mybatis学习(47):嵌套查询--一对一

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">
 <!-- 为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，这样就能够保证namespace的值是唯一的
 例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后缀)
  -->
 <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.pojoAuthor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.utilMybatisUtil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" />
             <!-- 配置数据库连接信息 -->
             <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>
         <!-- 注册userMapper.xml文件， 
          userMapper.xml位于me.gacl.mapping这个包下，所以resource写成me/gacl/mapping/userMapper.xml-->
          <mapper resource="com/geyao/mybatis/mapper/BlogMapper.xml"/>
           <mapper resource="com/geyao/mybatis/mapper/AuthorMapper.xml"/>
      </mappers>
 </configuration>
 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%n