package com.ys.po;public class User {	//用户ID	private int id;	//用户姓名	private String username;	//用户性别	private String sex;	public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public String getUsername() {		return username;	}	public void setUsername(String username) {		this.username = username;	}	public String getSex() {		return sex;	}	public void setSex(String sex) {		this.sex = sex;	}	@Override	public String toString() {		return "User [id=" + id + ", username=" + username + ", sex=" + sex				+ "]";	}}

package com.ys.po;public class Orders {	//订单ID	private int id;	//用户ID	private int userId;	//订单数量	private String number;	//和用户表构成一对一的关系，即一个订单只能由一个用户创建	private User user;		public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public int getUserId() {		return userId;	}	public void setUserId(int userId) {		this.userId = userId;	}	public String getNumber() {		return number;	}	public void setNumber(String number) {		this.number = number;	}	public User getUser() {		return user;	}	public void setUser(User user) {		this.user = user;	}	@Override	public String toString() {		return "Orders [id=" + id + ", userId=" + userId + ", number=" + number				+ ", user=" + user + "]";	}}

package one.to.one.mapper;import com.ys.po.Orders;import com.ys.po.User;public interface OrdersMapper {	/**	 * 方式一：嵌套结果	 * select * from orders o,user u where o.user_id=u.id and o.id=#{id}	 * @param orderId	 * @return	 */	//根据订单ID查询订单和用户信息	public Orders selectOrderAndUserByOrderID(int orderId);		/**	 * 方式二：嵌套查询	 * select * from order WHERE id=1;//得到user_id     * select * from user WHERE id=1   //1 是上一个查询得到的user_id的值	 * @param userID	 * @return	 */	//根据订单ID得到订单信息(包含user_id)	public Orders getOrderByOrderId(int orderId);	//根据用户ID查询用户信息	public User getUserByUserId(int userID);}

<?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="one.to.one.mapper.OrdersMapper">	<!-- 	嵌套结果：使用嵌套结果映射来处理重复的联合结果的子集                               封装联表查询的数据(去除重复的数据)     select * from orders o,user u where o.user_id=u.id and o.id=#{id}	 -->	<select id="selectOrderAndUserByOrderID" resultMap="getOrderAndUser">		select * from orders o,user u where o.user_id=u.id and o.id=#{id}	</select>	<resultMap type="com.ys.po.Orders" id="getOrderAndUser">		<!--			id:指定查询列表唯一标识，如果有多个唯一标识，则配置多个id			column:数据库对应的列			property:实体类对应的属性名		  -->		<id column="id" property="id"/>		<result column="user_id" property="userId"/>		<result column="number" property="number"/>		<!--association:用于映射关联查询单个对象的信息			property:实体类对应的属性名			javaType:实体类对应的全类名		  -->		<association property="user" javaType="com.ys.po.User">			<!--				id:指定查询列表唯一标识，如果有多个唯一标识，则配置多个id				column:数据库对应的列				property:实体类对应的属性名			  -->			<id column="id" property="id"/>			<result column="username" property="username"/>			<result column="sex" property="sex"/>		</association>	</resultMap>			<!--         方式二：嵌套查询：通过执行另外一个SQL映射语句来返回预期的复杂类型         select user_id from order WHERE id=1;//得到user_id         select * from user WHERE id=1   //1 是上一个查询得到的user_id的值         property:别名(属性名)    column：列名 -->    <select id="getOrderByOrderId" resultMap="getOrderMap">    	select * from order where id=#{id}    </select>    <resultMap type="com.ys.po.Orders" id="getOrderMap">    	<id column="id" property="id"/>		<result column="number" property="number"/>		<association property="userId"  column="id" select="getUserByUserId">				</association>    </resultMap>    <select id="getUserByUserId" resultType="com.ys.po.User">    	select * from user where id=#{id}    </select>	</mapper>

<?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><!-- 加载数据库属性文件 --><properties resource="db.properties"></properties><!-- 定义别名 --><typeAliases>	<!-- mybatis自动扫描包中的po类，自动定义别名，别名是类名(首字母大写或小写都可以,一般用小写) -->	<package name="com.ys.po"/></typeAliases> <environments default="development">    <environment id="development">      <transactionManager type="JDBC"/>      <!--dataSource 元素使用标准的 JDBC 数据源接口来配置 JDBC 连接对象源  -->      <dataSource type="POOLED">        <property name="driver" value="http://www.mamicode.com/${jdbc.driver}"/>        <property name="url" value="http://www.mamicode.com/${jdbc.url}"/>        <property name="username" value="http://www.mamicode.com/${jdbc.username}"/>        <property name="password" value="http://www.mamicode.com/${jdbc.password}"/>      </dataSource>    </environment>  </environments>    <mappers>         <!-- 通过OrdersMapper接口注册OrdersMapper.xml文件，          	必须保证：接口和xml在同一个包下，而且名字一样         	OrdersMapper接口的方法名和OrdersMapper.xml文件的id一样         	OrdersMapper接口的输出输出参数和OrdersMapper.xml文件resultType，parameterType类型一样         -->         <mapper class="one.to.one.mapper.OrdersMapper"/>   </mappers></configuration>

