ibatis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()); }