mybatis多对多关联实战教程(推荐)

2023-09-22 17:15:06 334

MyBatis3.0添加了association和collection标签专门用于对多个相关实体类数据进行级联查询，但仍不支持多个相关实体类数据的级联保存和级联删除操作

一、创建student、teacher和stu_teach_rel三张张表

DROPTABLEIFEXISTS`student`;
CREATETABLE`student`(
`id`int(11)NOTNULL,
`name`varchar(255)DEFAULTNULL,
`age`int(11)DEFAULTNULL,
`gender`varchar(255)DEFAULTNULL,
PRIMARYKEY(`id`)
)ENGINE=InnoDBDEFAULTCHARSET=utf8;

INSERTINTO`student`VALUES('1','刘德华','55','0');
INSERTINTO`student`VALUES('2','张惠妹','49','1');
INSERTINTO`student`VALUES('3','谢霆锋','35','0');
INSERTINTO`student`VALUES('4','王菲','47','1');
INSERTINTO`student`VALUES('5','汪峰','48','0');
INSERTINTO`student`VALUES('6','章子怡','36','1');

DROPTABLEIFEXISTS`teacher`;
CREATETABLE`teacher`(
`id`int(11)NOTNULL,
`name`varchar(255)DEFAULTNULL,
`gender`varchar(255)DEFAULTNULL,
`subject`varchar(255)DEFAULTNULL,
`degree`varchar(255)DEFAULTNULL,
PRIMARYKEY(`id`)
)ENGINE=InnoDBDEFAULTCHARSET=utf8;

INSERTINTO`teacher`VALUES('1','王晶','0','CHINESE','大专');
INSERTINTO`teacher`VALUES('2','冯小刚','0','ENGLISH','本科');
INSERTINTO`teacher`VALUES('3','吴京','0','MATHEMATICS','大专');
INSERTINTO`teacher`VALUES('4','王倦','1','MATHEMATICS','研究生');

DROPTABLEIFEXISTS`stu_teach_rel`;
CREATETABLE`stu_teach_rel`(
`id`int(11)NOTNULL,
`stu_id`int(11)NOTNULL,
`teach_id`int(11)NOTNULL,
PRIMARYKEY(`id`)
)ENGINE=InnoDBDEFAULTCHARSET=utf8;


INSERTINTO`stu_teach_rel`VALUES('1','1','1');
INSERTINTO`stu_teach_rel`VALUES('2','2','1');
INSERTINTO`stu_teach_rel`VALUES('3','1','2');
INSERTINTO`stu_teach_rel`VALUES('4','2','2');
INSERTINTO`stu_teach_rel`VALUES('5','2','3');
INSERTINTO`stu_teach_rel`VALUES('6','3','1');
INSERTINTO`stu_teach_rel`VALUES('7','3','2');
INSERTINTO`stu_teach_rel`VALUES('8','1','3');
INSERTINTO`stu_teach_rel`VALUES('9','4','1');
INSERTINTO`stu_teach_rel`VALUES('10','4','2');
INSERTINTO`stu_teach_rel`VALUES('11','5','3');
INSERTINTO`stu_teach_rel`VALUES('12','5','4');
INSERTINTO`stu_teach_rel`VALUES('13','6','1');
INSERTINTO`stu_teach_rel`VALUES('14','6','3');

二、新建和表相关的实体类

packagecom.yihaomen.mybatis.model;
importcom.yihaomen.mybatis.enums.Gender;
importjava.util.List;

publicclassStudent{
privateStringid;
privateStringname;
privateintage;
privateGendergender;
privateListteachers;

setters&getters

}

packagecom.yihaomen.mybatis.model;
importcom.yihaomen.mybatis.enums.Gender;
importcom.yihaomen.mybatis.enums.Subject;
importjava.util.List;

publicclassTeacher{
privateintid;
privateStringname;
privateGendergender;
privateSubjectsubject;
privateStringdegree;
privateListstudents;

setters&getters
}

三、新建映射关系

packagecom.yihaomen.mybatis.dao;
importcom.yihaomen.mybatis.model.Student;
importorg.springframework.stereotype.Repository;
importjava.util.List;

@Repository
publicinterfaceStudentMapper{
ListselectStudents();
}

student.xml




















SELECT
s.id,s.name,s.gender,t.idteach_id,t.nametname,t.gendertgender,t.subjecttsubject,t.degreetdegree
FROM
students
LEFTJOIN
stu_teach_relstr
ON
s.id=str.stu_id
LEFTJOIN
teachert
ON
t.id=str.teach_id

四、在configuration.xml中配置相关mapper

五、测试

packagecom.yihaomen.service.student;
importcom.yihaomen.mybatis.dao.StudentMapper;
importcom.yihaomen.mybatis.model.Student;
importcom.yihaomen.mybatis.model.Teacher;
importcom.yihaomen.service.BaseTest;
importorg.apache.ibatis.session.SqlSession;
importorg.apache.ibatis.session.SqlSessionFactory;
importjava.util.List;

publicclassTestStudentextendsBaseTest{
publicstaticvoidtestStuTeachRela(){
SqlSessionFactorysqlSessionFactory=getSession();
SqlSessionsession=sqlSessionFactory.openSession();
StudentMappermapper=session.getMapper(StudentMapper.class);
Listlist=mapper.selectStudents();

for(Students:list){
System.out.println("------------------");
System.out.println(s.getName()+","+s.getAge()+","+s.getGender());
for(Teachert:s.getTeachers()){
System.out.println(t.getName()+","+t.getGender()+","+t.getSubject());
}
}
}

publicstaticvoidmain(String[]args){
testStuTeachRela();
}
}

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mybatis多对多关联实战教程(推荐)

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