mybatis返回HashMap结果类型与映射

 

<!-- 返回HashMap结果 类型-->
    <!-- 如果想返回JavaBean,只需将resultType设置为JavaBean的别名或全限定名 -->
    <!-- TypeAliasRegistry类初始化时注册了一些常用的别名，如果忘记了别名可以在这里面查看 -->
    <select id="selectBlogRetHashMap" parameterType="int" resultType="map">
        SELECT id AS "id", title AS "title", content AS "content" FROM Blog WHERE id = #{id}
    </select>

测试代码：

/**
     * 测试返回HashMap
     */
    @SuppressWarnings("unchecked")
    @Test
    public void testSelectBlogRetHashMap() {
        SqlSession session = sqlSessionFactory.openSession();
        HashMap<String,Object> blog = (HashMap<String,Object>) session.selectOne(
                "cn.enjoylife.BlogMapper.selectBlogRetHashMap", 15);
        session.close();
        System.out.println(blog.get("title"));
    }

 

ibatis高级映射：

表结构:

 

create table BLOG
(
  ID             NUMBER(20),
  TITLE          VARCHAR2(50),
  CONTENT        VARCHAR2(4000),
  BLOG_AUTHOR_ID NUMBER(20)
)
create table AUTHOR
(
  ID          NUMBER(20),
  AUTHOR_NAME VARCHAR2(50)
);
create table POSTS
(
  ID      NUMBER(20),
  SUBJECT VARCHAR2(50),
  BODY    VARCHAR2(4000),
  BLOG_ID NUMBER(20)
)

bean信息：

package cn.enjoylife.domain;
import java.util.List;
public class Blog {
    private Integer id;
    private String title;
    private String content;
    private Author author;

    private List<Post> posts/*=new ArrayList<Post>()*/;

    public List<Post> getPosts() {
        return posts;
    }
    public void setPosts(List<Post> posts) {
        this.posts = posts;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    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;
    }
    public Author getAuthor() {
        return author;
    }
    public void setAuthor(Author author) {
        this.author = author;
    }
    @Override
    public String toString() {
        return "Blog [content=" + content + ", id=" + id + ", title=" + title
                + "]";
    }
}

package cn.enjoylife.domain;
public class Author {
    private Integer id;
    private String name;
    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;
    }
    @Override
    public String toString() {
//      System.out.println("Author[id="+id+",name="+name+"]");
        return "Author[id="+id+",name="+name+"]";
    }

}

package cn.enjoylife.domain;
public class Post {
    private Integer id;
    private String subject;
    private String postContent;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getSubject() {
        return subject;
    }
    public void setSubject(String subject) {
        this.subject = subject;
    }
    public String getPostContent() {
        return postContent;
    }
    public void setPostContent(String postContent) {
        this.postContent = postContent;
    }
    @Override
    public String toString() {
        return "Post [postContent=" + postContent + ", id=" + id + ", subject=" + subject
                + "]";
    }


}

Blog.xmll配置:

<!-- 高级结果映射 -->
    <!--
         一对一关联 嵌套查询 应用select属性
         1)id="selectBlogAndRelatedAuthor" 中的 blog_author_id 对应到
         <association property="author" column="blog_author_id"/>中的column="blog_author_id"
         2)我们执行selectBlogAndRelatedAuthor 1次之后，所产生的每条记录都要再进行一个查询来获取author信息（N），
         这就是N+1问题，应该使用延迟加载的方式，否则这有可能产生致命的后果。
         3)对于一对一关联,我设置了
            <settings>
                <setting name="lazyLoadingEnabled" value="true"/>
            </settings>
          却没有对Author进行延迟加载，不知为何。。。
    -->
    <resultMap id="blogResult" type="Blog" >
        <association property="author" column="blog_author_id"
        javaType="Author" select="selectAuthor"  />
    </resultMap>
    <select id="selectBlogAndRelatedAuthor" parameterType="int" resultMap="blogResult" >
        SELECT id,title,content,blog_author_id FROM blog WHERE id = #{id}
    </select>
    <select id="selectAuthor" parameterType="int" resultType="Author">
        SELECT id,author_name as "name" FROM author WHERE id = #{id}
    </select>
    <!--
         一对一关联 嵌套结果
    -->
    <resultMap id="blogResult2" type="Blog">
        <id property="id" column="id" />
        <result property="title" column="title"/>
        <association property="author" column="blog_author_id"
            javaType="Author">
            <id property="id" column="author_id"/>
            <result property="name" column="author_name"/>
        </association>
    </resultMap>
    <select id="selectBlogAndRelatedAuthor2" parameterType="int" resultMap="blogResult2" >
        SELECT t.ID, t.TITLE, t.CONTENT, a.id as "author_id", a.author_name
          FROM blog t
         INNER JOIN author a ON t.BLOG_AUTHOR_ID = a.ID
                            AND t.ID = #{id}
    </select>

