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(5);
        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();
    }


}

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