五、Mybatis复杂映射开发
1.一对一查询
1.1 一对一查询的模型
用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户
一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户
SQL:
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(50) DEFAULT NULL,
`password` varchar(50) DEFAULT NULL,
`birthday` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
INSERT INTO `user` VALUES ('1', 'lucy', '123', '2019-12-12');
INSERT INTO `user` VALUES ('2', 'tom','123', '2019-12-12');
DROP TABLE IF EXISTS `orders`;
CREATE TABLE `orders` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`ordertime` varchar(255) DEFAULT NULL,
`total` double DEFAULT NULL,
`uid` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `uid` (`uid`),
CONSTRAINT `orders_ibfk_1` FOREIGN KEY (`uid`) REFERENCES `user` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
INSERT INTO `orders` VALUES ('1', '2019-12-12', '3000', '1');
INSERT INTO `orders` VALUES ('2', '2019-12-12', '4000', '1');
INSERT INTO `orders` VALUES ('3', '2019-12-12', '5000', '2');
1.2 一对一查询的语句
对应的sql语句： select * from orders o,user u where o.uid=u.id;
1.3 创建Order和User实体
package com.cookie.pojo;
import java.util.Date;
public class User {
private Integer id;
private String username;
private String password;
private Date birthday;
}
package com.cookie.pojo;
import java.util.Date;
public class Order {
private int id;
private Date orderTime;
private double total;
//代表当前订单从属于哪⼀个客户
private User user;
}
1.4 创建OrderMapper接口
package com.cookie.mapper;
import com.cookie.pojo.Order;
import java.util.List;
public interface OrderMapper {
List<Order> findAll();
}
1.5 配置OrderMapper.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>
<!--加载外部properties-->
<properties resource="jdbc.properties"></properties>
<environments default="development">
<environment id="development">
<!--当前事务交给JDBC处理-->
<transactionManager type="JDBC"/>
<!--当前使用mybatis提供的连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///cookie"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!--引入映射配置文件-->
<mappers>
<mapper resource="OrderMapper.xml"/>
</mappers>
</configuration>
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql:///test
jdbc.username=root
jdbc.password=123456
<?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.cookie.mapper.OrderMapper">
<resultMap id="orderMap" type="com.cookie.pojo.Order">
<result property="id" column="id"></result>
<result property="orderTime" column="orderTime"></result>
<result property="total" column="total"></result>
<association property="user" javaType="com.cookie.pojo.User">
<result property="id" column="uid"></result>
<result property="username" column="username"></result>
<result property="password" column="password"></result>
<result property="birthday" column="birthday"></result>
</association>
</resultMap>
<select id="findAll" resultMap="orderMap">
select * from orders o,user u where o.uid=u.id
</select>
</mapper>
还可以这样配置：
<resultMap id="orderMap" type="com.cookie.pojo.Order">
<result property="user.id" column="uid"></result>
<result property="user.username" column="username"></result>
<result property="user.password" column="password"></result>
<result property="user.birthday" column="birthday"></result>
</resultMap>
测试:
@Test
public void test1() throws IOException {
//加载核⼼配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);
List<Order> all = mapper.findAll();
for (Order order : all) {
System.out.println(order);
}
sqlSession.close();
}
2.一对多查询
2.1 一对多查询的模型
用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户
一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单 
2.2 一对多查询的语句
对应的sql语句： select u.*,o.id oid,o.ordertime,o.total,o.uid from user u left join orders o on u.id=o.uid;
2.3 实体类
public class User {
private Integer id;
private String username;
private String password;
private Date birthday;
//代表当前⽤户具备哪些订单
private List<Order> orderList;
}
2.4 创建UserMapper接口
package com.cookie.mapper;
import com.cookie.pojo.User;
import java.util.List;
public interface UserMapper {
List<User> findAll();
}
2.5 配置UserMapper.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.cookie.mapper.UserMapper">
<resultMap id="userMap" type="com.cookie.pojo.User">
<result property="id" column="id"></result>
<result property="username" column="username"></result>
<result property="password" column="password"></result>
