Xhtml代码
1. <!-- 返回HashMap结果 类型-->
2. <!-- 如果想返回JavaBean,只需将resultType设置为JavaBean的别名或全限定名 -->
3. <!-- 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 -->
4. <select id="selectBlogRetHashMap" parameterType="int" resultType="map">
5. id
6. </select> 测试代码：
Java代码
1. /**
2. * 测试返回HashMap
3. */
4. @SuppressWarnings("unchecked")
5. @Test
6. public void
7. SqlSession session = sqlSessionFactory.openSession();
8. HashMap<String,Object> blog = (HashMap<String,Object>) session.selectOne(
9. "cn.enjoylife.BlogMapper.selectBlogRetHashMap", 15);
10. session.close();
11. "title"));
12. }
ibatis高级映射：
表结构:
Java代码
1. create table BLOG
2. (
3. 20),
4. 50),
5. 4000),
6. 20)
7. )
8. create table AUTHOR
9. (
10. 20),
11. 50)
12. );
13. create table POSTS
14. (
15. 20),
16. 50),
17. 4000),
18. 20)
19. )
bean信息：
Java代码
1. package
2. import
3. public class
4. private
5. private
6. private
7. private
8.
9. private List<Post> posts/*=new ArrayList<Post>()*/;
10.
11. public
12. return
13. }
14. public void
15. this.posts = posts;
16. }
17. public
18. return
19. }
20. public void
21. this.id = id;
22. }
23. public
24. return
25. }
26. public void
27. this.title = title;
28. }
29. public
30. return
31. }
32. public void
33. this.content = content;
34. }
35. public
36. return
37. }
38. public void
39. this.author = author;
40. }
41. @Override
42. public
43. return "Blog [content=" + content + ", id=" + id + ", title="
44. "]";
45. }
46. }
Java代码
1. package
2. public class
3. private
4. private
5. public
6. return
7. }
8. public void
9. this.id = id;
10. }
11. public
12. return
13. }
14. public void
15. this.name = name;
16. }
17. @Override
18. public
19. // System.out.println("Author[id="+id+",name="+name+"]");
20. return "Author[id="+id+",name="+name+"]";
21. }
22.
23. }
Java代码
1. package
2. public class
3. private
4. private
5. private
6. public
7. return
8. }
9. public void
10. this.id = id;
11. }
12. public
13. return
14. }
15. public void
16. this.subject = subject;
17. }
18. public
19. return
20. }
21. public void
22. this.postContent = postContent;
23. }
24. @Override
25. public
26. return "Post [postContent=" + postContent + ", id=" + id + ", subject="
27. "]";
28. }
29.
30.
31. } Blog.xmll配置:
Xhtml代码
1. <!-- 高级结果映射 -->
2. <!--
3. 一对一关联 嵌套查询 应用select属性
4. id="selectBlogAndRelatedAuthor"
5. <association property="author" column="blog_author_id"/>中的column="blog_author_id"
6. 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），
7. 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。
8. 3)对于一对一关联,我设置了
9. <settings>
10. <setting name="lazyLoadingEnabled" value="true"/>
11. </settings>
12. 却没有对Author进行延迟加载，不知为何。。。
13. >
14. <resultMap id="blogResult" type="Blog" >
15. <association property="author" column="blog_author_id"
16. javaType="Author" select="selectAuthor" />
17. </resultMap>
18. <select id="selectBlogAndRelatedAuthor" parameterType="int" resultMap="blogResult" >
19. id
20. </select>
21. <select id="selectAuthor" parameterType="int" resultType="Author">
22. id
23. </select>
24. <!--
25. 一对一关联 嵌套结果
26. -->
27. <resultMap id="blogResult2" type="Blog">
28. <id property="id" column="id" />
29. <result property="title" column="title"/>
30. <association property="author" column="blog_author_id"
31. javaType="Author">
32. <id property="id" column="author_id"/>
33. <result property="name" column="author_name"/>
34. </association>
35. </resultMap>
36. <select id="selectBlogAndRelatedAuthor2" parameterType="int" resultMap="blogResult2" >
37. SELECT t.ID, t.TITLE, t.CONTENT, a.id as "author_id", a.author_name
38. FROM blog t
39. t.BLOG_AUTHOR_ID = a.ID
40. t.ID
41. </select>
42.
