MyBatis一对多问题记录

MyBatis一对多。

需要cglig.jar和asm.jar的支持。

有三张表，通过User表查询User_Role中核角色的对应关系，然后通过这个对应关系查询到用户所属角色。

上代码：

user.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.yrsoft.dao.UserDao"><resultMap type="com.yrsoft.entity.User" id="User" ><id column="id" property="id"/><result column="username" property="username"/><result column="password" property="password"/><result column="isDelete" property="isDelete"/><result column="createDate" property="createDate"/><collection property="userRoles" ofType="com.yrsoft.dao.UserRoleDao.UserRole" select="com.yrsoft.dao.UserRoleDao.findByUserId" column="id"></collection></resultMap><select id="findUserByUserName" resultMap="User">select * from t_user where username = #{username}</select><select id="findAll" resultMap="User">select * from t_user</select></mapper>

userRole.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.yrsoft.dao.UserRoleDao"><resultMap type="com.yrsoft.entity.UserRole" id="UserRole"><id column="id" property="id"/><result column="user" property="userId" javaType="int" jdbcType="INTEGER"/><result column="role" property="roleId" javaType="int" jdbcType="INTEGER"/><association property="role" column="role" javaType="com.yrsoft.entity.Role" select="com.yrsoft.dao.RoleDao.findById"/> </resultMap><select id="findById" resultMap="UserRole">select * from t_user_role where id = #{id}</select><select id="findAll" resultMap="UserRole">select * from t_user_role</select><select id="findByUserId" parameterType="int" resultMap="UserRole">select * from t_user_role where user=#{id}</select></mapper>

role.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.yrsoft.dao.RoleDao"><resultMap type="com.yrsoft.entity.Role" id="Role"><id column="id" property="id"/><result column="name" property="name"/><result column="description" property="description"/></resultMap><select id="findById" resultMap="Role">select * from t_role where id = #{id}</select><select id="findAll" resultMap="Role">select * from t_user_role</select></mapper>

User.java

package com.yrsoft.entity;import java.sql.Timestamp;import java.util.List;/*** * 用户表 */public class User {Integer id;/** 用户名 **/String username;/** 密码 **/String password;/** 是否删除 **/Integer isDelete;/** 创建时间 **/Timestamp createDate;// 多对多用户权限表List<UserRole> userRoles;public Integer getId() {return id;}public void setId(Integer 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 Integer getIsDelete() {return isDelete;}public void setIsDelete(Integer isDelete) {this.isDelete = isDelete;}public Timestamp getCreateDate() {return createDate;}public void setCreateDate(Timestamp createDate) {this.createDate = createDate;}public List<UserRole> getUserRoles() {return userRoles;}public void setUserRoles(List<UserRole> userRoles) {this.userRoles = userRoles;}@Overridepublic String toString() {return "\"User\":{\"id\":" + id + ",\"username\":" + username + ",\"password\":"+ password + ",\"isDelete\":" + isDelete + ",\"createDate\":"+ createDate + ",\"userRoles\":" + userRoles + "}";}}

UserRole.java

package com.yrsoft.entity;/*** * 用户角色表 */public class UserRole {Integer id;int userId;int roleId;/*User user;*/Role role;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public int getUserId() {return userId;}public void setUserId(int userId) {this.userId = userId;}public int getRoleId() {return roleId;}public void setRoleId(int roleId) {this.roleId = roleId;}public Role getRole() {return role;}public void setRole(Role role) {this.role = role;}@Overridepublic String toString() {return "\"UserRole\":{\"id\":" + id + ",\"userId\":" + userId + ",\"roleId\":"+ roleId + ",\"Role\":"+role+"}";}}

Role.java

package com.yrsoft.entity;/**** * 角色表 */public class Role {Integer id;/** 角色名 **/String name;/** 角色说明 **/String description;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}@Overridepublic String toString() {return "\"Role\":{\"id\":" + id + ",\"name\":" + name + ",\"description\":"+ description + "}";}}

关键点：

一：一对一使用<association>标签，一对多直接使用<collection>标签
二：association标签中的column为要传进去的列名，是数据库中的列名，不是bean中的属性名。collection中的column同理

三：collection中，一定要写ofType属性，告诉系统你这个集合的泛型，有点像resultMap

参考文章：孤傲苍狼的博客