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MPJBaseMapper 如何使用外连接 mapper接口怎么写

Mapper代理接口(动态代理,有接口的情况,mybatis自动是生成实现类)
只需要写Mapper接口,相当于dao接口
1) 需要编写mapper.xml, Mapper接接口,Mapper接口需要遵循一些开发规范,Mybatis自动生成Mapper接口实现类的代理对象
2)4个开发规范
a)mapper.xml中namespace要等于接口的地址(全路径,包.类名)
b)mapper接口中的方法名要与mapper.xml文件中statement的id名称相同
c)mapper接口中方法的输入参数类型要与mapper.xml文件中statement的输入类型相同
d) mapper接口中方法的返回值类型要与mapper.xml文件中语句标签的返回值类型相同

Mapper接口:

/**
 * User的Mapper接口
 * @author Administrator
 *
 */
public interface UserMapper {

	//根据id查找用户
	public User findUserById(int id) throws Exception;
	
	//添加用户
	public void insertUser(User user);
	
	查询所有用户
	public List<User> findAllUser();
	
	//根据id删除用户
	public void deleteUser(int id);
	
	//修改用户昵称
	public void updateNickname(User user);
	
	//查询姓x的用户的个数
	public int selectCount(String name);
	
}

mapper.xml:

<!-- mapper标签需要指定namespace属性,项目中属性值唯一 -->
<mapper namespace="com.mybatis.mapper.inter.UserMapper">
	<!-- 根据id查找用户 -->
	<!-- id:代表当前文件中查询的id,id在当前文件中唯一;
		 parameterType:用于指定输入参数的类型,可不写;
		 resultType:用于指定返回参数的类型,可不写 -->
	<select id="findUserById" parameterType="int" resultType="com.mybatis.entity.User">
	select * from user where id = #{id}
	</select>
	
	<!-- 查询所有用户 -->
	<select id="findAllUser" resultType="com.mybatis.entity.User">
	select * from user
	</select>
	
	<!-- 添加用户 -->
	<insert id="insertUser" parameterType="com.mybatis.entity.User">
		<!-- 将插入的主键返回,返回到输入参数的对象中 -->
		<!-- keyProperty:将查询到的主键值设置到parameterType指定的对象的那个属性
		     order:是相对于insert语句来说它的执行顺序
		     resultType:用于指定返回参数的类型 -->
		<selectKey keyProperty="id" order="AFTER" resultType="int">
		<!-- 获取刚刚插入的记录的主键 -->
		select LAST_INSERT_ID()
		</selectKey>
	insert into user(name,age,nickname) values(#{name},#{age},#{nickname})
	</insert>
	
	<!-- 删除用户 -->
	<delete id="deleteUser" parameterType="int">
	delete from user where id=#{id}
	</delete>
	
	<!-- 配置用户昵称 -->
	<update id="updateNickname" parameterType="com.mybatis.entity.User">
	update user set nickname=#{nickname} where id=#{id}
	</update>
	
	<!-- /查询姓x的用户的个数 -->
	<select id="selectCount" parameterType="java.lang.String" resultType="int">
	<!-- 解析时候,name传入李,#会自动加上单引号'李'
	name' and pwd='123
	                      $  李   update set name=''-->
	
	select count(id) from user where name like #{name}"%"
	</select>
</mapper>

test.java:

public class test{
	//SqlSessionFactory单例对象,一旦创建,不再销毁,一直使用这个实例
	private SqlSessionFactory factory;
	
	@Before//初始化方法,每个测试方法之前都要执行一次
	public void before() throws Exception{
		//1、得到配置文件流
		InputStream  inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
		//2、创建会话工厂
		factory = new SqlSessionFactoryBuilder().build(inputStream);
	}

	/*
	 * SqlSession最佳应用场合,是在方法体内,定义成一个局部变量,让每个对象都有自己的独立区域,多线程影响不到
	 */
	@org.junit.Test
	public void testFindById() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		User user = mapper.findUserById(6);
		System.out.println(user);
		
		//5、释放资源
		session.close();
	}
	
	@org.junit.Test
	public void testInsertUser() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		User user = new User();
		user.setName("礼拜");
		user.setAge(20);
		user.setNickname("jjfiejfe");
		mapper.insertUser(user);
		System.out.println(user);
		
		session.commit();
		
		//5、释放资源
		session.close();
	}
	
	@org.junit.Test
	public void testFindAllUser() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		List<User> list = mapper.findAllUser();
		for (User user : list) {
			System.out.println(user);
		}
		
		//5、释放资源
		session.close();
	}
	
	@org.junit.Test
	public void testDeleteUser() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		mapper.deleteUser(14);
		
		session.commit();
		
		//5、释放资源
		session.close();
	}
	

	@org.junit.Test
	public void testUpdateNickname() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		User user = new User();
		user.setId(15);
		user.setNickname("jack");
		mapper.updateNickname(user);
		System.out.println(user);
		
		session.commit();
		
		//5、释放资源
		session.close();
	}
	
	@org.junit.Test
	public void testUserCount() throws Exception{
		//3、通过工厂得到会话
		SqlSession session = factory.openSession();
		
		//获取到Mapper接口
		UserMapper mapper = session.getMapper(UserMapper.class);
		int count = mapper.selectCount("王");
		System.out.println(count);
		
		//5、释放资源
		session.close();
	}

}



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