43. <!--
44. 一对多关联 嵌套查询，应用select属性
45. <collection property="posts" column="id" javaType="ArrayList" ofType="Post"
46. 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,
47. 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，
48. 应为所引用主表的主键id。
49. property="posts" javaType="ArrayList" ofType="Post"
50.
51. 同样没有进行延迟加载，不知为何。。。
52. >
53. <resultMap type="Blog" id="blogResult3" >
54. <id property="id" column="id"/>
55. <result property="title" column="title"/>
56. <result property="content" column="content"/>
57. <collection property="posts" column="id" javaType="ArrayList" ofType="Post"
58. select="selectPosts"/>
59. </resultMap>
60. <select id="selectBlogAndRelatedPosts" parameterType="int" resultMap="blogResult3" >
61. id
62. </select>
63. <select id="selectPosts" parameterType="int" resultType="Post" >
64. p.blog_id
65. </select>
66.
67. <!--
68. 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
69. 出现结果不正确的现象，比如以下的post_id别名
70. >
71. <resultMap type="Blog" id="blogResultVersion" >
72. <id property="id" column="id" />
73. <result property="title" column="title"/>
74. <result property="content" column="content"/>
75. <collection property="posts" javaType="ArrayList" ofType="Post" column="id">
76. <id property="id" column="post_id"/>
77. <result property="subject" column="subject"/>
78. <result property="postContent" column="postContent"/>
79. </collection>
80. </resultMap>
81. <select id="selectBlogAndRelatedPosts2" parameterType="int" resultMap="blogResultVersion">
82. SELECT t.id, t.title, t.content, p.id as "post_id", p.subject, p.BODY as "postContent"
83. FROM blog t
84. t.id = p.blog_id
85. t.ID
86. </select> 测试代码：
Java代码
1. /**
2. * 测试一对一关联 嵌套查询
3. */
4. @Test
5. public void
6. SqlSession session = sqlSessionFactory.openSession();
7. Blog blog = (Blog) session.selectOne(
8. "cn.enjoylife.BlogMapper.selectBlogAndRelatedAuthor", 15);
9. System.out.println(blog.toString());
10. session.close();
11. System.out.println(blog.getAuthor());
12. }
13.
14. /**
15. * 测试一对一关联 嵌套结果
16. */
17. @Test
18. public void
19. SqlSession session = sqlSessionFactory.openSession();
20. Blog blog = (Blog) session.selectOne(
21. "cn.enjoylife.BlogMapper.selectBlogAndRelatedAuthor2", 15);
22. session.close();
23. System.out.println(blog.toString());
24. System.out.println(blog.getAuthor());
25. }
26.
27. /**
28. * 测试一对多关联 嵌套查询
29. */
30. @Test
31. public void testSelectBlogAndRelatedPosts() throws
32. SqlSession session = sqlSessionFactory.openSession();
33. Blog blog = (Blog) session.selectOne(
34. "cn.enjoylife.BlogMapper.selectBlogAndRelatedPosts", 15);
35. System.out.println(blog.toString());
36. session.close();
37. System.out.println(blog.getPosts());
38. }
39.
40. /**
41. * 测试一对多关联 嵌套结果
42. */
43. @Test
44. public void testSelectBlogAndRelatedPosts2() throws
45. SqlSession session = sqlSessionFactory.openSession();
46. Blog blog = (Blog) session.selectOne(
47. "cn.enjoylife.BlogMapper.selectBlogAndRelatedPosts2", 15);
48. session.close();
49. System.out.println(blog.toString());
50. System.out.println(blog.getPosts());
51. }
