼。
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
生成位元組碼的方法在Enhancer中
public void generateClass(ClassVisitor v)
底層是通過asm工具來生成的位元組碼,然後通過構造器反射來生成的程式碼邏輯。由於程式碼生成部分比較複雜,我們忽略這一部分,只關注一下和CallBackFilter相關的內容。
private void emitMethods(final ClassEmitter ce, List methods, List actualMethods) {
...........
MethodInfo method = (MethodInfo)it1.next();
Method actualMethod = (it2 != null) ? (Method)it2.next() : null;
int index = filter.accept(actualMethod);
if (index >= callbackTypes.length) {
throw new IllegalArgumentException("Callback filter returned an index that is too large: " + index);
}
originalModifiers.put(method, new Integer((actualMethod != null) ? actualMethod.getModifiers() : method.getModifiers()));
indexes.put(method, new Integer(index));
List group = (List)groups.get(generators[index]);
if (group == null) {
groups.put(generators[index], group = new ArrayList(methods.size()));
}
group.add(method);
................
}
這裡我們可以看到生成代理類位元組碼時,根據我們傳入的CallbackFilter來決定使用哪個Callback。
看一下到底生成了哪些檔案。
CglibTest$$EnhancerByCGLIB$$fc037646.class
CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181.class
CglibTest$$FastClassByCGLIB$$ef5535a6.class
在目錄中我們發現生成了三個檔案。首先第一個是根據CglibTest原生類來生成的代理類,第二個是原生類的FastClass,第三個是代理類的FastClass
代理類
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import java.lang.reflect.Method;
import net.sf.cglib.core.ReflectUtils;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class CglibTest$$EnhancerByCGLIB$$fc037646 extends CglibTest implements Factory {
private boolean CGLIB$BOUND;
public static Object CGLIB$FACTORY_DATA;
private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
private static final Callback[] CGLIB$STATIC_CALLBACKS;
private MethodInterceptor CGLIB$CALLBACK_0;
private static Object CGLIB$CALLBACK_FILTER;
private static final Method CGLIB$hello$0$Method;
private static final MethodProxy CGLIB$hello$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$intercept$1$Method;
private static final MethodProxy CGLIB$intercept$1$Proxy;
private static final Method CGLIB$equals$2$Method;
private static final MethodProxy CGLIB$equals$2$Proxy;
private static final Method CGLIB$toString$3$Method;
private static final MethodProxy CGLIB$toString$3$Proxy;
private static final Method CGLIB$hashCode$4$Method;
private static final MethodProxy CGLIB$hashCode$4$Proxy;
private static final Method CGLIB$clone$5$Method;
private static final MethodProxy CGLIB$clone$5$Proxy;
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("cglib.CglibTest$$EnhancerByCGLIB$$fc037646");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$equals$2$Method = var10000[0];
CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
CGLIB$toString$3$Method = var10000[1];
CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
CGLIB$hashCode$4$Method = var10000[2];
CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
CGLIB$clone$5$Method = var10000[3];
CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
var10000 = ReflectUtils.findMethods(new String[]{"hello", "(Ljava/lang/String;)Ljava/lang/String;", "intercept", "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;"}, (var1 = Class.forName("cglib.CglibTest")).getDeclaredMethods());
CGLIB$hello$0$Method = var10000[0];
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
CGLIB$intercept$1$Method = var10000[1];
CGLIB$intercept$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;", "intercept", "CGLIB$intercept$1");
}
final String CGLIB$hello$0(String var1) {
return super.hello(var1);
}
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy) : super.hello(var1);
}
final Object CGLIB$intercept$1(Object var1, Method var2, Object[] var3, MethodProxy var4) throws Throwable {
return super.intercept(var1, var2, var3, var4);
}
public final Object intercept(Object var1, Method var2, Object[] var3, MethodProxy var4) throws Throwable {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$intercept$1$Method, new Object[]{var1, var2, var3, var4}, CGLIB$intercept$1$Proxy) : super.intercept(var1, var2, var3, var4);
}
final boolean CGLIB$equals$2(Object var1) {
return super.equals(var1);
}
public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
return var2 == null ? false : (Boolean)var2;
} else {
return super.equals(var1);
}
}
final String CGLIB$toString$3() {
return super.toString();
}
public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
}
final int CGLIB$hashCode$4() {
return super.hashCode();
}
public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
return var1 == null ? 0 : ((Number)var1).intValue();
} else {
return super.hashCode();
}
}
final Object CGLIB$clone$5() throws CloneNotSupportedException {
return super.clone();
}
protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
}
public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return CGLIB$intercept$1$Proxy;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return CGLIB$clone$5$Proxy;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return CGLIB$hello$0$Proxy;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return CGLIB$equals$2$Proxy;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return CGLIB$toString$3$Proxy;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return CGLIB$hashCode$4$Proxy;
}
}
return null;
}
public CglibTest$$EnhancerByCGLIB$$fc037646() {
CGLIB$BIND_CALLBACKS(this);
}
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
CGLIB$THREAD_CALLBACKS.set(var0);
}
public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
CGLIB$STATIC_CALLBACKS = var0;
}
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
CglibTest$$EnhancerByCGLIB$$fc037646 var1 = (CglibTest$$EnhancerByCGLIB$$fc037646)var0;
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}
}
public Object newInstance(Callback[] var1) {
CGLIB$SET_THREAD_CALLBACKS(var1);
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646;
switch(var1.length) {
case 0:
var10000.<init>();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
default:
throw new IllegalArgumentException("Constructor not found");
}
}
public Callback getCallback(int var1) {
CGLIB$BIND_CALLBACKS(this);
MethodInterceptor var10000;
switch(var1) {
case 0:
var10000 = this.CGLIB$CALLBACK_0;
break;
default:
var10000 = null;
}
return var10000;
}
public void setCallback(int var1, Callback var2) {
switch(var1) {
case 0:
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
default:
}
}
public Callback[] getCallbacks() {
CGLIB$BIND_CALLBACKS(this);
return new Callback[]{this.CGLIB$CALLBACK_0};
}
public void setCallbacks(Callback[] var1) {
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
}
static {
CGLIB$STATICHOOK1();
}
}
代理類的FastClass
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import cglib.CglibTest..EnhancerByCGLIB..fc037646;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.reflect.FastClass;
