mybatis学习(49):嵌套查询--一对多
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mybatis学习(49):嵌套查询--一对多
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數據庫表
數據庫叫blog_gp1701
author表
數據
blog表
數據
comment表
數據
post表
數據
目錄結構
jar包導入
先給對應的jar包導入
建立一個junit單元測試
配置文件
log4j.properties
### \u914D\u7F6E\u6839 ### log4j.rootLogger = debug,console ,fileAppender,dailyRollingFile,ROLLING_FILE,MAIL,DATABASE### \u8BBE\u7F6E\u8F93\u51FAsql\u7684\u7EA7\u522B\uFF0C\u5176\u4E2Dlogger\u540E\u9762\u7684\u5185\u5BB9\u5168\u90E8\u4E3Ajar\u5305\u4E2D\u6240\u5305\u542B\u7684\u5305\u540D ### log4j.logger.org.apache=dubug log4j.logger.java.sql.Connection=dubug log4j.logger.java.sql.Statement=dubug log4j.logger.java.sql.PreparedStatement=dubug log4j.logger.java.sql.ResultSet=dubug### \u914D\u7F6E\u8F93\u51FA\u5230\u63A7\u5236\u53F0 ### log4j.appender.console = org.apache.log4j.ConsoleAppender log4j.appender.console.Target = System.out log4j.appender.console.layout = org.apache.log4j.PatternLayout log4j.appender.console.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{1}:%L - %m%nmybatis-config.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <settings><setting name="useGeneratedKeys" value="true"/> </settings> <typeAliases><typeAlias type="com.geyao.mybatis.pojo.Blog" alias="Blog"/><typeAlias type="com.geyao.mybatis.pojo.Author" alias="Author"/><typeAlias type="com.geyao.mybatis.pojo.Comment" alias="Comment"/><typeAlias type="com.geyao.mybatis.pojo.Post" alias="Post"/> </typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC" /><!-- 配置數據庫連接信息 --><dataSource type="POOLED"><property name="driver" value="com.mysql.cj.jdbc.Driver" /><property name="url" value="jdbc:mysql://localhost:3306/blog_gp1701?serverTimezone=GMT%2B8" /><property name="username" value="root" /><property name="password" value="123" /></dataSource></environment></environments><mappers><!-- 注冊userMapper.xml文件， userMapper.xml位于me.gacl.mapping這個包下，所以resource寫成me/gacl/mapping/userMapper.xml--><mapper resource="com/geyao/mybatis/mapper/BlogMapper.xml"/><mapper resource="com/geyao/mybatis/mapper/AuthorMapper.xml"/><mapper resource="com/geyao/mybatis/mapper/PostMapper.xml"/><mapper resource="com/geyao/mybatis/mapper/CommentMapper.xml"/></mappers> </configuration>com.geyao.mybatis.mapper
AuthorMapper
package com.geyao.mybatis.mapper;import com.geyao.mybatis.pojo.Author; public interface AuthorMapper {Author selectAuthorById(Integer id); }BlogMapper
package com.geyao.mybatis.mapper;import java.util.List;import com.geyao.mybatis.pojo.Blog;public interface BlogMapper {Blog selectBlogById(Integer id);List<Blog> selectBlogList(); }Comment.Maoper
package com.geyao.mybatis.mapper;import java.util.List;import com.geyao.mybatis.pojo.Comment;public interface CommentMapper { List<Comment> selectCommentByPostId(Integer id); }PostMapper
package com.geyao.mybatis.mapper;import com.geyao.mybatis.pojo.Post;public interface PostMapper {Post selectPostById(Integer id); }AuthorMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- 為這個mapper指定一個唯一的namespace，namespace的值習慣上設置成包名+sql映射文件名，這樣就能夠保證namespace的值是唯一的 例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后綴)--> <mapper namespace="com.geyao.mybatis.mapper.AuthorMapper"><resultMap type="Author" id="authorResultMap"><id column="id" property="id" jdbcType="INTEGER"></id></resultMap><select id="selectAuthorById" parameterType="int" resultMap="authorResultMap">select * from author where id=#{id}</select> </mapper>BlogMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.geyao.mybatis.mapper.BlogMapper"><resultMap type="Blog" id="blogResultMap"><id column="id" property="id" jdbcType="INTEGER"></id> <association property="author" column="author" javaType="Author"select="com.geyao.mybatis.mapper.AuthorMapper.selectAuthorById"></association></resultMap><select id="selectBlogById" parameterType="int" resultMap="blogResultMap">select * from Blog where id=#{id}</select><select id="selectBlogList" resultMap="blogResultMap">select * from Blog </select> </mapper>CommentMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- 為這個mapper指定一個唯一的namespace，namespace的值習慣上設置成包名+sql映射文件名，這樣就能夠保證namespace的值是唯一的 例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后綴)--> <mapper namespace="com.geyao.mybatis.mapper.CommentMapper"><resultMap type="Comment" id="commentResultMap"><id column="id" property="id" jdbcType="INTEGER"></id></resultMap><select id="selectCommentByPostId" parameterType="int" resultMap="commentResultMap">select * from comment where post_id=#{postId}</select><select id="selectCommentById" parameterType="int" resultMap="commentResultMap">select * from comment where id=#{id}</select> </mapper>PostMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!-- 為這個mapper指定一個唯一的namespace，namespace的值習慣上設置成包名+sql映射文件名，這樣就能夠保證namespace的值是唯一的 例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后綴)--> <mapper namespace="com.geyao.mybatis.mapper.PostMapper"><resultMap type="Post" id="postResultMap"><id column="id" property="id" jdbcType="INTEGER"></id><collection property="commentList" column="id" javaType="ArrayList" ofType="Comment"select="com.geyao.mybatis.mapper.CommentMapper.selectCommentByPostId"></collection></resultMap><select id="selectPostById" parameterType="int" resultMap="postResultMap">select * from post where id=#{id}</select> </mapper>com.geyao.mybatis.pojo
Author
