MyBatis中一对多的注解式开发

最新推荐文章于 2025-05-17 17:53:10 发布

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本文详细介绍使用MyBatis框架与MySQL数据库进行项目开发的过程，包括Maven项目搭建、依赖引入、实体类创建、Mapper接口定义及单元测试，实现一对多关系的数据查询。

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前言：本项目是使用idea进行开发，数据库使用的是Mysql。

其中，一对多的关系是Author--------Book

Author

Book

1.搭建一个maven项目

2.引入mybatis需要的依赖
习惯性建立java、resources、test等文件夹，建立文件夹的时候注意标记文件夹的用途（不然编译器无法识别，无法编译代码）

pom.xml(注意要将实体包下面的xml文件设置可编译)

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>MyBatis_Joy_03</groupId>
  <artifactId>MyBatis_Joy_03</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>MyBatis_Joy_03 Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.6</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.44</version>
    </dependency>
    <!-- **********************  日志配置  ********************** -->
    <!--记得修改mybatis.cfg.xml添加如下内容-->
    <!--<setting name="logImpl" value="LOG4J2"/>-->
    <!--核心log4j2jar包-->
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-core</artifactId>
      <version>2.9.1</version>
    </dependency>
    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-api</artifactId>
      <version>2.9.1</version>
    </dependency>
    <!--web工程需要包含log4j-web，非web工程不需要
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-web</artifactId>
        <version>2.9.1</version>
    </dependency>-->
  </dependencies>

  <build>
    <finalName>MyBatis_Joy_03</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

3.项目模块图

3.在resources目录下新建mybatis的核心配置文件mybatis.xml
mybatis.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>
    <!--日志配置文件-->
    <settings>
        <setting name="logImpl" value="LOG4J2"/>
        <setting name="autoMappingBehavior" value="FULL"/>
    </settings>


    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test?useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123"/>
            </dataSource>
        </environment>
    </environments>

    <!--配置实体映射关系-->
    <mappers>
        <mapper class="com.joy.mapper.AuthorMapper"></mapper>
        <mapper class="com.joy.mapper.BookMapper"></mapper>
    </mappers>
</configuration>

4.建立与数据库对应的实体包

Author.java

package com.joy.model;

import java.util.List;

public class Author {
    private int aid;
    private String aname;
    private List<Book> books;

    public Author() {
    }

    public Author(int aid, String aname, List<Book> books) {
        this.aid = aid;
        this.aname = aname;
        this.books = books;
    }

    public int getAid() {
        return aid;
    }

    public void setAid(int aid) {
        this.aid = aid;
    }

    public String getAname() {
        return aname;
    }

    public void setAname(String aname) {
        this.aname = aname;
    }

    public List<Book> getBooks() {
        return books;
    }

    public void setBooks(List<Book> books) {
        this.books = books;
    }

    @Override
    public String toString() {
        return "Author{" +
                "aid=" + aid +
                ", aname='" + aname + '\'' +
                ", books=" + books +
                '}';
    }
}

Book.java

package com.joy.model;

public class Book {
    private Integer bid;
    private String bname;
    private Author author;

    public Book() {
    }

    public Book(Integer bid, String bname, Author author) {
        this.bid = bid;
        this.bname = bname;
        this.author = author;
    }

    public Integer getBid() {
        return bid;
    }

    public void setBid(Integer bid) {
        this.bid = bid;
    }

    public String getBname() {
        return bname;
    }

    public void setBname(String bname) {
        this.bname = bname;
    }

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }

    @Override
    public String toString() {
        return "Book{" +
                "bid=" + bid +
                ", bname='" + bname + '\'' +
                ", author=" + author +
                '}';
    }
}

5.建立Mapper包，在包里建接口

AuthorMapper.java

package com.joy.mapper;

import com.joy.model.Author;
import org.apache.ibatis.annotations.Many;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

public interface AuthorMapper {
    //根据aid查询作者及其作品
    @Select("select * from author where aid=#{aid}")
    @Results({
            @Result(property = "aid",column = "aid",id = true),
            @Result(property = "books",column = "aid",many = @Many(select = "com.joy.mapper.BookMapper.findBookByAid"))
    })
    public Author findAuthorAndBookByAid(int aid);

    //根据bid其作者
    @Select("select * from author where aid=#{aid}")
    public Author findAuthorByAid(int aid);
}

BookMapper

package com.joy.mapper;

import com.joy.model.Book;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;

public interface BookMapper {
    //根据aid查询作品
    @Select("select * from book where aid=#{aid}")
    public Book findBookByAid(int aid);

    //根据bid查询作品及其作者
    @Select("select * from book where bid=#{bid}")
    @Results({
            @Result(property = "bid",column = "bid",id = true),
            @Result(property = "author",column = "aid",one = @One(select ="com.joy.mapper.AuthorMapper.findAuthorByAid"))
    })
    public Book findBookAndAuthorByBid(int bid);
}

6.在test文件夹下新建com.joy.test文件夹，并且新建单元测试类AuthorMapperTest.java

package com.joy.test;

import com.joy.mapper.AuthorMapper;
import com.joy.mapper.BookMapper;
import com.joy.model.Author;
import com.joy.model.Book;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.*;

public class AuthorMapperTest {

    private SqlSession sqlSession;

    @Before
    public void before(){
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(this.getClass().getClassLoader().getResourceAsStream("mybatis.xml"));
        sqlSession = sqlSessionFactory.openSession();
    }

    @Test
    public void test(){
        AuthorMapper authorMapper= sqlSession.getMapper(AuthorMapper.class);
        //根据aid查询作者及其作品
//        Author author= authorMapper.findAuthorAndBookByAid(1);
//        System.out.println(author);

        //根据bid查询作品及其作者
        BookMapper bookMapper=sqlSession.getMapper(BookMapper.class);
        Book book=  bookMapper.findBookAndAuthorByBid(1);
        System.out.println(book);
    }

}

7.取消注释，运行测试类即可

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