mybatis（接口的动态代理方式）

港控/mmm° 2022-03-10 03:10 239阅读 0赞

**Mybatis介绍**

> MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。2013年11月迁移到Github。
> 
>   MyBatis是一个优秀的  持久层框架  ，它对jdbc的操作数据库的过程进行封装，使开发者只需要关注 SQL 本身，而不需要花费精力去处理例如注册驱动、创建connection、创建statement、手动设置参数、结果集检索等jdbc繁杂的过程代码。
> 
> Mybatis通过xml或注解的方式将要执行的各种statement（statement、preparedStatemnt、CallableStatement）配置起来，并通过java对象和statement中的sql进行映射生成最终执行的sql语句，最后由mybatis框架执行sql并将结果映射成java对象并返回。

**Mybatis架构**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTY2Nzcy_size_16_color_FFFFFF_t_70][]

**Mapper动态代理方式**

开发规范

> 1.  Mapper.xml文件中的namespace与mapper接口的类路径相同。
> 2.  Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
> 3.  Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql 的parameterType的类型相同
> 4.  Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同

1)UserMapper映射文件

<?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.it.mybatis.mapper.UserMapper">
    	            
    	<select id="findById" parameterType="Integer" resultType="com.it.mybatis.pojo.User">
    		SELECT * FROM user WHERE id = #{id}
    	</select>
    	
    	
    	<select id="findByLikeName" parameterType="String" resultType="com.it.mybatis.pojo.User">
    		select * from user where username like "%"#{username}"%"
    	</select>
    	
    	
    	<insert id="saveUser" parameterType="com.it.mybatis.pojo.User">
            
     		<selectKey keyColumn="id" keyProperty="id" order="AFTER" resultType="Integer">
     			select LAST_INSERT_ID()
     		</selectKey>
    		insert into user(username,birthday,sex,address) 
    			values(#{username},#{birthday},#{sex},#{address})
    	</insert>
    	
    	
    	<update id="updateUser" parameterType="com.it.mybatis.pojo.User">
    		update user set username = #{username},sex = #{sex},address = #{address} where id = #{id}
    	</update>
    	
    	
    	<delete id="deleteUserById" parameterType="com.it.mybatis.pojo.User">
    		delete from user where id =#{id}
    	</delete>
    
    </mapper>

2)UserMapper接口文件(注意**规范**)

public interface UserMapper {
    	
    	User findById(Integer id);
    	
    	List<User> findByLikeName(String username);
    	
    	void saveUser(User user);
    	
    	void updateUser(User user);
    	
    	void deleteUserById(Integer id);
    	
    	
    }

3)SqlMapConfig.xml文件(加载usermapper.xml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">
    <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?characterEncoding=utf-8" />
    				<property name="username" value="root" />
    				<property name="password" value="admin" />
    			</dataSource>
    		</environment>
    	</environments>
    	
    	<mappers>
    		<mapper resource="com/it/mybatis/pojo/User.xml"/>
    	</mappers>
    	
    </configuration>

4)测试

public class MapperTest {
        //根据ID查询
    	@Test
    	public void func1() throws IOException {
    		// 1. 创建SqlSessionFactoryBuilder对象
    		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    		// 2. 加载SqlMapConfig.xml配置文件
    		InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    		// 3. 创建SqlSessionFactory对象
    		SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
    		// 4. 创建SqlSession对象
    		SqlSession openSession = build.openSession();
    		
    		UserMapper mapper = openSession.getMapper(UserMapper.class);
    		
    		User user = mapper.findById(10);
    		System.out.println(user);
    	}
    
        //根据username模糊查询
    	@Test
    	public void func2() throws IOException {
    		// 1. 创建SqlSessionFactoryBuilder对象
    		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    		// 2. 加载SqlMapConfig.xml配置文件
    		InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    		// 3. 创建SqlSessionFactory对象
    		SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
    		// 4. 创建SqlSession对象
    		SqlSession openSession = build.openSession();
    		
    		UserMapper mapper = openSession.getMapper(UserMapper.class);
    		
    		List<User> user = mapper.findByLikeName("j");
    		for (User user2 : user) {
    			System.out.println(user2);
    		}
    	}
    
        //插入User
    	@Test
    	public void func3() throws IOException {
    		// 1. 创建SqlSessionFactoryBuilder对象
    		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    		// 2. 加载SqlMapConfig.xml配置文件
    		InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    		// 3. 创建SqlSessionFactory对象
    		SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
    		// 4. 创建SqlSession对象
    		SqlSession openSession = build.openSession();
    		
    		UserMapper mapper = openSession.getMapper(UserMapper.class);
    		User user = new User();
    		user.setAddress("address");
    		user.setBirthday(new Date());
    		user.setSex("1");
    		user.setUsername("jackson");
    		
    		mapper.saveUser(user);
    		
    		openSession.commit();
    	}
    
        //更新
    	@Test
    	public void func4() throws IOException {
    		// 1. 创建SqlSessionFactoryBuilder对象
    		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    		// 2. 加载SqlMapConfig.xml配置文件
    		InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    		// 3. 创建SqlSessionFactory对象
    		SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
    		// 4. 创建SqlSession对象
    		SqlSession openSession = build.openSession();
    		
    		UserMapper mapper = openSession.getMapper(UserMapper.class);
    		User user = new User();
    		user.setId(31);
    		user.setAddress("address22");
    		user.setSex("2");
    		user.setUsername("jackson2222");
    		
    		mapper.updateUser(user);
    		
    		openSession.commit();
    	}
    
        //删除
    	@Test
    	public void func5() throws IOException {
    		// 1. 创建SqlSessionFactoryBuilder对象
    		SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
    		// 2. 加载SqlMapConfig.xml配置文件
    		InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    		// 3. 创建SqlSessionFactory对象
    		SqlSessionFactory build = sqlSessionFactoryBuilder.build(resourceAsStream);
    		// 4. 创建SqlSession对象
    		SqlSession openSession = build.openSession();
    		
    		UserMapper mapper = openSession.getMapper(UserMapper.class);
    		
    		
    		mapper.deleteUserById(31);
    		
    		openSession.commit();
    	}
    
    }

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