public class CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181 extends FastClass {
public CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181(Class var1) {
super(var1);
}
public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -2055565910:
if (var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
return 3;
}
break;
case -1457535688:
if (var10000.equals("CGLIB$STATICHOOK1()V")) {
return 16;
}
break;
case -1411812934:
if (var10000.equals("CGLIB$hashCode$4()I")) {
return 21;
}
break;
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 14;
}
break;
case -894172689:
if (var10000.equals("newInstance(Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 11;
}
break;
case -879968516:
if (var10000.equals("CGLIB$hello$0(Ljava/lang/String;)Ljava/lang/String;")) {
return 17;
}
break;
case -623122092:
if (var10000.equals("CGLIB$findMethodProxy(Lnet/sf/cglib/core/Signature;)Lnet/sf/cglib/proxy/MethodProxy;")) {
return 0;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return 9;
}
break;
case -419626537:
if (var10000.equals("setCallbacks([Lnet/sf/cglib/proxy/Callback;)V")) {
return 1;
}
break;
case 374345669:
if (var10000.equals("CGLIB$equals$2(Ljava/lang/Object;)Z")) {
return 19;
}
break;
case 560567118:
if (var10000.equals("setCallback(ILnet/sf/cglib/proxy/Callback;)V")) {
return 15;
}
break;
case 811063227:
if (var10000.equals("newInstance([Ljava/lang/Class;[Ljava/lang/Object;[Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 12;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return 13;
}
break;
case 973717575:
if (var10000.equals("getCallbacks()[Lnet/sf/cglib/proxy/Callback;")) {
return 5;
}
break;
case 1115619315:
if (var10000.equals("CGLIB$intercept$1(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 18;
}
break;
case 1221173700:
if (var10000.equals("newInstance([Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 10;
}
break;
case 1230699260:
if (var10000.equals("getCallback(I)Lnet/sf/cglib/proxy/Callback;")) {
return 4;
}
break;
case 1341835395:
if (var10000.equals("main([Ljava/lang/String;)V")) {
return 23;
}
break;
case 1517819849:
if (var10000.equals("CGLIB$toString$3()Ljava/lang/String;")) {
return 20;
}
break;
case 1584330438:
if (var10000.equals("CGLIB$SET_STATIC_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
return 2;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return 6;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return 7;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 8;
}
break;
case 2011844968:
if (var10000.equals("CGLIB$clone$5()Ljava/lang/Object;")) {
return 22;
}
}
return -1;
}
public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 7;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 6;
}
}
}
break;
case -1053468136:
if (var1.equals("getCallbacks")) {
switch(var2.length) {
case 0:
return 5;
}
}
break;
case -981624788:
if (var1.equals("CGLIB$intercept$1")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 18;
}
}
}
break;
case -124978608:
if (var1.equals("CGLIB$equals$2")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 19;
}
}
}
break;
case -60403779:
if (var1.equals("CGLIB$SET_STATIC_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 2;
}
}
}
break;
case -29025554:
if (var1.equals("CGLIB$hashCode$4")) {
switch(var2.length) {
case 0:
return 21;
}
}
break;
case 3343801:
if (var1.equals("main")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Ljava.lang.String;")) {
return 23;
}
}
}
break;
case 85179481:
if (var1.equals("CGLIB$SET_THREAD_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 3;
}
}
}
break;
case 94756189:
if (var1.equals("clone")) {
switch(var2.length) {
case 0:
return 9;
}
}
break;
case 99162322:
if (var1.equals("hello")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 13;
}
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 8;
}
}
break;
case 161998109:
if (var1.equals("CGLIB$STATICHOOK1")) {
switch(var2.length) {
case 0:
return 16;
}
}
break;
case 495524492:
if (var1.equals("setCallbacks")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 1;
}
}
}
break;
case 502538434:
if (var1.equals("intercept")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 14;
}
}
}
break;
case 1154623345:
if (var1.equals("CGLIB$findMethodProxy")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("net.sf.cglib.core.Signature")) {
return 0;
}
}
}
break;
case 1543336190:
if (var1.equals("CGLIB$toString$3")) {
switch(var2.length) {
case 0:
return 20;
}
}
break;
case 1811874389:
if (var1.equals("newInstance")) {
switch(var2.length) {
case 1:
String var10001 = var2[0].getName();
switch(var10001.hashCode()) {
case -845341380:
if (var10001.equals("net.sf.cglib.proxy.Callback")) {
return 11;
}
break;
case 1730110032:
if (var10001.equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 10;
}
}
case 2:
default:
break;
case 3:
if (var2[0].getName().equals("[Ljava.lang.Class;") && var2[1].getName().equals("[Ljava.lang.Object;") && var2[2].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 12;
}
}
}
break;
case 1817099975:
if (var1.equals("setCallback")) {
switch(var2.length) {
case 2:
if (var2[0].getName().equals("int") && var2[1].getName().equals("net.sf.cglib.proxy.Callback")) {
return 15;
}
}
}
break;
case 1891304123:
if (var1.equals("CGLIB$hello$0")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 17;
}
}
}
break;
case 1905679803:
if (var1.equals("getCallback")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("int")) {
return 4;
}
}
}
break;
case 1951977611:
if (var1.equals("CGLIB$clone$5")) {
switch(var2.length) {
case 0:
return 22;
}
}
}
return -1;
}
public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}
public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
fc037646 var10000 = (fc037646)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
return fc037646.CGLIB$findMethodProxy((Signature)var3[0]);
case 1:
var10000.setCallbacks((Callback[])var3[0]);
return null;
case 2:
fc037646.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
return null;
case 3:
fc037646.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
return null;
case 4:
return var10000.getCallback(((Number)var3[0]).intValue());
case 5:
return var10000.getCallbacks();
case 6:
return new Boolean(var10000.equals(var3[0]));
case 7:
return var10000.toString();
case 8:
return new Integer(var10000.hashCode());
case 9:
return var10000.clone();
case 10:
return var10000.newInstance((Callback[])var3[0]);
case 11:
return var10000.newInstance((Callback)var3[0]);
case 12:
return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
case 13:
return var10000.hello((String)var3[0]);
case 14:
return var10000.intercept(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 15:
var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
return null;
case 16:
fc037646.CGLIB$STATICHOOK1();
return null;
case 17:
return var10000.CGLIB$hello$0((String)var3[0]);
case 18:
return var10000.CGLIB$intercept$1(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 19:
return new Boolean(var10000.CGLIB$equals$2(var3[0]));
case 20:
return var10000.CGLIB$toString$3();
case 21:
return new Integer(var10000.CGLIB$hashCode$4());
case 22:
return var10000.CGLIB$clone$5();
case 23:
CglibTest.main((String[])var3[0]);
return null;
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
fc037646 var10000 = new fc037646;
fc037646 var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.<init>();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public int getMaxIndex() {
return 23;
}
}
原生類的FastClass
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.reflect.FastClass;
public class CglibTest$$FastClassByCGLIB$$ef5535a6 extends FastClass {
public CglibTest$$FastClassByCGLIB$$ef5535a6(Class var1) {
super(var1);
}
public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 2;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return 1;
}
break;
case 1341835395:
if (var10000.equals("main([Ljava/lang/String;)V")) {
return 0;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return 3;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return 4;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 5;
}
}
return -1;
}
public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 4;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 3;
}
}
}
break;
case 3343801:
if (var1.equals("main")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Ljava.lang.String;")) {
return 0;
}
}
}
break;
case 99162322:
if (var1.equals("hello")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 1;
}
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 5;
}
}
break;
case 502538434:
if (var1.equals("intercept")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 2;
}
}
}
}
return -1;
}
public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}
public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
CglibTest var10000 = (CglibTest)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
CglibTest.main((String[])var3[0]);
return null;
case 1:
return var10000.hello((String)var3[0]);
case 2:
return var10000.intercept(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 3:
return new Boolean(var10000.equals(var3[0]));
case 4:
return var10000.toString();
case 5:
return new Integer(var10000.hashCode());
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
CglibTest var10000 = new CglibTest;
CglibTest var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.<init>();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public int getMaxIndex() {
return 5;
}
}
我們看下代理類的hello方法
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy) : super.hello(var1);
}
最終呼叫了 var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy)方法,也就是我們的
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invokeSuper ( obj,args );
}
proxy.invokeSuper ( obj,args ) 是怎麼實現的呢,接下來我們重點看看 CGLIB$hello$0$Proxy的生成邏輯。
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) {
MethodProxy proxy = new MethodProxy();
proxy.sig1 = new Signature(name1, desc);
proxy.sig2 = new Signature(name2, desc);
proxy.createInfo = new CreateInfo(c1, c2);
return proxy;
}
這裡根據代理類以及原生類的hello方法生成了方法簽名 Signature。
5個引數分別是 Class c1 目標類Class,Class c2 代理類Class,String desc 代理方法的描述,String name1 被代理方法名,String name2 代理方法名
接下來
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
private void init()
{
/*
* Using a volatile invariant allows us to initialize the FastClass and
* method index pairs atomically.
*
* Double-checked locking is safe with volatile in Java 5. Before 1.5 this
* code could allow fastClassInfo to be instantiated more than once, which
* appears to be benign.
*/
if (fastClassInfo == null)
{
synchronized (initLock)
{
if (fastClassInfo == null)
{
CreateInfo ci = createInfo;
FastClassInfo fci = new FastClassInfo();
fci.f1 = helper(ci, ci.c1);
fci.f2 = helper(ci, ci.c2);
fci.i1 = fci.f1.getIndex(sig1);
fci.i2 = fci.f2.getIndex(sig2);
fastClassInfo = fci;
}
}
}
}
private static class FastClassInfo
{
FastClass f1;
FastClass f2;
int i1;
int i2;
}
private static class CreateInfo
{
Class c1;
Class c2;
NamingPolicy namingPolicy;
GeneratorStrategy strategy;
boolean attemptLoad;
public CreateInfo(Class c1, Class c2)
{
this.c1 = c1;
this.c2 = c2;
AbstractClassGenerator fromEnhancer = AbstractClassGenerator.getCurrent();
if (fromEnhancer != null) {
namingPolicy = fromEnhancer.getNamingPolicy();
strategy = fromEnhancer.getStrategy();
attemptLoad = fromEnhancer.getAttemptLoad();
}
}
}
private static FastClass helper(CreateInfo ci, Class type) {
FastClass.Generator g = new FastClass.Generator();
g.setType(type);
g.setClassLoader(ci.c2.getClassLoader());
g.setNamingPolicy(ci.namingPolicy);
g.setStrategy(ci.strategy);
g.setAttemptLoad(ci.attemptLoad);
return g.create();
}
其實這裡最主要的就是生成代理類和普通類的FastClass,以及hello方法的index,然後去呼叫,我們看一下簡單的例子來看看FastClass底層倒底是什麼
public class FastClass1 {
public void hello(String name) {
System.out.println("hello, " + name);
}
public void hi(String msg) {
System.out.println("hi, " + msg);
}
}
public class FastClass2 {
public Object invoke(Object obj, int methodIndex, Object[] parameters) {
FastClass1 target = (FastClass1)obj;
Object result = null;
switch (methodIndex) {
case 1:
target.hello((String)parameters[0]);
break;
case 2:
target.hi((String)parameters[0]);
break;
}
return result;
}
public int getIndex(String methodDescriptor) {
switch (methodDescriptor.hashCode()) {
case -2084786067:
return 1;
case -70025314:
return 2;
}
return -1;
}
}
public class FastClassTest {
public static void main(String[] args) {
FastClass1 fastClass1 = new FastClass1();
FastClass2 fastClass2 = new FastClass2();
int helloIndex = fastClass2.getIndex("hello(Ljava/lang/String;)V");//方法名(引數型別;...)返回型別
fastClass2.invoke(fastClass1, helloIndex, new Object[]{"張三"});
int hiIndex = fastClass2.getIndex("hi(Ljava/lang/String;)V");
fastClass2.invoke(fastClass1, hiIndex, new Object[]{"cglib動態代理"});
}
}
上例中,FastClass2是FastClass1的Fastclass,在FastClass2中有兩個方法getIndex和invoke。在getIndex方法中對FastClass1的每個方法建立索引,並根據入參(方法名+方法的描述符)來返回相應的索引。invoke根據指定的索引,以parameters為入參呼叫物件obj的方法。這樣就避免了反射呼叫,提高了效率。我們生成的CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181.class以及CglibTest$$FastClassByCGLIB$$ef5535a6.class 原理也是類似。
MethodProxy中invokeSuper 和MethodProxy中invoke的區別是什麼 我們來看看
public Object invoke(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f1.invoke(fci.i1, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
} catch (IllegalArgumentException e) {
if (fastClassInfo.i1 < 0)
throw new IllegalArgumentException("Protected method: " + sig1);
throw e;
}
}
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
fci.f1.invoke(fci.i1, obj, args);執行原生類Fastclass的hello方法
fci.f2.invoke(fci.i2, obj, args);執行代理類FastClass的hello方法
經常有小夥伴不小心用錯的邏輯,導致死迴圈。
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invoke ( obj,args );
}
.........
