本文基于Mybatis的动态SQL语句（六）进行功能完善
项目结构图如下：
红框标记的是不需要改动的。
本次案例主要以最为简单的用户和账户的模型来分析Mybatis多表关系。用户为User 表，账户为Account 表。一个用户(User)可以有多个账户(Account)。具体关系如下:
1.创建数据表
在之前的案例中已创建过user表，在这里只需要再创建account表。
DROP TABLE IF EXISTS `account`;
CREATE TABLE `account` (
`ID` int(11) NOT NULL COMMENT '编号',
`UID` int(11) default NULL COMMENT '用户编号',
`MONEY` double default NULL COMMENT '金额',
PRIMARY KEY (`ID`),
KEY `FK_Reference_8` (`UID`),
CONSTRAINT `FK_Reference_8` FOREIGN KEY (`UID`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
insert into `account`(`ID`,`UID`,`MONEY`) values (1,41,1000),(2,45,1000),(3,41,2000);
2.新建实体类
User.java
package com.wd.entity;
import java.util.Date;
import java.util.List;
public class User{
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
//一对多关系映射，主表实体应该包含从表实体的集合引用
List<Account> accounts;
public List<Account> getAccounts() {
return accounts;
}
public void setAccounts(List<Account> accounts) {
this.accounts = accounts;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthyday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
Account.java
package com.wd.entity;
import java.io.Serializable;
public class Account implements Serializable {
private Integer id;
private Integer uid;
private Double money;
//从表实体应该包含一个主表实体的引用
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getUid() {
return uid;
}
public void setUid(Integer uid) {
this.uid = uid;
}
public Double getMoney() {
return money;
}
public void setMoney(Double money) {
this.money = money;
}
@Override
public String toString() {
return "Account{" +
"id=" + id +
", uid=" + uid +
", money=" + money +
'}';
}
}
AccountUser.java
package com.wd.entity;
public class AccountUser extends Account {
private String username;
private String address;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return super.toString() + "AccountUser{" +
"username='" + username + '\'' +
", address='" + address + '\'' +
'}';
}
}
3.新建mapper接口
UserMapper.java
package com.wd.mapper;
import com.wd.entity.User;
import java.util.List;
/**
* 用户的持久层接口
*/
public interface UserMapper {
/**
* 查询所有操作,用时获取用户下所有账户信息
* @return
*/
List<User> findAll();
/**
* 根据id查询用户信息
* @param id
* @return
*/
User findById(Integer id);
}
AccountMapper.java
package com.wd.mapper;
import com.wd.entity.Account;
import com.wd.entity.AccountUser;
import java.util.List;
public interface AccountMapper {
/**
* 查询所有账户,同时还要获取到当前账户的所属用户信息
* @return
*/
List<Account> findAll();
/**
* 查询所有账户，并且带有用户名称和地址信息
* @return
*/
List<AccountUser> findAllAccount();
}
4.新建mapper映射配置文件
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">
<!--namespace必须是mapper的全限定类名-->
<mapper namespace="com.wd.mapper.UserMapper">
<!--定义user的resultMap-->
<resultMap id="userAccountMap" type="user">
<id property="id" column="id"></id>
<result property="username" column="username"></result>
<result property="address" column="address"></result>
<result property="sex" column="sex"></result>
<result property="birthday" column="birthday"></result>
<!-- 配置user对象中accounts集合的映射 -->
<collection property="accounts" ofType="account">
<id column="aid" property="id"></id>
<result column="uid" property="uid"></result>
<result column="money" property="money"></result>
</collection>
</resultMap>
<!--配置查询所有-->
<!--id属性的取值必须是mapper接口的方法名-->
<select id="findAll" resultMap="userAccountMap">
select * from user u left outer join account a on u.id = a.uid
</select>
<!--根据id查询用户信息-->
<select id="findById" parameterType="java.lang.Integer" resultType="com.wd.entity.User">
select * from user where id = #{id}
</select>
</mapper>
AccountMapper.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">
