第一个mybatis程序
2、第一个mybatis程序
思路:搭建环境--->导入mybatis--->编写代码--->测试!
2.1、搭建环境
搭建数据库
CREATE DATABASE `mybatis`; USE `mybatis`; INSERT INTO `user`(`id`,`name`,`pwd`)VALUES (1,'张三','123456'), (2,'李四','123456'), (3,'王五','123545');
新建项目
- 新建一个普通的maven项目
- 删除src目录(成为父工程)
2.2、导入依赖
<dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.13.2</version> <scope>test</scope> </dependency> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.25</version> </dependency> <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.7</version> </dependency>
2.3、创建一个模块
- 编写mybatis核心配置文件
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--核心配置文件--> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="${com.mysql.jdbc.Driver"/> <property name="url" value="${jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&CharacterEncoding=UTF-8}"/> <property name="username" value="${root}"/> <property name="password" value="${root}"/> </dataSource> </environment> </environments> <mappers> <mapper resource="org/mybatis/example/BlogMapper.xml"/> </mappers> </configuration>
- 编写mybatis工具类
public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory; static{ try { //获取SqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } //既然有了SqlSessionFactory对象,我们就可以获得SqlSession的实例了 //SqlSession完全包含了面向数据库执行SQL命令所需的所有方法 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }
2.4、编写代码
- 实体类
public class User { private int id; private String name; private String pwd; public User() { } public User(int id, String name, String pwd) { this.id = id; this.name = name; this.pwd = pwd; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPwd() { return pwd; } public void setPwd(String pwd) { this.pwd = pwd; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwd='" + pwd + '\'' + '}'; } }
- Dao接口
public interface UserDao { List<User> getUserList(); }
- 接口实现类由原来的UserDaoImpl变为现在的UserMapper
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.kuang.dao.UserDao"> <select id="getUserList" resultType="com.kuang.pojo.User"> select * from mybatis.user </select> </mapper>
2.5、测试
- Junit测试
public class UserDaoTest { @Test public void test(){ SqlSession sqlSession = MybatisUtils.getSqlSession(); UserDao userDao = sqlSession.getMapper(UserDao.class); List<User> userList = userDao.getUserList(); for (User user : userList) { System.out.println(user); } sqlSession.close(); } }
这里的测试问题真的是百出!!!把我折腾了有半天
- 一定要记住在核心配置中注册UserMapper,并且以这种格式,不然会报错,显示没有注册
<mappers> <mapper resource="com/kuang/dao/UserMapper.xml"/> </mappers>
- 由于maven的约定大于限制,我写的UserMapper.xml文件一定要在子父工程的pom.xml中添加这个,
<build> <resources> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> </resources> </build>
- 再就是遇到了一个奇葩中的奇葩问题,我一运行代码就报错,检查了所有代码没有任何问题,该更新的也都更新了,结果还是报错,结果最后在右边栏maven中点了个generate sources问题就解决了,我现在还不明白,整的我一头雾水。
「其他文章」
- 详解CVE-2022-0847 DirtyPipe漏洞
- 用「闪电侠」的例子解释一下进程和线程
- Fluent-Validator 业务校验器
- Java 统计新客户
- 【Java面试】Redis存在线程安全问题吗?为什么?
- 其实 Gradle Transform 就是个纸老虎 —— Gradle 系列(4)
- drools的类型声明(Type declarations)
- JavaScript中if语句优化和部分语法糖小技巧推荐
- Spring Boot 微信小程序_保存微信登录者的个人信息
- Arthas常用功能及一次线上问题排查
- 用 Go 快速开发一个 RESTful API 服务
- GitHub 毕业年鉴「GitHub 热点速览 v.22.20」
- docker 1.2 之docker基本用法
- Linux-Mycat实现MySQL的读写分离
- 工具14Finger-全能web指纹识别与分享平台
- CMake技术总结
- vue - Vue路由(扩展)
- C# WPF后台动态添加控件(经典)
- WPF中的依赖属性
- 关于Spring中的useSuffixPatternMatch