MyBatis 入门之多对一 association_association多对一-优快云博客

本文介绍了一个使用MyBatis实现一对多关联映射的例子。通过创建Biji表与Users表之间的关联，并利用MyBatis的XML映射文件进行结果集映射，实现了从用户表中获取笔记信息的功能。

1. 新建数据库表Biji，让其与Users表对应，一个user拥有对个biji

userid是外键

2. 新建POJO类--Biji.java

public class Biji {
	
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return super.toString();
	}
	private int bijiid;
	private String bijiname;
	private String content;
	private User user;
	
	public int getBijiid() {
		return bijiid;
	}
	public void setBijiid(int bijiid) {
		this.bijiid = bijiid;
	}
	public String getBijiname() {
		return bijiname;
	}
	public void setBijiname(String bijiname) {
		this.bijiname = bijiname;
	}
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
	public User getUser() {
		return user;
	}
	public void setUser(User user) {
		this.user = user;
	}
	public Biji(int bijiid, String bijiname, String content, User user) {
		super();
		this.bijiid = bijiid;
		this.bijiname = bijiname;
		this.content = content;
		this.user = user;
	}
	public Biji() {
		super();
	}
	
	
	
}

config.xml

<?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>
	<!-- 自动扫描-->
	<typeAliases>
		<typeAlias alias="User" type="com.imut.po.User" />
		<typeAlias alias="Biji" type="com.imut.po.Biji"/>
	</typeAliases>

	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC"/>
			<!--配置数据库连接信息 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
				<property name="username" value="root" />
				<property name="password" value="123,456a" />
			</dataSource>
		</environment>			
	</environments>
	

	
	
	<mappers>
		<mapper resource="com/imut/mapping/userMapper.xml"/>
		<mapper resource="com/imut/mapping/bijiMapper.xml"/>
	</mappers>
</configuration>

3. bijiMapper.xml

<?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.imut.inf.IUser">
	<resultMap id="resultUserBijiList" type="Biji">
		<id property="bijiid" column="bijiid" />
		<result property="bijiname" column="bijiname" />
		<result property="content" column="content" />
		
		<association property="user" javaType="User">
			<id property="id" column="id" />
			<result property="name" column="name" />	
			<result property="age" column="age" />				
		</association>
	</resultMap>
	
	<select id="getUserBijis" parameterType="int" resultMap="resultUserBijiList">
		select u.id , u.name , u.age , b.bijiid , b.bijiname , b.content from users u ,biji b where u.id = b.userid and u.id = #{id}
	</select>
	
	
</mapper>

4. IUser接口中添加方法

public List<Biji> getUserBijis(int userid);

5. 测试类

SqlSession sqlSession = sqlSessionFactory.openSession();
		IUser iuser = sqlSession.getMapper(IUser.class);
		List<Biji> bijis = iuser.getUserBijis(2);
		for(int i = 0;i<bijis.size();i++){
			System.out.println(bijis.get(i).getBijiname());
		}
		sqlSession.close();