我被代理了
我被代理了
我被代理了
Exception in thread "main" java.lang.StackOverflowError
at sun.nio.cs.UTF_8.updatePositions(UTF_8.java:77)
at sun.nio.cs.UTF_8.access$200(UTF_8.java:57)
at sun.nio.cs.UTF_8$Encoder.encodeArrayLoop(UTF_8.java:636)
at sun.nio.cs.UTF_8$Encoder.encodeLoop(UTF_8.java:691)
at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:579)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:271)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:129)
at java.io.PrintStream.write(PrintStream.java:526)
at java.io.PrintStream.print(PrintStream.java:669)
at java.io.PrintStream.println(PrintStream.java:806)
at cglib.CglibTest.intercept(CglibTest.java:13)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
.........
為什麼會這樣,因為invokeSuper執行的是代理類的FastClass的方法,invoke是執行的原生類的FastClass的方法,
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
最終執行的方法不一樣,分別是hello以及CGLIB$hello$0
final String CGLIB$hello$1(String var1) {
return super.hello(var1);
}
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$1$Method, new Object[]{var1}, CGLIB$hello$1$Proxy) : super.hello(var1);
}
執行CGLIB$hello$1方法最終呼叫原生方法,執行hello方法會一直執行MethodInterceptor的intercept方法導致死迴圈,最後還有一點攔截器在cglib中可以實現很多型別,這個也是在位元組碼生成程式碼中來實現的,Spring等框架常用的就MethodInterceptor
class CallbackInfo
{
private static final CallbackInfo[] CALLBACKS = {
new CallbackInfo(NoOp.class, NoOpGenerator.INSTANCE),
new CallbackInfo(MethodInterceptor.class, MethodInterceptorGenerator.INSTANCE),
new CallbackInfo(InvocationHandler.class, InvocationHandlerGenerator.INSTANCE),
new CallbackInfo(LazyLoader.class, LazyLoaderGenerator.INSTANCE),
new CallbackInfo(Dispatcher.class, DispatcherGenerator.INSTANCE),
new CallbackInfo(FixedValue.class, FixedValueGenerator.INSTANCE),
new CallbackInfo(ProxyRefDispatcher.class, DispatcherGenerator.PROXY_REF_INSTANCE),
};
}
我們常用的callBack就是MethodInterceptor,但是其他的可能不太常用,他們的區別是什麼呢,來看下面的程式碼
package cglib.callback;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.*;
import java.lang.reflect.Method;
public class CglibTestCallBack {
public String hello0(String name){
return "你好0" + name;
}
public String hello1(String name){
return "你好1" + name;
}
public String hello2(String name){
return "你好2" + name;
}
public String hello3(String name){
return "你好3" + name;
}
public String hello4(String name){
return "你好4" + name;
}
public String hello5(String name){
return "你好5" + name;
}
public String hello6(String name){
return "你好6" + name;
}
public static void main(String[] args) {
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass ( CglibTestCallBack.class);
enhancer.setCallbacks(
new Callback[]{
new DispatcherCallBack(),
new FixedValueCallBack(),
new InvocationHandlerCallback(),
new LazyLoaderCallBack(),
new MethodInterceptorCallBack(),
new NoOpCallBack(),
new ProxyRefDispatcherCallBack()
}
);
enhancer.setCallbackFilter ( new CallbackFilter () {
@Override
public int accept(Method method) {
String name = method.getName ();
if(!name.startsWith ( "hello" )) return 0;
String num = name.substring ( "hello".length () );
return Integer.parseInt ( num );
}
} );
CglibTestCallBack cglibTest = (CglibTestCallBack) enhancer.create ();
String result = cglibTest.hello1 ( "張玉龍" );
System.out.println (result);
}
}
public class DispatcherCallBack implements Dispatcher {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class FixedValueCallBack implements FixedValue {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class InvocationHandlerCallback implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
return null;
}
}
public class LazyLoaderCallBack implements LazyLoader {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class NoOpCallBack implements NoOp {
}
public class ProxyRefDispatcherCallBack implements ProxyRefDispatcher {
@Override
public Object loadObject(Object proxy) throws Exception {
return null;
}
}
我們設定了六個callBack,對應了六個方法 hello0-6, 我們來看看他們生成的代理類的方法是什麼樣的,下面是代理類的部分程式碼
public final String hello0(String var1) {
Dispatcher var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return ((CglibTestCallBack)var10000.loadObject()).hello0(var1);
}
public final String hello1(String var1) {
FixedValue var10000 = this.CGLIB$CALLBACK_1;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_1;
}
return (String)var10000.loadObject();
}
public final String hello2(String var1) {
try {
InvocationHandler var10000 = this.CGLIB$CALLBACK_2;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_2;
}
return (String)var10000.invoke(this, CGLIB$hello2$1, new Object[]{var1});