<!--namespace必须是mapper的全限定类名-->
<mapper namespace="com.wd.mapper.AccountMapper">
<!-- 定义封装account和user的resultMap -->
<resultMap id="accountUserMap" type="account">
<id property="id" column="aid"/>
<result property="uid" column="uid"></result>
<result property="money" column="money"></result>
<!-- 一对一的关系映射：配置封装user的内容-->
<association property="user" column="uid" javaType="user">
<id property="id" column="id"/>
<result column="username" property="username"></result>
<result column="address" property="address"></result>
<result column="sex" property="sex"></result>
<result column="birthday" property="birthday"></result>
</association>
</resultMap>
<!--配置查询所有-->
<!--id属性的取值必须是mapper接口的方法名-->
<select id="findAll" resultMap="accountUserMap">
select u.*,a.id as aid,a.uid,a.money from account a , user u where u.id = a.uid;
</select>
<!--查询所有账户信息同时包含用户名和地址信息-->
<select id="findAllAccount" resultType="com.wd.entity.AccountUser">
select a.*, u.username, u.address from account a , user u where u.id = a.uid;
</select>
<!-- <!–根据id查询用户信息–>-->
<!-- <select id="findById" parameterType="java.lang.Integer" resultType="account">-->
<!-- select * from user where id = #{id}-->
<!-- </select>-->
</mapper>
5.新建测试类
UserTest.java
package com.wd.test;
import com.wd.entity.User;
import com.wd.mapper.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class UserTest {
private InputStream in;
private SqlSession session;
private UserMapper userMapper;
@Before //用于在测试方法执行之前执行
public void init() throws IOException {
//1.读取配置文件,生成读取字节流
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
//3.使用工厂生产SqlSession对象
session = factory.openSession();
//4.使用SqlSession创建Mapper代理的接口对象
userMapper = session.getMapper(UserMapper.class);
}
/**
* 释放资源
* @throws IOException
*/
@After //用于在测试方法执行之后执行
public void destroy() throws IOException {
//提交事务
// session.commit();
session.close();
in.close();
}
/**
* 测试查询所有
* @throws Exception
*/
@Test
public void testFindAll(){
List<User> users = userMapper.findAll();
for (User user : users){
System.out.println("--------每个user的信息------------");
System.out.println(user);
System.out.println(user.getAccounts());
}
}
}
AccountTest.java
package com.wd.test;
import com.wd.entity.Account;
import com.wd.entity.AccountUser;
import com.wd.mapper.AccountMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class AccountTest {
private InputStream in;
private SqlSession session;
private AccountMapper accountMapper;
@Before //用于在测试方法执行之前执行
public void init() throws IOException {
//1.读取配置文件,生成读取字节流
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
//3.使用工厂生产SqlSession对象
session = factory.openSession();
//4.使用SqlSession创建Mapper代理的接口对象
accountMapper = session.getMapper(AccountMapper.class);
}
/**
* 释放资源
* @throws IOException
*/
@After //用于在测试方法执行之后执行
public void destroy() throws IOException {
//提交事务
// session.commit();
session.close();
in.close();
}
/**
* 测试查询所有
* @throws Exception
*/
@Test
public void testFindAll(){
List<Account> accounts = accountMapper.findAll();
for (Account account : accounts){
System.out.println("--------每个account的信息------------");
System.out.println(account);
System.out.println(account.getUser());
}
}
/**
* 测试查询所有账户，同时包含用户名称和地址
*/
@Test
public void testFindAllAccountUser(){
List<AccountUser> accountUsers = accountMapper.findAllAccount();
for (AccountUser accountUser : accountUsers){
System.out.println(accountUser);
}
}
/**
* 测试根据id查询用户信息
*/
// @Test
// public void testFindById(){
// User user = userMapper.findById(50);
// System.out.println(user);
// }
}
6.运行结果
UserTest
AccountTest
7.项目源代码
