发布数据时为空

本文介绍了发布数据时为空的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在使用邮递员来处理 spring boot api.目前我正在尝试将数据添加到相关表中.其中有2个地区和城镇.城镇有一个 regionid 列.这是我的要求.

I am using a postman to work with spring boot api. Currently I am trying to add data to a related table. There are 2 of them regions and towns. Towns has a regionid column. Here is my request.

{ "name": "test", "regionid":"2" }

虽然名称发布得很好，但区域 ID 为空.我正在尝试在控制器中打印出来.这是它的保存数据方法:

While name is posting just fine, region id is null. I am trying to print it out in a controller. Here is a save data method of it:

@PostMapping("/add") public ResponseEntity<Towns> createtown(@RequestBody Towns town) { try { Towns _town = townsrepository .save(new Towns( town.getName(), town.getRegionid())); return new ResponseEntity<>(_town, HttpStatus.CREATED); } catch (Exception e) { System.out.println(e.getMessage()); System.out.println("region"); System.out.println(town.getRegionid()); return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR); } }

我遇到了异常，在打印 town.getName() 时我得到了测试.但是，当我尝试打印出 town.getRegionId() 时，我得到了空值.这是我的模型类

I am getting the exception and while I am printing town.getName() I get test. But while I try to print out town.getRegionId() I get null. Here is my model class

package com.example.model; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import org.hibernate.annotations.OnDelete; import org.hibernate.annotations.OnDeleteAction; @Entity @Table(name = "towns") public class Towns { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; @Column(name = "name") private String name; @ManyToOne(fetch = FetchType.LAZY, optional = false) @JoinColumn(name = "regionid", nullable = false) @OnDelete(action = OnDeleteAction.CASCADE) private Regions regionid; public Towns() { } public Towns(String name,Regions regionid) { // super(); this.id=id; this.name = name; this.regionid=regionid; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Regions getRegionid() { return regionid; } public void setRegionid(Regions regionid) { this.regionid = regionid; } }

还有存储库:

package com.example.repository; import java.util.List; import org.springframework.data.domain.Page; import org.springframework.data.domain.Pageable; import org.springframework.data.jpa.repository.JpaRepository; import java.util.Optional; import com.example.model.Towns; import com.example.model.Regions; public interface TownsRepository extends JpaRepository<Towns, Integer> { List<Towns> findByNameContaining(String name); Page<Regions> findByregionid(Integer regionid, Pageable pageable); Optional<Regions> findByregionidAndId(Integer regionId, Integer id); }

还有 Application.properties 以防万一

And Application.properties in case it will help

spring.datasource.url= jdbc:mysql://localhost:3306/appartmentbuilderbase?useSSL=false spring.datasource.username= root spring.datasource.password= spring.jpa.properties.hibernate.dialect= org.hibernate.dialect.MySQL5InnoDBDialect spring.jpa.hibernate.ddl-auto= update

我在这里做错了什么?

尝试按照建议进行:

Towns _town = townsrepository .save(new Towns( town.getName(), regionsrepository.findById(town.getRegionid())));

得到了这些错误:

Description Resource Path Location Type The constructor Towns(String, Optional<Regions>) is undefined TownsController.java /apartmentbuilders/src/main/java/com/example/controller line 71 Java Problem

还有这个:

Description Resource Path Location Type The method save(S) in the type CrudRepository<Towns,Integer> is not applicable for the arguments (Towns) TownsController.java /apartmentbuilders/src/main/java/com/example/controller line 71 Java Problem

添加完整的控制器代码

package com.example.controller; import java.util.ArrayList; import java.util.List; import java.util.Optional; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.CrossOrigin; import org.springframework.web.bind.annotation.DeleteMapping; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.PutMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; import com.example.model.Towns; import com.example.repository.TownsRepository; import com.example.repository.RegionsRepository; @CrossOrigin(origins = "localhost:8081") @RestController @RequestMapping("/towns") public class TownsController { @Autowired TownsRepository townsrepository; @Autowired RegionsRepository regionsrepository; @GetMapping("/list") public ResponseEntity<List<Towns>> getAllTowns(@RequestParam(required = false) String name) { try { List<Towns> towns = new ArrayList<Towns>(); if (name == null) townsrepository.findAll().forEach(towns::add); else townsrepository.findByNameContaining(name).forEach(towns::add); if (towns.isEmpty()) { return new ResponseEntity<>(HttpStatus.NO_CONTENT); } return new ResponseEntity<>(towns, HttpStatus.OK); } catch (Exception e) { return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR); } } @GetMapping("/list/{id}") public ResponseEntity<Towns> getTownById(@PathVariable("id") int id) { Optional<Towns> townData = townsrepository.findById(id); if (townData.isPresent()) { return new ResponseEntity<>(townData.get(), HttpStatus.OK); } else { return new ResponseEntity<>(HttpStatus.NOT_FOUND); } } @PostMapping("/add") public ResponseEntity<Towns> createtown(@RequestBody Towns town) { try { Towns _town = townsrepository .save(new Towns( town.getName(), town.getRegionid())); // Towns _town = townsrepository .save(new Towns( town.getName(), regionsrepository.findByRegionId(town.getRegionid()))); return new ResponseEntity<>(_town, HttpStatus.CREATED); } catch (Exception e) { System.out.println(e.getMessage()); System.out.println("region"); System.out.println(town.getRegionid()); return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR); } } @PutMapping("/edit/{id}") public ResponseEntity<Towns> updateTown(@PathVariable("id") int id, @RequestBody Towns town) { Optional<Towns> townData = townsrepository.findById(id); if (townData.isPresent()) { Towns _town = townData.get(); _town.setName(town.getName()); _town.setRegionid(town.getRegionid()); return new ResponseEntity<>(townsrepository.save(_town), HttpStatus.OK); } else { return new ResponseEntity<>(HttpStatus.NOT_FOUND); } } @DeleteMapping("/delete/{id}") public ResponseEntity<HttpStatus> deleteTown(@PathVariable("id") int id) { try { townsrepository.deleteById(id); return new ResponseEntity<>(HttpStatus.NO_CONTENT); } catch (Exception e) { return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR); } } }

添加区域存储库

package com.example.repository; import java.util.List; import org.springframework.data.jpa.repository.JpaRepository; import com.example.model.Regions; public interface RegionsRepository extends JpaRepository<Regions, Integer> { List<Regions> findByNameContaining(String name); }

推荐答案

你缺少一个 DTO 类.不要直接将 DB 实体类映射到请求正文.有一个类似的课程

You are missing a DTO class. Don't directly map DB entity class to request body. have a class like

@Data public class TownDTO { private String name; private String regionid; }

同样在保存时，通过存储库获取区域:

also when saving, get the region through a repository:

Towns _town = townsrepository .save(new Towns( town.getName(), regionRepository.findByRegionId(town.regionId)));

所以在控制器中:

@PostMapping("/add") public ResponseEntity<Towns> createtown(@RequestBody Town town) { try { Towns _town = townsrepository .save(new Towns( town.getName(), regionRepository.findByRegionId(town.regionId))); return new ResponseEntity<>(_town, HttpStatus.CREATED); } catch (Exception e) { System.out.println(e.getMessage()); System.out.println("region"); System.out.println(town.getRegionid()); return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR); } }