} catch (Error | RuntimeException var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final String hello3(String var1) {
return ((CglibTestCallBack)this.CGLIB$LOAD_PRIVATE_3()).hello3(var1);
}
private final synchronized Object CGLIB$LOAD_PRIVATE_3() {
Object var10000 = this.CGLIB$LAZY_LOADER_3;
if (var10000 == null) {
LazyLoader var10001 = this.CGLIB$CALLBACK_3;
if (var10001 == null) {
CGLIB$BIND_CALLBACKS(this);
var10001 = this.CGLIB$CALLBACK_3;
}
var10000 = this.CGLIB$LAZY_LOADER_3 = var10001.loadObject();
}
return var10000;
}
public final String hello4(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_4;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_4;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello4$3$Method, new Object[]{var1}, CGLIB$hello4$3$Proxy) : super.hello4(var1);
}
public final String hello6(String var1) {
ProxyRefDispatcher var10000 = this.CGLIB$CALLBACK_6;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_6;
}
return ((CglibTestCallBack)var10000.loadObject(this)).hello6(var1);
}
無需多解釋,生成的程式碼非常清晰了,由於hello5是實現了NoOp,代理類忽略這個方法,直接呼叫原生類的hello5。值得注意的是CGLIB$BIND_CALLBACKS(this);這個方法是這些代理方法中統一的設定callback的方法,我們看看它到底幹了些什麼。
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
CglibTestCallBack$$EnhancerByCGLIB$$58712cb6 var1 = (CglibTestCallBack$$EnhancerByCGLIB$$58712cb6)var0;
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
Callback[] var10001 = (Callback[])var10000;
var1.CGLIB$CALLBACK_6 = (ProxyRefDispatcher)((Callback[])var10000)[6];
var1.CGLIB$CALLBACK_5 = (NoOp)var10001[5];
var1.CGLIB$CALLBACK_4 = (MethodInterceptor)var10001[4];
var1.CGLIB$CALLBACK_3 = (LazyLoader)var10001[3];
var1.CGLIB$CALLBACK_2 = (InvocationHandler)var10001[2];
var1.CGLIB$CALLBACK_1 = (FixedValue)var10001[1];
var1.CGLIB$CALLBACK_0 = (Dispatcher)var10001[0];
}
}
程式碼非常簡單,就是從CGLIB$THREAD_CALLBACKS 或者CGLIB$STATIC_CALLBACKS中獲取callBack陣列,那麼這個陣列我們什麼時候設定的呢?看下面程式碼 net.sf.cglib.proxy.Enhancer#firstInstance
protected Object firstInstance(Class type) throws Exception {
if (classOnly) {
return type;
} else {
return createUsingReflection(type);
}
}
private Object createUsingReflection(Class type) {
setThreadCallbacks(type, callbacks);
try{
if (argumentTypes != null) {
return ReflectUtils.newInstance(type, argumentTypes, arguments);
} else {
return ReflectUtils.newInstance(type);
}
}finally{
// clear thread callbacks to allow them to be gc'd
setThreadCallbacks(type, null);
}
}
private static final String SET_THREAD_CALLBACKS_NAME = "CGLIB$SET_THREAD_CALLBACKS";
private static void setThreadCallbacks(Class type, Callback[] callbacks) {
setCallbacksHelper(type, callbacks, SET_THREAD_CALLBACKS_NAME);
}
特別明顯在初始化時,將我們設定的callBack陣列設定到代理類中,並且在代理類生成例項之後,再清空,方便gc回收,到此cglib的原始碼解析就已經完成了。這裡有一個細節就是上面的程式碼 只有hello4方法才會生成FastClass,所以我們生成的代理類只有1個,沒有生成原生類和代理的FsstClass,這是因為fastclass的生成只有首次呼叫方法的時候,才會去觸發。
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
所以當我們呼叫hello4方法時,首次呼叫就會生成代理類了。這也就是為什麼cglib代理首次呼叫的時候速度會慢一些,因為要先生成位元組碼。
四:手把手寫基於介面的java代理
上面我們分析了jdk動態代理原始碼、cglib代理原始碼、那我們是不是可以自己用自己的方式去寫一個屬於自己的jdk代理呢,答案是可以的
首先我們寫一個基類,當然我並沒有在基類裡面寫什麼東西,只是模擬java中的proxy類而已,當然我們也可以豐富的去拓展一下這個類的方法,來實現更多的功能,讀者可以通過讀完這篇文章之後自己去考慮一下如何來拓展。
1 package meituan.zylproxy.handlder;
2 public class ZylProxy {
3 public ZylProxy(){
4 }
5 }
代理的核心介面,我們去做代理的時候一定是通過反射去呼叫的,不管jdk也好還是cglib也好,永遠也無法脫離反射,我們照貓畫虎,自己寫一個代理介面核心類,這並不是什麼難題,看起來和jdk的核心類介面也沒有什麼區別。
1 package meituan.zylproxy.handlder;
2
3 import java.lang.reflect.Method;
4
5 public interface ZYLInvocationHandler {
6
7 public Object invoke(Object proxy, Method method, Object[] args)
8 throws Exception;
9 }
說明一下 第一個引數proxy是代表代理類,而不是使用者自己寫的原生類實現。引數Method是介面的方法,args是執行時引數列表,在執行時傳遞過來的實際上就是實現類的引數,好了,下面讓我們去深入核心。
我們自定義兩個介面和介面的實現Idto,Idto2,和Dtoimpl如下:
1 package meituan.zylproxy.test.i;
2
3 public interface Idto {
4
5 public void add();
6
7 public String get();
8
9 }
package meituan.zylproxy.test.i;
public interface Idto2 {
public void adda();
public String geta();
}
package meituan.zylproxy.test.i.impl;
import meituan.zylproxy.test.i.Idto;
import meituan.zylproxy.test.i.Idto2;
public class DtoImpl implements Idto,Idto2{
@Override
public void add() {
System.out.println("add");
}
@Override
public String get() {
System.out.println("get");
return "return get";
}
@Override
public void adda() {
System.out.println("adda");
}
@Override
public String geta() {
System.out.println("geta");
return "return geta";
}
}
這是幾個再簡單不過的介面和實現類了,也沒有什麼可說的。接下來我們想對介面進行代理,無非是我們動態將介面進行實現,從而達到對使用者進行自定義handle介面暴露而已,下面看一下我們需要生成一個什麼樣的代理類。
