MyBatis多表操作查询功能

MyBatis多表操作查询功能

一对一查询

用户表和订单表的关系为，一个用户多个订单，一个订单只从属一个用户

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

在只查询order表的时候，也要查询user表，所以需要将所有数据全部查出进行封装SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id

创建Order和User实体

order

public class Order {

private int id;

private Date ordertime;

private double total;

//表示当前订单属于哪一个用户

private User user;

user

public class User {

private int id;

private String username;

private String password;

private Date birthday;

创建OrderMapper接口

public interface UserMapper {

//查询全部的方法

public List findAll();

}

配置OrderMapper.xml

SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id

sqlMapConfig.xml

<environments default="developement">

在一对一配置的时候，在order实体中创建了一个user，所以property属性都使用user.** 的方式进行编写，但是这里还可以使用association

SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id

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，一个当但只从属一个用户

一对多查询需求：查询一个用户，与此同时查询出该用户具有的订单

package com.zg.domain;

import java.util.Date;

import java.util.List;

public class User {

private int id;

private String username;

private String password;

private Date birthday;

//描述当前用户存在哪些订单

private List orderList;

public List getOrderList() {

return orderList;

}

public void setOrderList(List orderList) {

this.orderList = orderList;

}

@Override

public String toString() {

return "User{" +

"id=" + id +

", username='" + username + '\'' +

", password='" + password + '\'' +

", birthday=" + birthday +

", orderList=" + orderList +

'}';

}

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 getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

public Date getBirthday() {

return birthday;

}

public void setBirthday(Date birthday) {

this.birthday = birthday;

}

}

修改User实体

package com.zg.domain;

import java.util.Date;

import java.util.List;

public class User {

private int id;

private String username;

private String password;

private Date birthday;

//描述当前用户存在哪些订单

private List orderList;

public List getOrderList() {

return orderList;

}

public void setOrderList(List orderList) {

this.orderList = orderList;

}

@Override

public String toString() {

return "User{" +

"id=" + id +

", username='" + username + '\'' +

", password='" + password + '\'' +

", birthday=" + birthday +

", orderList=" + orderList +

'}';

}

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 getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

public Date getBirthday() {

return birthday;

}

public void setBirthday(Date birthday) {

this.birthday = birthday;

}

}

创建UserMapper接口

package com.zg.mapper;

import com.zg.domain.User;

import java.util.List;

public interface UserMapper {

public List findAll();

}

配置UserMapper.xml

select *,o.id oid from user u,orders o where u.id=o.uid

测试

@Test//测试一对多

public void test2() throws IOException {

InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");

SqlSessionFactory sqlSessionFactory = new http://SqlSessionFactoryBuilder().build(resourceAsStream);

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

List userList = mapper.findAll();

for (User user : userList) {

System.out.println(user);

}

sqlSession.close();

}

多对多查询

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：查询用户同时查询该用户的所有角色

select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userId and ur.roleId=r.id

创建Role实体，修改User实体

添加UserMapper接口

package com.zg.mapper;

import com.zg.domain.User;

import java.util.List;

public interface UserMapper {

public List findAll();

public List findUserAndRoleAll();

}

配置UserMapper.xml

select * from user u,sys_user_role ur ,sys_role r where u.id=ur.userId and ur.roleId=r.id

测试代码

@Test//测试多对多

public void test3() throws IOException {

InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);

SqlSession sqlSession = sqlSessionFactory.openSession();

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

List userAndRoleAll = mapper.findUserAndRoleAll();

for (User user : userAndRoleAll) {

System.out.println(user);

}

sqlSession.close();

}

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。