Mybatis学习之一对一关联查询

 班主任和班级是一对一关系，以此为模型来学习mybatis一对一关联查询

班主任bean对象定义：

package com.mybatis.bean;

public class Teacher {

	private int id;

	private String name;

	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;
	}

}

　　班级bean对象定义：

package com.mybatis.bean;

public class Classes {

	private int id;

	private String name;

	private Teacher teacher;

	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 Teacher getTeacher() {
		return teacher;
	}

	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}

}

　　班级mapper接口定义：

package com.mybatis.inter;

import com.mybatis.bean.Classes;

public interface IClassesOperation {
	public Classes getClasses(int id);
}

　　mybatis配置文件定义：

<?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>
	<!-- 命名别名 -->
	<typeAliases>
		<typeAlias alias="Classes" type="com.mybatis.bean.Classes" />
		<typeAlias alias="Teacher" type="com.mybatis.bean.Teacher" />
	</typeAliases>

	<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://127.0.0.1:3306/test" />
				<property name="username" value="root" />
				<property name="password" value="root" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="com/mybatis/bean/Classes.xml" />
	</mappers>
</configuration>

　　班级SQL映射文件定义，association来实现一对一关联

<?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.mybatis.inter.IClassesOperation">
	<resultMap type="Classes" id="ClassesResultMap">
		<id property="id" column="c_id" />
		<result property="name" column="c_name" />
		<association property="teacher" javaType="Teacher">
			<id property="id" column="t_id" />
			<result property="name" column="t_name" />
		</association>
	</resultMap>

	<select id="getClasses" parameterType="int" resultMap="ClassesResultMap">
		select * from teacher t,class c where t.t_id=c.teacher_id and c.c_id=#{id}
	</select>
</mapper>

　　测试：

package com.mybatis.test;

import java.io.IOException;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.mybatis.bean.Classes;
import com.mybatis.inter.IClassesOperation;
import com.mybatis.util.MybatisUtil;

public class Test {
	public static void main(String[] args) {
		SqlSessionFactory factory=null;
		SqlSession session=null;
		try {
			factory=MybatisUtil.getSqlSessionFactory();
			session=factory.openSession();
			IClassesOperation classesOperation = session.getMapper(IClassesOperation.class);
			Classes classes = classesOperation.getClasses(2);
			System.err.println(classes.getTeacher().getName());
			
		} catch (IOException e) {
			e.printStackTrace();
		}finally {
			session.close();
		}
	}
}