java - 在 Spring Boot 中通过 POST 创建对实体创建的父引用

Question

我目前正在尝试使用支持客户端和作业的 Spring Boot 构建 REST API。一个Client可以有多个Job，一个Job属于一个Client。但是，当我通过 client_id 或尝试查找 Client 对象保存引用 Client 的 Job 时，出现此错误:

{
  "timestamp" : 1479163164739,
  "status" : 400,
  "error" : "Bad Request",
  "exception" : "org.springframework.http.converter.HttpMessageNotReadableException",
  "message" : "Could not read document: Can not construct instance of com.core.model.Client: no String-argument constructor/factory method to deserialize from String value ('3')\n at [Source: java.io.PushbackInputStream@5138cca1; line: 1, column: 12] (through reference chain: com.core.model.Job[\"client\"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.core.model.Client: no String-argument constructor/factory method to deserialize from String value ('3')\n at [Source: java.io.PushbackInputStream@5138cca1; line: 1, column: 12] (through reference chain: com.core.model.Job[\"client\"])",
  "path" : "/api/v1/jobs"
}

包括我的 Job 和 Client 模型和 Controller :

我的工作模型:

package com.core.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.CascadeType;
import javax.persistence.Table;
import javax.persistence.Column;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Id;

@Entity
@Table(name="`job`")
public class Job {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="job_id")
    private Long jobId;

    @ManyToOne(cascade=CascadeType.ALL, targetEntity = Client.class)
    @JoinColumn(name = "client_id", nullable = false)
    private Client client;

    private String address1;
    private String address2;
    private String city;
    private String county;
    private String state;
    private String zip;
    private String country;
    private String description;

    //Note: I tried Long client_id instead of using the Client object here and same thing
    public Job(String description, String address1, String address2, String city, String county,
               String state, String zip, String country, Client client) {
        this.setDescription(description);
        this.setAddress1(address1);
        this.setAddress2(address2);
        ...
        this.setClient(client);
    }

    public Job() {}

    public Long getId() { return jobId; }
    public void setId(Long id) { this.jobId = id; }
    ...
    public Client getClient() { return client; }
    public void setClient(Client client) { this.client = client; }

}

工作 Controller :

package com.core.controller;

import com.core.model.Job;
import com.core.repository.JobRepository;
import org.apache.catalina.connector.Response;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import com.core.repository.JobRepository;
import org.springframework.hateoas.Resource;

import java.util.Collection;
import java.util.List;

@RestController
@RequestMapping("/api/v1/jobs")
public class JobController {

    @Autowired
    private JobRepository repository;

    @RequestMapping(method = RequestMethod.GET)
    public ResponseEntity<Collection<Job>> getAllJob(){
        return new ResponseEntity<>((Collection<Job>) repository.findAll(), HttpStatus.OK);
    }
    @RequestMapping(method = RequestMethod.GET, value = "/{id}")
    public ResponseEntity<Job> getEquipmentWithId(@PathVariable Long id) {
        return new ResponseEntity<>(repository.findOne(id),HttpStatus.OK);
    }

    @RequestMapping(value="", method=RequestMethod.POST)
    public ResponseEntity createNew(@RequestBody Job job) {
        repository.save(job);
        return new ResponseEntity(job, HttpStatus.CREATED);
    }
}

和客户端模型:

package com.core.model;

import javax.persistence.Entity;
import javax.persistence.Access;
import javax.persistence.AccessType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Table;
import javax.persistence.Column;
import javax.persistence.JoinColumn;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entity
@Table(name="`client`")
public class Client {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="client_id")
    @Access(AccessType.PROPERTY)
    private Long clientId;

    public Client(String description) {
        this.setDescription(description);
    }

    public Client() {}

    public Long getClientId() {
        return clientId;
    }
    public void setClientId(Long id) { this.clientId = id; }
    ...
}

我只想将该客户端 ID 保存到作业中，这里的正确方法是什么？

Answer 1

我的猜测是您正在尝试使用 REST 调用此方法:

@RequestMapping(value="", method=RequestMethod.POST)
public ResponseEntity createNew(@RequestBody Job job) {
        repository.save(job);
        return new ResponseEntity(job, HttpStatus.CREATED);
}

这个异常(exception)很清楚，它谈到:

com.fasterxml.jackson.databind.JsonMappingException

这意味着无论何时您尝试在请求正文中传递 Job 实体，Jackson 都无法将其绑定(bind)到方法 Controller 上的 Job job 参数。

我的建议是尝试编写 Jackson 反序列化器类，它将告诉 Jackson 究竟如何进行反序列化。

这是一个如何做到这一点的例子:

Right way to write JSON deserializer in Spring or extend it