mybatis--多对多查询
实体类
//多对多的关系映射:一个角色可以赋予多个用户 private List<User> users; public List<User> getUsers() { return users; } public void setUsers(List<User> users) { this.users = users; }
映射配置文件
<?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"> <mapper namespace="com.itheima.dao.IRoleDao"> <!--定义role表的ResultMap--> <resultMap id="roleMap" type="role"> <id property="roleId" column="rid"></id> <result property="roleName" column="role_name"></result> <result property="roleDesc" column="role_desc"></result> <collection property="users" ofType="user"> <id column="id" property="id"></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> </collection> </resultMap> <!--查询所有--> <select id="findAll" resultMap="roleMap"> select u.*,r.id as rid,r.role_name,r.role_desc from role r left outer join user_role ur on r.id = ur.rid left outer join user u on u.id = ur.uid </select> </mapper>
测试
@Test public void testFindAll(){ List<Role> roles = roleDao.findAll(); for(Role role : roles){ System.out.println("---每个角色的信息----"); System.out.println(role); System.out.println(role.getUsers()); } }