    <!--
         一对多关联  嵌套查询，应用select属性
        <collection property="posts" column="id" javaType="ArrayList" ofType="Post"
            select="selectPosts"/>中的column指得是Post所对应表中的引用的主表中的主键id,
        注意：这个column指的是主表（Blog)中的id,我在这犯了个错，写为Post所对应表中的外键id,这是不对的，
                       应为所引用主表的主键id。
        property="posts" javaType="ArrayList" ofType="Post" 指属性posts为元素为Post的ArrayList类型

        同样没有进行延迟加载，不知为何。。。
    -->
    <resultMap type="Blog" id="blogResult3" >
        <id property="id" column="id"/>
        <result property="title" column="title"/>
        <result property="content" column="content"/>
        <collection property="posts" column="id" javaType="ArrayList" ofType="Post"
            select="selectPosts"/>
    </resultMap>
    <select id="selectBlogAndRelatedPosts" parameterType="int" resultMap="blogResult3" >
        SELECT id, title, content FROM blog WHERE id = #{id}
    </select>
    <select id="selectPosts" parameterType="int" resultType="Post" >
        SELECT p.id,p.subject,p.body as "postContent" FROM posts p WHERE p.blog_id =#{id}
    </select>

    <!--
         一对多关联  嵌套结果,在使用这种方式时，sql语句应该使用别名以保证不重复，如果不这样，可能
        出现结果不正确的现象，比如以下的post_id别名
    -->
    <resultMap type="Blog" id="blogResultVersion" >
        <id property="id" column="id" />
        <result property="title" column="title"/>
        <result property="content" column="content"/>
        <collection property="posts" javaType="ArrayList" ofType="Post" column="id">
            <id property="id" column="post_id"/>
            <result property="subject" column="subject"/>
            <result property="postContent" column="postContent"/>
        </collection>
    </resultMap>
    <select id="selectBlogAndRelatedPosts2" parameterType="int"  resultMap="blogResultVersion">
        SELECT t.id, t.title, t.content, p.id as "post_id", p.subject, p.BODY as "postContent"
          FROM blog t
         left outer JOIN posts p ON t.id = p.blog_id
         WHERE t.ID = #{id}
    </select>

测试代码：

/**
     * 测试一对一关联 嵌套查询
     */
    @Test
    public void testSelectBlogAndRelatedAuthor() {
        SqlSession session = sqlSessionFactory.openSession();
        Blog blog = (Blog) session.selectOne(
                "cn.enjoylife.BlogMapper.selectBlogAndRelatedAuthor", 15);
        System.out.println(blog.toString());
        session.close();
        System.out.println(blog.getAuthor());
    }

    /**
     * 测试一对一关联 嵌套结果
     */
    @Test
    public void testSelectBlogAndRelatedAuthor2() {
        SqlSession session = sqlSessionFactory.openSession();
        Blog blog = (Blog) session.selectOne(
                "cn.enjoylife.BlogMapper.selectBlogAndRelatedAuthor2", 15);
        session.close();
        System.out.println(blog.toString());
        System.out.println(blog.getAuthor());
    }

    /**
     * 测试一对多关联 嵌套查询
     */
    @Test
    public void testSelectBlogAndRelatedPosts() throws Exception {
        SqlSession session = sqlSessionFactory.openSession();
        Blog blog = (Blog) session.selectOne(
                "cn.enjoylife.BlogMapper.selectBlogAndRelatedPosts", 15);
        System.out.println(blog.toString());
        session.close();
        System.out.println(blog.getPosts());
    }

    /**
     * 测试一对多关联 嵌套结果
     */
    @Test
    public void testSelectBlogAndRelatedPosts2() throws Exception {
        SqlSession session = sqlSessionFactory.openSession();
        Blog blog = (Blog) session.selectOne(
                "cn.enjoylife.BlogMapper.selectBlogAndRelatedPosts2", 15);
        session.close();
        System.out.println(blog.toString());
        System.out.println(blog.getPosts());
    }