resultMap中两张表id字段相同，数据查询异常解决

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最近，在学习MyBatis 关联数据查询时，遇到了问题。

User表在本例子中存储文章作者的相关信息。User表的详细设计如下：

Article表存储了文章的相关内容。Article表的详细设计如下：

对应的实体类：

package com.test.mybatis.pojo;public class User {private int id;private String name;private int age;private String address;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public int getId() {return id;}public void setId(int id) {this.id = id;}}

package com.test.mybatis.pojo;public class Article {private int id;private User user;private String title;private String content;public int getId() {return id;}public void setId(int id) {this.id = id;}public User getUser() {return user;}public void setUser(User user) {this.user = user;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}}

需要注意的是，Article持有的是User的引用，而不是userid。

MyBatis配置如下：

<resultMap type="Article" id="userArticleList"><id column="id" property="id"/><result column="title" property="title"/><result column="content" property="content"/><association property="user" javaType="User"><id column="id" property="id" /><result column="name" property="name"/><result column="age" property="age"/><result column="address" property="address"/></association>
</resultMap>
<select id="queryArticlesByUser" parameterType="int" resultMap="userArticleList">select user.id, user.name, user.age, user.address, article.id, article.title, article.content from user, article where user.id = article.userid and user.id = #{id}
</select>

在Test中，传递User的id为1，只能查询到一条数据，而直接在命令行执行SQL语句，却能够查询到四条数据。

两张表中的id字段名相同，导致无法正常映射。解决办法是为列起别名。

<resultMap type="Article" id="userArticleList"><id column="id" property="id"/><result column="title" property="title"/><result column="content" property="content"/><association property="user" javaType="User"><!-- 别名uid --><id column="uid" property="id" /><result column="name" property="name"/><result column="age" property="age"/><result column="address" property="address"/></association>
</resultMap>
<select id="queryArticlesByUser" parameterType="int" resultMap="userArticleList">select user.id uid, user.name, user.age, user.address, article.id, article.title, article.content from user, article where user.id = article.userid and user.id = #{id}
</select>

这样便能正确查到四条数据。