使用Mybatis实现多表多对多保存实例(含代码及解释)

多对多保存实例(保存学生)

项目目录结构(maven):

多对多保存学生灵魂之处解析:

StudentMapper.xml

不保存主键的运行结果:

新增学生的id为0,tea_id应该是正常的,只是因为我之前代码写错了,主要看学生id会为0;

(所有表id都设置了自动递增)

创建表t_stu:

创建表t_teacher:

 

创建关系表t_stu_tea:

在Maven配置文件pom.xml中添加所需要的依赖:

<?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>com.xiongluoluo</groupId>
    <artifactId>manytomany</artifactId>
    <version>1.0.0</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.8</version>
            <scope>provided</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/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
        </dependency>

        <!--日志包-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.25</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.25</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

</project>

创建实体类Student:

package com.xiongluoluo.bean;

import lombok.*;

import java.util.List;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
@Getter
@Setter
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Student {
    private int id;
    private String name;
    private List<Teacher> teacherList;
    /*这里new不new对象都行*/
}

 

创建实体类Teacher:

package com.xiongluoluo.bean;

import lombok.*;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class Teacher {
    private int id;
    private String name;
}

 

创建mybatis配置文件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>
    <properties resource="db.properties"/>
    <!--这里用的是resource属性,导入外部properties文件-->

    <typeAliases>
        <package name="com.xiongluoluo.bean"/>
    </typeAliases>
    
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driverClassName}"/>
                <!--这里是driver-->
                <!--driverClassName是properties文件中的变量,通过${}取其对应的支持-->
                <!--下面同理-->
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/xiongluoluo/mapper/StudentMapper.xml"/>
        <!--这里是斜线(因为是目录),不是点,不是点,不是点,你能不能不要在一个错误上躺平,每天忘提交事务,每天写...,唉-->
        <!--Mybatis的配置文件,也就是这个文件,是程序的入口.我们配置的mapper文件如果不在这里注册
        那么程序是读不到的.所以一定别忘记在这里添加.
        这里用的也是resource属性,引入外部的mapper.xml属性-->
    </mappers>
</configuration>

 

db.properties文件:

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///mydb1228
username=root
password=1234

log4j.properties文件:

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# MyBatis logging configuration...
log4j.logger.com.xiongluoluo.mapper=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

 

创建StudentMapper.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.xiongluoluo.mapper.StudentMapper">
    <!--多对多保存学生,先保存学生,再保存关系,一定要保存自动生长的主键-->
    <insert id="insertStudent" parameterType="Student" useGeneratedKeys="true" keyProperty="id" keyColumn="id">
        insert into t_stu(name) values(#{name})
    </insert>
    
    <insert id="insertRelation">
        insert into t_stu_tea(stu_id,tea_id) values(#{stuId},#{teaId})
    </insert>
</mapper>

 

 

创建StudentMapper.java:

package com.xiongluoluo.mapper;

import com.xiongluoluo.bean.Student;
import org.apache.ibatis.annotations.Param;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
public interface StudentMapper {
    /*保存学生*/
    public void insertStudent(Student student);
    /*保存关系,使用注解传参*/
    public void insertRelation(@Param("stuId")Integer stuId,@Param("teaId")Integer teaId);

}

创建StudentService.java:

package com.xiongluoluo.service;

import com.xiongluoluo.bean.Student;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
public interface StudentService {
    /*保存学生*/
    public void saveStudent(Student student);
}

 

创建StudentServiceImpl.java:

package com.xiongluoluo.service.impl;

import com.xiongluoluo.bean.Student;
import com.xiongluoluo.bean.Teacher;
import com.xiongluoluo.mapper.StudentMapper;
import com.xiongluoluo.service.StudentService;
import com.xiongluoluo.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
public class StudentServiceImpl implements StudentService {
    public void saveStudent(Student student) {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        mapper.insertStudent(student);//保存学生
        for(Teacher teacher : student.getTeacherList()){
            mapper.insertRelation(student.getId(),teacher.getId());
        }//保存关系
        sqlSession.commit();
        sqlSession.close();
        //查询可以不提交事务,增删改一定要记得提交事务
    }
}

 

创建测试类:

package com.xiongluoluo.test;

import com.xiongluoluo.bean.Student;
import com.xiongluoluo.bean.Teacher;
import com.xiongluoluo.service.StudentService;
import com.xiongluoluo.service.impl.StudentServiceImpl;
import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by Administrator on 2019/12/28 0028.
 */
public class MybatisTest {
    @Test
    public void test1(){
        Teacher teacher = new Teacher();
        teacher.setId(1);
        Teacher teacher1 = new Teacher();
        teacher1.setId(3);
        List<Teacher> teachers = new ArrayList<Teacher>();
        teachers.add(teacher);
        teachers.add(teacher1);

        Student student = new Student();
        student.setName("余洋");
        student.setTeacherList(teachers);


        StudentService studentService = new StudentServiceImpl();
        studentService.saveStudent(student);
    }
}