mybatis学习(47):嵌套查询--一对一

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我是靠谱客的博主顺利小丸子，最近开发中收集的这篇文章主要介绍mybatis学习(47):嵌套查询--一对一，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

数据库

目录结构

映入jar包和junit单元测试

com.geyao.mybatis.mapper

AuthorMapper类

package com.geyao.mybatis.mapper;

import com.geyao.mybatis.pojo.Author;
public interface AuthorMapper {
Author selectAuthorById(Integer id);
}
BlogMapper类

package com.geyao.mybatis.mapper;

import com.geyao.mybatis.pojo.Blog;

public interface BlogMapper {
Blog selectBlogById(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">

<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>
</mapper>
com.geyao.mybatis.pojo

Author类

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;
   }
   @Override
   public String toString() {
       return "Author [id=" + id + ", username=" + username + ", password=" + password + ", email=" + email + ", bio="
               + bio + ", favouriteSection=" + favouriteSection + ", nickname=" + nickname + ", realname=" + realname
               + "]";
   }



}
Blog类

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;
   }
   @Override
   public String toString() {
       return "Blog [id=" + id + ", title=" + title + ", author=" + author + ", state=" + state + ", featured="
               + featured + ", style=" + style + "]";
   }




}
com.geyao.mybatis.util

MybatisUtil类

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 block
           e.printStackTrace();
       }
   }
   private MyBatisUtil() {}

   public static SqlSession getSqlSession() {
       return sqlSessionFactory.openSession();
   }
}
com.geyao.mybatis.mapper测试类

BlogMapperTest

package com.geyao.mybatis.mapper;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import com.geyao.mybatis.pojo.Author;
import com.geyao.mybatis.pojo.Blog;
import com.geyao.mybatis.util.MyBatisUtil;

public class BlogMapperTest {
   @Test
   public void testSelectBlog() {
       SqlSession session =MyBatisUtil.getSqlSession();
       BlogMapper blogMapper =session.getMapper(BlogMapper.class);

       Blog blog = blogMapper.selectBlogById(1);
       session.close();
       System.out.println(blog);
   }


}

mybatis-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"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />

<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>

<mapper resource="com/geyao/mybatis/mapper/BlogMapper.xml"/>
<mapper resource="com/geyao/mybatis/mapper/AuthorMapper.xml"/>
</mappers>
</configuration>
log4j.properties

### u914Du7F6Eu6839 ###
log4j.rootLogger = debug,console ,fileAppender,dailyRollingFile,ROLLING_FILE,MAIL,DATABASE

### u8BBEu7F6Eu8F93u51FAsqlu7684u7EA7u522BuFF0Cu5176u4E2Dloggeru540Eu9762u7684u5185u5BB9u5168u90E8u4E3Ajaru5305u4E2Du6240u5305u542Bu7684u5305u540D ###
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

### u914Du7F6Eu8F93u51FAu5230u63A7u5236u53F0 ###
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%n
运行结果