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

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 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();
    }

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