mybatis返回HashMap结果类型与映射
Xhtml代码
[*]<!-- 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：Java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:
Java代码
[*]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：Java代码
[*]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 + ", id=" + id + ", title=" + title
[*] + "]";
[*] }
[*]}
Java代码
[*]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");
[*] return "Author+id+",name="+name+"]";
[*] }
[*]
[*]}
Java代码
[*]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 + ", id=" + id + ", subject=" + subject
[*] + "]";
[*] }
[*]
[*]
[*]}
Blog.xmll配置:Xhtml代码
[*]<!-- 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：Java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());
[*] }
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