SpringData JPA一对多多对一多对多关联

一、一对多、多对一

　　1、Country实体类

　　2、City实体类

　　3、CountryDao层

4、CityDao层

5.Controller

package com.zn.controller;

import com.zn.dao.CityDao;

import com.zn.dao.CountryDao;

import com.zn.entity.City;

import com.zn.entity.Country;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.ResponseBody;

@Controller

public class CountryController {

    @Autowired

    CountryDao countryDao;

    CityDao cityDao;

    //级联添加

    @RequestMapping("/OneToMany")

    @ResponseBody

    public String AddCountry(){

        Country country1=new Country();

        country1.setCountry_name("中国");

        City city1=new City();

        city1.setCity_name("中国香港");

        City city2=new City();

        city2.setCity_name("中国台湾");

        //维护国家与城市的一对多关系

        country1.getCitys().add(city1);

        country1.getCitys().add(city2);

        countryDao.save(country1);

        return "SUCCESS";

    }

    //关联查询

    @RequestMapping("/getCountry")

    @ResponseBody

    public Object getCountry(){

        return countryDao.findAll();

    }

    //级联删除

    @RequestMapping("/deleteCountry")

    @ResponseBody

    public String deleteCountry(){

        //检索国家实体

        Country one=countryDao.getOne();

        countryDao.delete(one);

        return "SUCCESS";

    }

    //由城市到国家的关联查询

    @RequestMapping("/getCity")

    @ResponseBody

    public Object getCity(){

        return countryDao.findAll();

    }

}

二、多对多

　　1、TStudent实体类

　　　　

2、Teacher实体类 　　

3、Stu_TeaDao

4、Tea_StuDao　　

5、Controller

package com.zn.controller;

import com.zn.dao.Stu_TeaDao;

import com.zn.dao.Tea_StuDao;

import com.zn.entity.TStudent;

import com.zn.entity.Teacher;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.ResponseBody;

import java.util.Arrays;

import java.util.List;

@Controller

public class Stu_TeaController {

    @Autowired

    Stu_TeaDao stu_teaDao;

    @Autowired

    Tea_StuDao tea_stuDao;

    //添加学生和老师

    @RequestMapping("/addstu")

    @ResponseBody

    public String addstu(){

        TStudent student1=new TStudent("张三");

        TStudent student2=new TStudent("李四");

        TStudent student3=new TStudent("王五");

        Teacher teacher1=new Teacher("小王子");

        student1.getTeachers().add(teacher1);

        student2.getTeachers().add(teacher1);

        student3.getTeachers().add(teacher1);

        stu_teaDao.saveAll(Arrays.asList(student1,student2,student3));

        return "SUCCESS";

    }

    //多对多添加老师

    @RequestMapping("/addTea")

    @ResponseBody

    public String addTea(){

        Teacher teacher=new Teacher("王老师");

        List<TStudent> all = stu_teaDao.findAll();

        teacher.getStudents().addAll(all);

        tea_stuDao.save(teacher);

        return "SUCCESS";

    }

    //多对多关联查询(慎用！！死循环！！)

    @RequestMapping("/getTea")

    @ResponseBody

    public Object getTea(){

        return tea_stuDao.getOne();

    }

}