一对一

扩展

创建Orders的扩展类OrdersExtend，添加要查找的user表里的字段

package com.company.model;public class OrdersExtend extends Orders {    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 "OrdersExtend{" +                "username='" + username + '\'' +                ", address='" + address + '\'' +                '}' + super.toString();    }}

OrdersMapper.xml

    
        
             SELECT o.*,u.username,u.address        FROM orders o ,user u        WHERE o.user_id = u.id        and o.id = #{id}    
    

@Test    public void func8() throws IOException {        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        SqlSession session = sessionFactory.openSession();        OrdersMapper ordersMapper = session.getMapper(OrdersMapper.class);        OrdersExtend order = ordersMapper.getOrderById(3);        // OrdersExtend{username='王五', address='null'}Orders{id=3, user_id=1, number='1000010', createtime=Wed Feb 04 13:22:35 CST 2015, note='null'}    }

模型

模型Orders里添加User属性

            
             
             
             
             
                 
                  
                  
              
         
                SELECT o.*,u.username,u.address        FROM orders o ,user u        WHERE o.user_id = u.id        and o.id = #{id}    

@Test    public void func8() throws IOException {        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        SqlSession session = sessionFactory.openSession();        OrdersMapper ordersMapper = session.getMapper(OrdersMapper.class);        Orders order = ordersMapper.getOrderById2(3);        // Orders{id=0, user_id=0, number='null', createtime=null, note='null', user=User{id=1, username='王五', sex='null', birthday=null, address='null'}}    }

一对多

模型Orders里添加OrderDetail属性 

private List
    
      orderDetails;
    

OrdersMapper.xml

            
             
             
             
             
                 
                  
                  
              
             
                 
                  
                  
              
         
                SELECT           o.*,           u.username,           u.address,           od.id detail_id,           od.items_id,           od.items_num        FROM           orders o,           user u,           orderdetail od        WHERE           o.user_id = u.id           and o.id = od.orders_id           and o.id = #{id}    

多对多

UserMapper.xml

            
             
             
             
                 
                  
                  
                  
                  
                  
                      
                       
                       
                       
                           
                            
                            
                            
                        
                   
              
         
                SELECT           user.id,           user.username,           user.address,           orders.id order_id,           orders.number,           orders.createtime,           orders.note,           orders.number,           orderdetail.id detail_id,           orderdetail.items_id ,           orderdetail.items_num ,           items.name,           items.detail,           items.price        FROM           user,           orders,           orderdetail,           items        WHERE           orders.user_id = user.id           and orders.id = orderdetail.orders_id           and orderdetail.items_id = items.id    

@Test    public void func() throws IOException {        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        SqlSession session = sessionFactory.openSession();        UserMapper userMapper = session.getMapper(UserMapper.class);        List
    
      users = userMapper.getUserAndOrder();        for (User user : users) {            System.out.println(user);            for (Orders order : user.getOrdersList()) {                System.out.println(order);                for (OrderDetail orderDetail : order.getOrderDetails()) {                    System.out.println(orderDetail + ":" + orderDetail.getItems());                }                System.out.println("===============");            }        }    }
    

懒加载

OrdersMapper.xml

            
             
             
             
             
             
                select * from orders    

SqlMapConfig.xml

@Test    public void func() throws IOException {        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);        SqlSession session = sessionFactory.openSession();        OrdersMapper ordersMapper = session.getMapper(OrdersMapper.class);         List
    
      orders = ordersMapper.getOrderAndUserByLazyLoading();        for (Orders order : orders) {            System.out.println(order);            System.out.println(order.getUser());        }    }