import java.lang.reflect.Method;
import meituan.zylproxy.handlder.ZylProxy;
import meituan.zylproxy.handlder.ZYLInvocationHandler;
import meituan.zylproxy.test.i.Idto;
import meituan.zylproxy.test.i.Idto2;
public class IdtoPorxy extends ZylProxy implements Idto, Idto2 {
public ZYLInvocationHandler zYLInvocationHandler;
public static Method add1;
public static Method get2;
public static Method adda3;
public static Method geta4;
static {
try {
add1 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "add", new Class[0] );
get2 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "get", new Class[0] );
adda3 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "adda", new Class[0] );
geta4 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "geta", new Class[0] );
} catch (Exception e) {
}
}
public IdtoPorxy(ZYLInvocationHandler zYLInvocationHandler) {
this.zYLInvocationHandler = zYLInvocationHandler;
}
public void add() {
Object[] o = {};
try {
this.zYLInvocationHandler.invoke ( this, add1, o );
return;
} catch (Throwable e) {
e.printStackTrace ();
}
}
public java.lang.String get() {
Object[] o = {};
try {
return (java.lang.String) this.zYLInvocationHandler.invoke ( this, get2, o );
} catch (Exception e) {
e.printStackTrace ();
}
return null;
}
public void adda() {
Object[] o = {};
try {
this.zYLInvocationHandler.invoke ( this, adda3, o );
return;
} catch (Throwable e) {
e.printStackTrace ();
}
}
public java.lang.String geta() {
Object[] o = {};
try {
return (java.lang.String) this.zYLInvocationHandler.invoke ( this, geta4, o );
} catch (Exception e) {
e.printStackTrace ();
}
return null;
}
}
這個類不是由使用者寫的,而是我們動態生成的,對於jdk來說是生成了位元組碼,對cglib來說是通過位元組碼增強,其實實現的方式有多種,後面為了更方便大家理解我用字串的形式來動態生成這麼一個"傢伙",先看看這個類幹了些什麼吧,也很簡單。
public class IdtoPorxy extends ZylProxy implements Idto, Idto2
首先是繼承了剛才我們所說的ZylProxy,留著今後拓展,可以參照java的Proxy,然後並且動態的實現了這兩個介面。很簡單
public ZYLInvocationHandler zYLInvocationHandler;
public IdtoPorxy(ZYLInvocationHandler zYLInvocationHandler) {
this.zYLInvocationHandler = zYLInvocationHandler;
}
這個是通過建構函式傳進來一個handler物件,對實現類的操作都靠它了。
public static Method add1;
public static Method get2;
public static Method adda3;
public static Method geta4;
static {
try {
add1 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "add", new Class[0] );
get2 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "get", new Class[0] );
adda3 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "adda", new Class[0] );
geta4 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "geta", new Class[0] );
} catch (Exception e) {
}
}
枚舉出來所有的介面的方法,通過class.forname來獲取到Method元資料。備用
public void add() {
Object[] o = {};
try {
this.zYLInvocationHandler.invoke ( this, add1, o );
return;
} catch (Throwable e) {
e.printStackTrace ();
}
}
public java.lang.String get() {
Object[] o = {};
try {
return (java.lang.String) this.zYLInvocationHandler.invoke ( this, get2, o );
} catch (Exception e) {
e.printStackTrace ();
}
return null;
}
public void adda() {
Object[] o = {};
try {
this.zYLInvocationHandler.invoke ( this, adda3, o );
return;
} catch (Throwable e) {
e.printStackTrace ();
}
}
public java.lang.String geta() {
Object[] o = {};
try {
return (java.lang.String) this.zYLInvocationHandler.invoke ( this, geta4, o );
} catch (Exception e) {
e.printStackTrace ();
}
return null;
}
上面是要枚舉出來所有的方法的實現,很簡單都一個模樣,把實現交給handler去做就可以了。至於怎麼實現靠handler,我們動態生成的這個類只負責委託,不做任何事情。看到這裡大家一定急不可待的想知道這個類怎麼生成的了,我把我寫的原始碼給大家貼出來看一下。
package meituan.zylproxy.util;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import meituan.zylproxy.test.i.Idto;
import meituan.zylproxy.test.i.Idto2;
public class ClassUtil {
public static String mackProxyClass(Class<?> c) throws Exception{
if(!c.isInterface()){
throw new Exception("代理的類必須是介面");
}
StringBuffer importsp = new StringBuffer();
importsp.append("import java.lang.reflect.Method;\n");
importsp.append("import meituan.zylproxy.handlder.ZylProxy;\n");
importsp.append("import meituan.zylproxy.handlder.ZYLInvocationHandler;\n");
importsp.append("import " +c.getName() + ";\n");
StringBuilder publicStaticMethods = new StringBuilder();
//public static Method add;
StringBuilder publicMethods = new StringBuilder();
publicMethods.append("public ZYLInvocationHandler zYLInvocationHandler;\n");
StringBuilder constructorsp = new StringBuilder();
String interFaceName = c.getName().substring(c.getName().lastIndexOf(".")+1);
constructorsp.append("public ").append("" + interFaceName + "Porxy").
