8.映射关系

1.映射关系
1)<resultMap>
        a)type:实体类的全类名
        b)id:唯一标识
        c)<id>(id字段用该标签修饰)
             a)column:列名称
             b)property:对象属性名称
        d)<result>(非id字段用该标签修饰)
             a)column:列名称
             b)property:对象属性名称
        e)resultMap可以继承
2)返回类型要配置成resultMap

例子：

准备数据库：

1.创建项目

2.建包建配置文件

   com.qf.entity

   com.qf.dao

   com.qf.mapper

   com.qf.utils

   jdbc.properties

   mybatis-config.xml  

3.con.qf.entity包中创建实体类

package com.qf.entity;

import org.apache.ibatis.type.Alias;

public class User {

	private Integer id;
	
	private String name;
	
	private String password;
	
	private String isAdmin;

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getIsAdmin() {
		return isAdmin;
	}

	public void setIsAdmin(String isAdmin) {
		this.isAdmin = isAdmin;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", password=" + password + ", isAdmin=" + isAdmin + "]";
	}
	
}

　　

4.con.qf.dao包中创建接口

package com.qf.dao;

import java.util.List;

import com.qf.entity.User;

public interface IUserDao {

	public User getUserById(Integer id);

	public void add(User user);

	public void delete(Integer id);

	public void update(User user);

	public List<User> getUserList();
}

　　

5.配置jdbc.properties配置文件

jdbc.url =jdbc:mysql://localhost:3306/1707_hibernate
jdbc.name=root
jdbc.password=root
jdbc.driver=com.mysql.jdbc.Driver

　　

配置mybatis-config.xml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">
<configuration>

	<!-- 加载属性文件 
		resource:本地资源文件
	-->
	<properties resource="jdbc.properties"></properties>

	<typeAliases>
			<package name="com.qf.entity"/>
	</typeAliases>

	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="${jdbc.driver}" />
				<property name="url" value="${jdbc.url}" />
				<property name="username" value="${jdbc.name}" />
				<property name="password" value="${jdbc.password}" />
			</dataSource>
		</environment>
	</environments>
	
	
</configuration>

　　

6.com.qf.mapper包创建接口的映射文件

       配置与数据库表映射关系

       配置与IUserDao的关系

<?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">

<!-- namespace指的就是接口的全类名 -->
<mapper namespace="com.qf.dao.IUserDao">


	<resultMap type="com.qf.entity.User" id="userMap2" >
		<result column="is_admin" property="isAdmin"/>
	</resultMap>

	<resultMap type="com.qf.entity.User" id="userMap" extends="userMap2" >
		<id column="id" property="id"/>
		<result column="name" property="name"/>
		<result column="password" property="password"/>
	</resultMap>
	
	<select id="getUserById" resultMap="userMap"> 
		select * from t_user where id = #{id}
	</select>
	
	<!-- parameterType:方法的参数类型  -->
	<insert id="add" parameterType="user">
		insert into t_user (name,password) values(#{name},#{password})
	</insert>
	
	<update id="update">
		update t_user set name = #{name},password = #{password} where id = #{id} 
	</update>
	
	<delete id="delete" parameterType="java.lang.Integer">
		delete from t_user where id = #{id}
	</delete>
	
	<!-- 
		方法返回集合的时候resultType要配置集合中的类型
	 -->
	<select id="getUserList" resultType="user">
		select * from t_user
	</select>
	
	
</mapper>

　　

7.在mybatis-config.xml里面读取Mapper文件

        <!-- Mapper文件 -->
	<mappers>
		<mapper resource="com/qf/mapper/IUserDao.xml" />
	</mappers>

　　

8.com.qf.util工具类

package com.qf.utils;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.xml.sax.InputSource;

public class MyBatisUtil {

	private static SqlSessionFactory sqlSessionFactory;

	public static SqlSessionFactory getSqlSessionFactory() {

		if (sqlSessionFactory == null) {
			initSqlSessionFactory(); // 为空再去参加
		}
		return sqlSessionFactory;
	}

	private static void initSqlSessionFactory() {
		InputStream ips = null;
		try {
			// 1.指定配置文件
			ips = Resources.getResourceAsStream("mybatis-config.xml");

			// 2.赋值操作
			synchronized (MyBatisUtil.class) {
				if (sqlSessionFactory == null) {
					sqlSessionFactory = new SqlSessionFactoryBuilder().build(ips);
				}
			}

		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (ips != null) {
				try {
					ips.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

　　

9.测试类

package com.qf.dao;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.log4j.Logger;
import org.junit.Test;

import com.qf.entity.User;
import com.qf.utils.MyBatisUtil;

public class UserDaoTest {

	private Logger logger = Logger.getLogger(UserDaoTest.class);
	
	@Test
	public void testGetUserById() {
		SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
		
		IUserDao userDao = sqlSession.getMapper(IUserDao.class);
		
		User user = userDao.getUserById(7);
		System.out.println(user);
		sqlSession.close();
	}

}