<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.32</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
</dependencies>
1.1 一对一查询
5. 配置OrderMapper.xml
<mapper namespace="com.itheima.mapper.OrderMapper">
<resultMap id="orderMap" type="com.itheima.domain.Order">
<result column="uid" property="user.id">
</result> <result column="username" property="user.username"></result>
<result column="password" property="user.password"></result>
<result column="birthday" property="user.birthday"></result>
</resultMap> <select id="findAll" resultMap="orderMap">
select * from orders o,user u where o.uid=u.id </select>
</mapper>
6. 测试结果
OrderMapper mapper = sqlSession.getMapper(OrderMapper.class); List<Order> all = mapper.findAll(); for(Order order : all){ System.out.println(order); }
4. 创建UserMapper接口
public interface UserMapper { List<User> findAll(); }
5. 配置UserMapper.xml
<mapper namespace="com.itheima.mapper.UserMapper">
<resultMap id="userMap" type="com.itheima.domain.User">
<result column="id" property="id"></result>
<result column="username" property="username"></result>
<result column="password" property="password"></result>
<result column="birthday" property="birthday"></result>
<collection property="orderList" ofType="com.itheima.domain.Order">
<result column="oid" property="id"></result>
<result column="ordertime" property="ordertime"></result>
<result column="total" property="total"></result>
</collection>
</resultMap>
<select id="findAll" resultMap="userMap">
select *,o.id oid from user u left join orders o on u.id=o.uid
</select>
</mapper>
一对多查询
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAll();
for(User user : all){
System.out.println(user.getUsername());
List<Order> orderList = user.getOrderList();
for(Order order : orderList){ System.out.println(order);
}
System.out.println("----------------------------------"); }
4. 添加UserMapper接口方法
List<User> findAllUserAndRole();
配置UserMapper.xml
<resultMap id="userRoleMap" type="com.itheima.domain.User">
<result column="id" property="id"></result> <result column="username" property="username"></result> <result column="password" property="password"></result>
<result column="birthday" property="birthday"></result>
<collection property="roleList" ofType="com.itheima.domain.Role">
<result column="rid" property="id"></result>
<result column="rolename" property="rolename"></result>
</collection>
</resultMap>
<select id="findAllUserAndRole" resultMap="userRoleMap">
select u.*,r.*,r.id rid from user u left join user_role ur on u.id=ur.user_id inner join role r on ur.role_id=r.id
</select>
6. 测试结果
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAllUserAndRole();
for(User user : all){
System.out.println(user.getUsername());
List<Role> roleList = user.getRoleList();
for(Role role : roleList){
System.out.println(role); }
System.out.println("----------------------------------");
}