append("(ZYLInvocationHandler zYLInvocationHandler) { "
+ "this.zYLInvocationHandler = zYLInvocationHandler;"
+ "}");
publicStaticMethods.append(" static { try { ");
StringBuilder classsp = new StringBuilder();
classsp.append("public class").append(" " + interFaceName + "Porxy").append(" extends ZylProxy implements ").append(interFaceName).append("{");
StringBuilder allMethods = new StringBuilder();
Method[] Methods = c.getMethods();
int curr=0;
for (Method m_:Methods) {
curr++;
publicMethods.append("public static Method ").append(m_.getName() + String.valueOf(curr)).append(";\n");
publicStaticMethods.append("").append(m_.getName() + String.valueOf(curr)).append("=");
publicStaticMethods.append("Class.forName(\"" + c.getName() + "\")" + ".getMethod(\""+ m_.getName() +"\", ");
StringBuilder sp =new StringBuilder();
StringBuilder spArgs = new StringBuilder();
spArgs.append("Object[] o ={");
//public
sp.append(Modifier.toString(m_.getModifiers()).replace("abstract", "")).append(" ");
//void | java.lang.String
sp.append(m_.getReturnType().getName()).append(" ");
//add()|get()
sp.append(m_.getName().concat("("));
StringBuilder methodCLass = new StringBuilder();
if(m_.getParameterTypes().length>0){
Class<?>[] claszz = m_.getParameterTypes();
int methodOffset = 0;
methodCLass.append("new Class[] { ");
for (Class<?> c_ : claszz) {
String paramStr = "obj" + String.valueOf(++methodOffset);
spArgs.append(paramStr.concat(","));
sp.append(c_.getName().toString().concat(" ").concat(paramStr)).append(",");
methodCLass.append("Class.forName(\"" + c_.getName()).append("\"),");
}
sp = new StringBuilder(sp.substring(0, sp.length()-1));
spArgs = new StringBuilder(spArgs.substring(0, spArgs.length()-1));
methodCLass = new StringBuilder(methodCLass.substring(0, methodCLass.length()-1));
}
if(methodCLass.length()>0){
methodCLass.append("}");
} else{
methodCLass.append("new Class[0]");
}
sp.append("){\n");
spArgs.append("}");
sp.append(spArgs+";\n");
if(sp.toString().contains("void")){
sp.append("try {\n this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n return;\n");
sp.append("} catch (Throwable e) {e.printStackTrace();}}");
} else{
sp.append("try {return "
+ "("
+ m_.getReturnType().getName()
+ ")"
+ "this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n");
sp.append("} catch (Exception e) {e.printStackTrace();} return null;");
}
publicStaticMethods.append(methodCLass).append(");\n");
allMethods.append(sp);
}
publicStaticMethods.append("} catch(Exception e){}}");
classsp.append(publicMethods)
.append(publicStaticMethods)
.append(constructorsp).append(allMethods).append("}");
classsp.append("}");
importsp.append(classsp);
return importsp.toString();
}
public static String mackMultiProxyClass(Class<?>[] cs) throws Exception{
StringBuffer importsp = new StringBuffer();
importsp.append("import java.lang.reflect.Method;\n");
importsp.append("import meituan.zylproxy.handlder.ZylProxy;\n");
importsp.append("import meituan.zylproxy.handlder.ZYLInvocationHandler;\n");
StringBuilder publicStaticMethods = new StringBuilder();
publicStaticMethods.append(" static { try { ");
//public static Method add;
StringBuilder publicMethods = new StringBuilder();
publicMethods.append("public ZYLInvocationHandler zYLInvocationHandler;\n");
int curr=0;
StringBuilder constructorsp = new StringBuilder();
String interFaceName = cs[0].getName().substring(cs[0].getName().lastIndexOf(".")+1);
constructorsp.append("public ").append("" + interFaceName + "Porxy").
append("(ZYLInvocationHandler zYLInvocationHandler) { "
+ "this.zYLInvocationHandler = zYLInvocationHandler;"
+ "}");
StringBuilder allMethods = new StringBuilder();
StringBuilder classsp = new StringBuilder();
classsp.append("public class").append(" " + interFaceName + "Porxy").append(" extends ZylProxy implements ");
for (Class<?> c:cs) {
if(!c.isInterface()){
throw new Exception("代理的類必須是介面");
}
classsp.append(c.getName().substring(c.getName().lastIndexOf(".")+1)).append(",");
importsp.append("import " +c.getName() + ";\n");
Method[] Methods = c.getMethods();
for (Method m_:Methods) {
curr++;
publicMethods.append("public static Method ").append(m_.getName() + String.valueOf(curr)).append(";\n");
publicStaticMethods.append("").append(m_.getName() + String.valueOf(curr)).append("=");
publicStaticMethods.append("Class.forName(\"" + c.getName() + "\")" + ".getMethod(\""+ m_.getName() +"\", ");
StringBuilder sp =new StringBuilder();
StringBuilder spArgs = new StringBuilder();
spArgs.append("Object[] o ={");
//public
sp.append(Modifier.toString(m_.getModifiers()).replace("abstract", "")).append(" ");
//void | java.lang.String
sp.append(m_.getReturnType().getName()).append(" ");
//add()|get()
sp.append(m_.getName().concat("("));
StringBuilder methodCLass = new StringBuilder();
if(m_.getParameterTypes().length>0){
Class<?>[] claszz = m_.getParameterTypes();
int methodOffset = 0;
methodCLass.append("new Class[] { ");
for (Class<?> c_ : claszz) {
String paramStr = "obj" + String.valueOf(++methodOffset);
spArgs.append(paramStr.concat(","));
sp.append(c_.getName().toString().concat(" ").concat(paramStr)).append(",");
methodCLass.append("Class.forName(\"" + c_.getName()).append("\"),");
}
sp = new StringBuilder(sp.substring(0, sp.length()-1));
spArgs = new StringBuilder(spArgs.substring(0, spArgs.length()-1));
methodCLass = new StringBuilder(methodCLass.substring(0, methodCLass.length()-1));
}
if(methodCLass.length()>0){
methodCLass.append("}");
} else{
methodCLass.append("new Class[0]");
}
sp.append("){\n");
spArgs.append("}");
sp.append(spArgs+";\n");
if(sp.toString().contains("void")){
sp.append("try {\n this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n return;\n");
sp.append("} catch (Throwable e) {e.printStackTrace();}}");
} else{
sp.append("try {return "
+ "("
+ m_.getReturnType().getName()
+ ")"
+ "this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n");
sp.append("} catch (Exception e) {e.printStackTrace();} return null;}");
}
publicStaticMethods.append(methodCLass).append(");\n");
allMethods.append(sp);
}
}
classsp = new StringBuilder(classsp.substring(0, classsp.length()-1)).append("{");
publicStaticMethods.append("} catch(Exception e){}}");
classsp.append(publicMethods)
.append(publicStaticMethods)
.append(constructorsp).append(allMethods).append("");