<result property="birthday" column="birthday"></result>
<collection property="orderList" ofType="com.cookie.pojo.Order">
<result property="id" column="oid"></result>
<result property="orderTime" column="orderTime"></result>
<result property="total" column="total"></result>
</collection>
</resultMap>
<select id="findAll" resultMap="userMap">
select u.*,o.id oid,o.ordertime,o.total,o.uid from user u left join orders o on u.id=o.uid;
</select>
</mapper>
测试：
@Test
public void test2() throws IOException {
//加载核⼼配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAll();
for (User user : all) {
System.out.println(user);
}
sqlSession.close();
}
3.多对多查询
3.1 多对多查询的模型
用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用
多对多查询的需求：查询用户同时查询出该用户的所有角色
SQL：
DROP TABLE IF EXISTS `sys_role`;
CREATE TABLE `sys_role` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`rolename` varchar(255) DEFAULT NULL,
`roleDesc` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
INSERT INTO `sys_role` VALUES ('1', 'CTO', 'CTO');
INSERT INTO `sys_role` VALUES ('2', 'CEO', 'CEO');
DROP TABLE IF EXISTS `sys_user_role`;
CREATE TABLE `sys_user_role` (
`userid` int(11) NOT NULL,
`roleid` int(11) NOT NULL,
PRIMARY KEY (`userid`,`roleid`),
KEY `roleid` (`roleid`),
CONSTRAINT `sys_user_role_ibfk_1` FOREIGN KEY (`userid`) REFERENCES `user` (`id`),
CONSTRAINT `sys_user_role_ibfk_2` FOREIGN KEY (`roleid`) REFERENCES `sys_role` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `sys_user_role` VALUES ('1', '1');
INSERT INTO `sys_user_role` VALUES ('2', '1');
INSERT INTO `sys_user_role` VALUES ('1', '2');
INSERT INTO `sys_user_role` VALUES ('2', '2');
3.2 多对多查询的语句
select * from user u left join sys_user_role ur on u.id = ur.userid left join sys_role r on r.id = ur.roleid;
3.3 创建Role实体，修改User实体
package com.cookie.pojo;
public class Role {
private Integer id;
private String roleName;
private String roleDesc;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getRoleName() {
return roleName;
}
public void setRoleName(String roleName) {
this.roleName = roleName;
}
public String getRoleDesc() {
return roleDesc;
}
public void setRoleDesc(String roleDesc) {
this.roleDesc = roleDesc;
}
@Override
public String toString() {
return "Role{" +
"id=" + id +
", roleName='" + roleName + '\'' +
", roleDesc='" + roleDesc + '\'' +
'}';
}
}
public class User {
private Integer id;
private String username;
private String password;
private Date birthday;
//代表当前用户具备哪些订单
private List<Order> orderList;
//代表当前用户具备哪些角色
private List<Role> roleList;
}
3.4 添加UserMapper接口方法
public interface UserMapper {
List<User> findAll();
List<User> findAllUserAndRole();
}
3.5 配置UserMapper.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.cookie.mapper.UserMapper">
<resultMap id="userMap" type="com.cookie.pojo.User">
<result property="id" column="id"></result>
<result property="username" column="username"></result>
<result property="password" column="password"></result>
<result property="birthday" column="birthday"></result>
<collection property="orderList" ofType="com.cookie.pojo.Order">
<result property="id" column="oid"></result>
<result property="orderTime" column="orderTime"></result>
<result property="total" column="total"></result>
</collection>
</resultMap>
<resultMap id="userRoleMap" type="com.cookie.pojo.User">
<result property="id" column="userid"></result>
<result property="username" column="username"></result>
<result property="password" column="password"></result>
<result property="birthday" column="birthday"></result>
<collection property="roleList" ofType="com.cookie.pojo.Role">
<result property="id" column="roleid"></result>
<result property="roleName" column="rolename"></result>
<result property="roleDesc" column="roleDesc"></result>
</collection>
</resultMap>
<select id="findAll" resultMap="userMap">
select u.*,o.id oid,o.ordertime,o.total,o.uid from user u left join orders o on u.id=o.uid;
</select>
<select id="findAllUserAndRole" resultMap="userRoleMap">
select * from user u left join sys_user_role ur on u.id = ur.userid left join sys_role r on r.id = ur.roleid;
</select>
</mapper>
测试：
@Test
public void test3() throws IOException {
//加载核⼼配置文件
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAllUserAndRole();
for (User user : all) {
System.out.println(user);
}
sqlSession.close();
}