#千锋逆战# Mybatis多表联合

Mybatis多表联合查找

1. 加入依赖

   • 加入mybatis核心依赖,junit测试,mysql依赖

   • 
         
             junit
             junit
             4.12
         
     
         
             mysql
             mysql-connector-java
             5.1.47
         
     
         
             org.mybatis
             mybatis
             3.4.6
         
     

2. XML配置

   • resources目录下新建Mybatis.xml文件

   • 导入db.properties资源文件,如下

     driver=com.mysql.jdbc.Driver
     url=jdbc:mysql://localhost:3307/shop_mybatis
     username=root
     password=970809
     

   • 设置settings,加入自动日志

   • 设置typeAliases,设置别名包,此包下的引用可直接写类名,忽略大小写

   • 设置连接池属性POOLED

   • 在mappers标签下设置对应的映射文件路径

3. OrderMapper.xml配置例举

   • namespace和id组合唯一,可自定义

   • 使用select标签进行查询操作,其他操作分别为update,insert,delete

   • 使用resultMap进行联合查询

   • resultMap标签下 如果对应pojo内的属性名(property)和数据库表中的列名相同,可省略不写result标签

   • 使用association标签进行对一的表结构联合查询,使用Collection标签进行对多的表结构联合查询

   • 
     
     
         
             select * from orders where oid = #{oid}
       
         
         
     
     
     
     
     
             
             
     
            
             
         
     
     

4. UserMapper.xml

   • 
     
     
         
         select * from users where uid = #{uid}
       
     
     
     

5. DetailMapper.xml

   • 
     
     
         
             select * from details where did = #{did}
       
     
     
         
     
     
     
             
         
     
     
     

6. ProductMapper.xml

   • 
     
     
         
         select * from products where pid = #{pid}
       
     
         
     
     
     
     
     
     
             
         
     
     
     

7. TypeMapper.xml

   • 
     
     
         
         select * from types where tid = #{tid}
       
     
     
     

8. 测试类

   • 使用junit的@Before注解,setUp在所有方法运行前运行

   • 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 pojo.Order;
     
     import java.io.IOException;
     
     public class TestOrders {
         private SqlSessionFactory sf = null;
         private SqlSession session = null;
     
         @Before
         public void setUp() {
             try {
                 sf = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("Mybatis.xml"));
                 session = sf.openSession();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
     
         @After
         public void tearDown() {
             if (session != null) {
                 session.close();
                 session = null;
             }
         }
     
         @Test
         public void testGetOrderByOid() {
             Order order = session.selectOne("pojo.OrderMapper.getOrderByOid",1);
             System.out.println(order);
         }
     }