classsp.append("}");
importsp.append(classsp);
return importsp.toString();
}
public static void main(String[] args) throws Exception {
System.out.println(mackMultiProxyClass(new Class<?>[]{Idto.class}));
}
}
看起來很複雜,仔細看一下就看了那麼幾個事情,把一個介面class或者多個介面class變成純字串的過程,一共兩個方法,一個是單介面的實現,很早之前寫的,第二個方法是多介面的實現支援多介面,只需要傳一個class物件就會生成代理類的字串,這裡僅僅是字串,需要編譯成class使用。那麼如何編譯成class呢。通過java中的工具類 JavaCompiler很簡單的就可以生成了。我們來看兩個工具類實現
package meituan.zylproxy;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Reader;
import java.io.StringReader;
import java.net.URI;
import java.nio.CharBuffer;
import java.nio.file.WatchEvent.Kind;
import java.util.HashMap;
import java.util.Map;
import javax.tools.FileObject;
import javax.tools.ForwardingJavaFileManager;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
@SuppressWarnings("unchecked")
final class MemoryJavaFileManager extends ForwardingJavaFileManager {
private final static String EXT = ".java";
private Map<String, byte[]> classBytes;
public MemoryJavaFileManager(JavaFileManager fileManager) {
super(fileManager);
classBytes = new HashMap<String, byte[]>();
}
public Map<String, byte[]> getClassBytes() {
return classBytes;
}
public void close() throws IOException {
classBytes = new HashMap<String, byte[]>();
}
public void flush() throws IOException {
}
private static class StringInputBuffer extends SimpleJavaFileObject {
final String code;
StringInputBuffer(String name, String code) {
super(toURI(name), Kind.SOURCE);
this.code = code;
}
public CharBuffer getCharContent(boolean ignoreEncodingErrors) {
return CharBuffer.wrap(code);
}
public Reader openReader() {
return new StringReader(code);
}
}
private class ClassOutputBuffer extends SimpleJavaFileObject {
private String name;
ClassOutputBuffer(String name) {
super(toURI(name), Kind.CLASS);
this.name = name;
}
public OutputStream openOutputStream() {
return new FilterOutputStream(new ByteArrayOutputStream()) {
public void close() throws IOException {
out.close();
ByteArrayOutputStream bos = (ByteArrayOutputStream) out;
classBytes.put(name, bos.toByteArray());
}
};
}
}
public JavaFileObject getJavaFileForOutput(JavaFileManager.Location location,
String className,
JavaFileObject.Kind kind,
FileObject sibling) throws IOException {
if (kind == JavaFileObject.Kind.CLASS) {
return new ClassOutputBuffer(className);
} else {
return super.getJavaFileForOutput(location, className, kind, sibling);
}
}
static JavaFileObject makeStringSource(String name, String code) {
return new StringInputBuffer(name, code);
}
static URI toURI(String name) {
File file = new File(name);
if (file.exists()) {
return file.toURI();
} else {
try {
final StringBuilder newUri = new StringBuilder();
newUri.append("mfm:///");
newUri.append(name.replace('.', '/'));
if (name.endsWith(EXT)) newUri.replace(newUri.length() - EXT.length(), newUri.length(), EXT);
return URI.create(newUri.toString());
} catch (Exception exp) {
return URI.create("mfm:///com/sun/script/java/java_source");
}
}
}
}
package meituan.zylproxy;
import java.io.IOException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
public class DynamicLoader {
public static Map<String, byte[]> compile(String javaSrc) {
Pattern pattern = Pattern.compile("public\\s+class\\s+(\\w+)");
Matcher matcher = pattern.matcher(javaSrc);
if (matcher.find())
return compile(matcher.group(1) + ".java", javaSrc);
return null;
}
public static Map<String, byte[]> compile(String javaName, String javaSrc) {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
StandardJavaFileManager stdManager = compiler.getStandardFileManager(null, null, null);
try (MemoryJavaFileManager manager = new MemoryJavaFileManager(stdManager)) {
JavaFileObject javaFileObject = manager.makeStringSource(javaName, javaSrc);
JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, null, null, Arrays.asList(javaFileObject));
if (task.call())
return manager.getClassBytes();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
public static class MemoryClassLoader extends URLClassLoader {
Map<String, byte[]> classBytes = new HashMap<String, byte[]>();
public MemoryClassLoader(Map<String, byte[]> classBytes) {
super(new URL[0], MemoryClassLoader.class.getClassLoader());
this.classBytes.putAll(classBytes);
}
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] buf = classBytes.get(name);
if (buf == null) {
return super.findClass(name);
}
classBytes.remove(name);
return defineClass(name, buf, 0, buf.length);
}
}
}
通過DynamicLoader的compile方法可以把純字串的str轉成byte[]陣列,有了byte[]陣列就可以很方便的獲取到class物件了,自定義一個MemoryClassLoader通過defineClass方法來獲取到class物件。這樣基本所有的事情都做完了。下面我們寫一個工廠類來獲取代理類。
package meituan.zylproxy.util;
import java.util.Map;
import meituan.zylproxy.DynamicLoader;
import meituan.zylproxy.handlder.ZYLInvocationHandler;
public class PorxyFactory {
//單interface的時候用
public static Object newProxyInstance(Class<?> c,ZYLInvocationHandler h) throws Exception{
String classStr = ClassUtil.mackProxyClass(c);
Map<String, byte[]> m = DynamicLoader.compile(classStr);
DynamicLoader.MemoryClassLoader classLoader = new DynamicLoader.MemoryClassLoader(m);
Class<?> proxy =classLoader.loadClass(m.keySet().toArray(new String[0])[0]);
return proxy.getConstructor(ZYLInvocationHandler.class).newInstance(h);
}
//多interface的時候用
public static Object newProxyInstancewWithMultiClass(Class<?>[] c,ZYLInvocationHandler h) throws Exception{
String classStr = ClassUtil.mackMultiProxyClass(c);
System.out.println (classStr);
Map<String, byte[]> m = DynamicLoader.compile(classStr);
DynamicLoader.MemoryClassLoader classLoader = new DynamicLoader.MemoryClassLoader(m);
Class<?> proxy =classLoader.loadClass(m.keySet().toArray(new String[0])[0]);
return proxy.getConstructor(ZYLInvocationHandler.class).newInstance(h);
}
}
最後一步我們測試一下結果吧,寫一個測試類
package meituan.zylproxy.test;
import meituan.zylproxy.handlder.Hander;
import meituan.zylproxy.test.i.Idto;
import meituan.zylproxy.test.i.impl.DtoImpl;
import meituan.zylproxy.util.PorxyFactory;
public class ZylPorxyTest {
public static void main(String[] args) throws Exception {
Idto d = (Idto) PorxyFactory.newProxyInstancewWithMultiClass(DtoImpl.class.getInterfaces(), new Hander(new DtoImpl()));
d.add();
}
}
很簡單,第一個引數是所有的介面,第二個是handler實現。最後我們看看結果。
大功告成。
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