mybatis学习笔记三（实现关联数据的查询）

实现关联数据的查询

1 创建数据源

#创建表article

Drop TABLE IF EXISTS `article`;

Create TABLE `article` (

`id` int(11) NOT NULL auto_increment,

`userid` int(11) NOT NULL,

`title` varchar(100) NOT NULL,

`content` text NOT NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------

-- 添加几条测试数据

-- ----------------------------

Insert INTO `article` VALUES ('1', '1', 'test_title', 'test_content');

Insert INTO `article` VALUES ('2', '1', 'test_title_2', 'test_content_2');

Insert INTO `article` VALUES ('3', '1', 'test_title_3', 'test_content_3');

Insert INTO `article` VALUES ('4', '1', 'test_title_4', 'test_content_4');

2 实体

public class Article {

/* id */

private int id;

/* 作者 */

private User user;

/* 标题 */

private String title;

/* 内容 */

private String content;

getter/setter..

}

3 修改user.xml

<!--文章article -->

<resultMap id="resultUserArticleList" type="cn.yue.mybatis.model.Article">

<id property="id" column="aid" />

<result property="title" column="title" />

<result property="content" column="content" />

<association property="user" javaType="cn.yue.mybatis.model.User">

<id property="id" column="id" />

<result property="userName" column="userName" />

<result property="userAddress" column="userAddress" />

</association>

</resultMap>

<!-- 根据用户id查询论文 -->

<select id="getUserArticles" parameterType="int"

resultMap="resultUserArticleList">

select

user.id,user.userName,user.userAddress,article.id

aid,article.title,article.content from user,article

where

user.id=article.userid and user.id=#{id}

</select>

4 测试

/**

* 根据用户id查询文章

*

* @param id

*/

public static void getUserArticles(int userId) {

SqlSession session = sqlSessionFactory.openSession();

try {

IUserOperation userOperation = session.getMapper(IUserOperation.class);

List<Article> articles = userOperation.getUserArticles(userId);

for (Article article : articles) {

System.out.println(article.getTitle() + ":" + article.getContent() + ":作者是:" + article.getUser().getUserName() + ":地址:" + article.getUser().getUserAddress());

}

} finally {

session.close();

}

}

参考：http://blog.csdn.net/techbirds_bao/article/details/9233599/