package one.to.one.mapper;import java.io.InputStream;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import org.junit.Before;import org.junit.Test;import com.ys.po.Orders;public class OneToOneTest {	//定义 SqlSession	SqlSession session =null;		@Before	public void init(){		//定义mybatis全局配置文件		String resource = "mybatis-configuration.xml";		//加载 mybatis 全局配置文件		InputStream inputStream = OneToOneTest.class.getClassLoader()									.getResourceAsStream(resource);		//构建sqlSession的工厂		SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);		//根据 sqlSessionFactory 产生 session		session = sessionFactory.openSession();	}		/**	 * 方式一：嵌套结果	 * select * from orders o,user u where o.user_id=u.id and o.id=#{id}	 */	@Test	public void testSelectOrderAndUserByOrderId(){		String statement = "one.to.one.mapper.OrdersMapper.selectOrderAndUserByOrderID";		//创建OrdersMapper对象，mybatis自动生成mapepr代理对象		OrdersMapper orderMapper = session.getMapper(OrdersMapper.class);		Orders order = orderMapper.selectOrderAndUserByOrderID(1);		System.out.println(order);		session.close();	}		/**	 * 方式二：嵌套查询	 * select * from order WHERE id=1;//得到user_id	 * select * from user WHERE id=1   //1 是上一个查询得到的user_id的值	 */	@Test	public void testgetOrderByOrderId(){		String statement = "one.to.one.mapper.OrdersMapper.getOrderByOrderId";		//创建OrdersMapper对象，mybatis自动生成mapepr代理对象		OrdersMapper orderMapper = session.getMapper(OrdersMapper.class);		Orders order = orderMapper.selectOrderAndUserByOrderID(1);		System.out.println(order);		session.close();	}}

package com.ys.po;import java.util.List;public class User {	//用户ID	private int id;	//用户姓名	private String username;	//用户性别	private String sex;	//一个用户能创建多个订单，用户和订单构成一对多的关系	public List<Orders> orders;		public List<Orders> getOrders() {		return orders;	}	public void setOrders(List<Orders> orders) {		this.orders = orders;	}	public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public String getUsername() {		return username;	}	public void setUsername(String username) {		this.username = username;	}	public String getSex() {		return sex;	}	public void setSex(String sex) {		this.sex = sex;	}	@Override	public String toString() {		return "User [id=" + id + ", username=" + username + ", sex=" + sex				+ "]";	}}

package one.to.many.mapper;import com.ys.po.User;public interface UserMapper {	//根据用户id查询用户信息，以及用户下面的所有订单信息	public User selectUserAndOrdersByUserId(int UserId);}

<?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="one.to.many.mapper.UserMapper">	<!-- 	方式一：嵌套结果：使用嵌套结果映射来处理重复的联合结果的子集                               封装联表查询的数据(去除重复的数据)     select * from user u,orders o where u.id=o.user_id and u.id=#{id}	 -->	<select id="selectUserAndOrdersByUserId" resultMap="getUserAndOrders">		select u.*,o.id oid,o.number number from user u,orders o where u.id=o.user_id and u.id=#{id}	</select>	<resultMap type="com.ys.po.User" id="getUserAndOrders">		<!--id:指定查询列表唯一标识，如果有多个唯一标识，则配置多个id			column:数据库对应的列			property:实体类对应的属性名 -->		<id column="id" property="id"/>		<result column="username" property="username"/>		<result column="sex" property="sex"/>		<!--			property:实体类中定义的属性名			ofType：指定映射到集合中的全类名		  -->		<collection property="orders" ofType="com.ys.po.Orders">			<id column="oid" property="id"/>			<result column="number" property="number"/>		</collection>	</resultMap></mapper>

@Testpublic void testSelectOrderAndUserByOrderId(){	String statement = "one.to.many.mapper.UserMapper.selectUserAndOrdersByUserId";	//创建OrdersMapper对象，mybatis自动生成mapepr代理对象	UserMapper userMapper = session.getMapper(UserMapper.class);	User user = userMapper.selectUserAndOrdersByUserId(1);	System.out.println(user.getOrders().size());	session.close();}

package com.ys.po;import java.util.List;public class Role {	private int id;	private String name;		private List<User> users;	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 List<User> getUsers() {		return users;	}	public void setUsers(List<User> users) {		this.users = users;	}}

package com.ys.po;public class User_Role {	private User user;	private Role role;	public User getUser() {		return user;	}	public void setUser(User user) {		this.user = user;	}	public Role getRole() {		return role;	}	public void setRole(Role role) {		this.role = role;	}}

package many.to.many.mapper;import java.util.List;import com.ys.po.User;public interface UserMapper {		//给定一个角色id，要得到具有这个角色的所有用户信息	public List<User> getUserByRoleId(int roleId);}

<?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="many.to.many.mapper.UserMapper">		<select id="getUserByRoleId" resultMap="getUserMap">		select * from user_role ur,user u where ur.user_id=u.id and ur.role_id=#{id} 	</select>		<resultMap type="com.ys.po.User" id="getUserMap">		<id column="id" property="id"/>		<result column="username" property="username"/>		<result column="sex" property="sex"/>	</resultMap></mapper>

@Testpublic void testGetUserByRoleId(){	String statement = "many.to.many.mapper.UserMapper.getUserByRoleId";	//创建OrdersMapper对象，mybatis自动生成mapepr代理对象	UserMapper userMapper = session.getMapper(UserMapper.class);	List<User> users = userMapper.getUserByRoleId(1);	session.close();}