package com.geyao.mybatis.pojo;public class Author {private Integer id;private String username;private String password;private String email;private String bio;private String favouriteSection;private String nickname;private String realname;public Author() {super();}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public String getBio() {return bio;}public void setBio(String bio) {this.bio = bio;}public String getFavouriteSection() {return favouriteSection;}public void setFavouriteSection(String favouriteSection) {this.favouriteSection = favouriteSection;}public String getNickname() {return nickname;}public void setNickname(String nickname) {this.nickname = nickname;}public String getRealname() {return realname;}public void setRealname(String realname) {this.realname = realname;}public Author(Integer id, String username, String password, String email, String bio, String favouriteSection,String nickname, String realname) {super();this.id = id;this.username = username;this.password = password;this.email = email;this.bio = bio;this.favouriteSection = favouriteSection;this.nickname = nickname;this.realname = realname;}@Overridepublic String toString() {return "Author [id=" + id + ", username=" + username + ", password=" + password + ", email=" + email + ", bio="+ bio + ", favouriteSection=" + favouriteSection + ", nickname=" + nickname + ", realname=" + realname+ "]";}}Blog
package com.geyao.mybatis.pojo;import java.io.Serializable;public class Blog implements Serializable {private static final long serialVersionUID = 1L;private Integer id;private String title;private Author author;private String state;private boolean featured;private String style;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 Author getAuthor() {return author;}public void setAuthor(Author author) {this.author = author;}public String getState() {return state;}public void setState(String state) {this.state = state;}public boolean isFeatured() {return featured;}public void setFeatured(boolean featured) {this.featured = featured;}public String getStyle() {return style;}public void setStyle(String style) {this.style = style;}public static long getSerialversionuid() {return serialVersionUID;}@Overridepublic String toString() {return "Blog [id=" + id + ", title=" + title + ", author=" + author + ", state=" + state + ", featured="+ featured + ", style=" + style + "]\n";}}Comment
package com.geyao.mybatis.pojo;import java.util.Date;public class Comment {private Integer id;private String name;private String comment;private Date createOn;private Post post;private Author author;public Comment() {}public Comment(Integer id, String name, String comment, Date createOn, Post post, Author author) {super();this.id = id;this.name = name;this.comment = comment;this.createOn = createOn;this.post = post;this.author = author;}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;}public String getComment() {return comment;}public void setComment(String comment) {this.comment = comment;}public Date getCreateOn() {return createOn;}public void setCreateOn(Date createOn) {this.createOn = createOn;}public Post getPost() {return post;}public void setPost(Post post) {this.post = post;}public Author getAuthor() {return author;}public void setAuthor(Author author) {this.author = author;}@Overridepublic String toString() {return "Comment [id=" + id + ", name=" + name + ", comment=" + comment + ", createOn=" + createOn + ", post="+ post + ", author=" + author + "]";}}Post
package com.geyao.mybatis.pojo;import java.util.Date; import java.util.List;public class Post {private Integer id;private Author author;private Blog blog;private Date createOn;private String section;private String subject;private String draft;private String body;private Integer visit;private List<Comment> commentList;public Post(Integer id, Author author, Blog blog, Date createOn, String section, String subject, String draft,String body, Integer visit, List<Comment> commentList) {super();this.id = id;this.author = author;this.blog = blog;this.createOn = createOn;this.section = section;this.subject = subject;this.draft = draft;this.body = body;this.visit = visit;this.commentList = commentList;}public Post() {super();}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public Author getAuthor() {return author;}public void setAuthor(Author author) {this.author = author;}public Blog getBlog() {return blog;}public void setBlog(Blog blog) {this.blog = blog;}public Date getCreateOn() {return createOn;}public void setCreateOn(Date createOn) {this.createOn = createOn;}public String getSection() {return section;}public void setSection(String section) {this.section = section;}public String getSubject() {return subject;}public void setSubject(String subject) {this.subject = subject;}public String getDraft() {return draft;}public void setDraft(String draft) {this.draft = draft;}public String getBody() {return body;}public void setBody(String body) {this.body = body;}public Integer getVisit() {return visit;}public void setVisit(Integer visit) {this.visit = visit;}public List<Comment> getCommentList() {return commentList;}public void setCommentList(List<Comment> commentList) {this.commentList = commentList;}@Overridepublic String toString() {return "Post [id=" + id + ", author=" + author + ", blog=" + blog + ", createOn=" + createOn + ", section="+ section + ", subject=" + subject + ", draft=" + draft + ", body=" + body + ", visit=" + visit + "]";}}com.geyao.mybatis.util
MybatisUtil
package com.geyao.mybatis.util;import java.io.InputStream; import java.io.Reader;import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder;public class MyBatisUtil {private static SqlSessionFactory sqlSessionFactory =null;static {try {InputStream in = Resources.getResourceAsStream("mybatis-config.xml");sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}private MyBatisUtil() {}public static SqlSession getSqlSession() {return sqlSessionFactory.openSession();} }單元測試
com.geyao.mybatis.mapper
PostMannerTest
package com.geyao.mybatis.mapper;import org.apache.ibatis.session.SqlSession; import org.junit.Test;import com.geyao.mybatis.pojo.Blog; import com.geyao.mybatis.pojo.Post; import com.geyao.mybatis.util.MyBatisUtil;public class PostMapperTest {@Testpublic void testSelectPost() {SqlSession session =MyBatisUtil.getSqlSession();PostMapper postMapper =session.getMapper(PostMapper.class);Post post = postMapper.selectPostById(1);session.close();System.out.println(post);} }運行結果
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