我面临**JSON解析错误:无法反序列化Spring Boot项目中的`java.util.HashSet`的实例,因为它超出了Start_Object内标识** [英] I am facing **JSON parse error: Cannot deserialize instance of `java.util.HashSet` out of START_OBJECT token** in Spring Boot project
本文介绍了我面临**JSON解析错误:无法反序列化Spring Boot项目中的`java.util.HashSet`的实例,因为它超出了Start_Object内标识**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
我收到JSON分析错误:当我尝试保存与一对多关系映射到我的另一个POJO的POJO类对象时,无法使用我的Spring Boot项目反序列化java.util.HashSet
的java.util.HashSet
的实例。我不确定我在邮递员中发送的JSON格式是否正确。我正在尝试保存定义了集合元素集的持久类的值。
父POJO类:
package com.example.demo.model;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name = "vendor")
public class Vendor {
@Id
int vendorId;
@Column
String vendorName;
@OneToMany(fetch = FetchType.LAZY, targetEntity = Customer.class, cascade = CascadeType.ALL)
@JoinColumn(name = "vendorId")
Set children;
public int getVendorId() {
return vendorId;
}
public void setVendorId(int vendorId) {
this.vendorId = vendorId;
}
public String getVendorName() {
return vendorName;
}
public void setVendorName(String vendorName) {
this.vendorName = vendorName;
}
public Set getChildren() {
return children;
}
public void setChildren(Set children) {
this.children = children;
}
}
儿童POJO类:
package com.example.demo.model;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.annotations.GeneratorType;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
@Entity
@Table(name = "customer")
public class Customer {
@Id
@GeneratedValue(strategy= GenerationType.AUTO)
int customerId;
@Column
String customerName;
public int getCustomerId() {
return customerId;
}
public void setCustomerId(int customerId) {
this.customerId = customerId;
}
public String getCustomerName() {
return customerName;
}
public void setCustomerName(String customerName) {
this.customerName = customerName;
}
}
控制器:
package com.example.demo.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import com.example.demo.model.Vendor;
import com.example.demo.service.VendorDataSaveService;
@RestController
public class VendorSaveController {
@Autowired
private VendorDataSaveService dataSaveService;
@PostMapping("/save")
public void saveVendor(@RequestBody Vendor vendor) {
dataSaveService.saveVendorRecord(vendor);
}
}
服务类别:
package com.example.demo.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.example.demo.model.Vendor;
import com.example.demo.repository.VendorDataSaveRepository;
@Service
public class VendorDataSaveService {
@Autowired
private VendorDataSaveRepository repository;
public void saveVendorRecord(Vendor vendor) {
repository.save(vendor);
}
}
存储库类:
package com.example.demo.repository;
import org.springframework.data.jpa.repository.JpaRepository;
import com.example.demo.model.Vendor;
public interface VendorDataSaveRepository extends JpaRepository<Vendor, Integer> {
}
我从邮递员那里发送的JSON格式:
"vendorId" : 101,
"vendorName" : "JAIN BOOKS",
"children" : {
"customerId" : 1,
"customerName" : "AMIT"
}
}
我在控制台上收到此错误消息:-
无法读取HTTp消息:org.springframework.http.converter.HttpMessageNotReadableException:JSON分析错误:无法反序列化java.util.HashSet
的实例超出START_OBJECT标记;嵌套异常是com.fasterxml.jackson.databind.exc.MismatchedInputException:无法反序列化java.util.HashSet
的实例超出START_OBJECT标记 在[来源:(Pushback InputStream);行:4,列:15](通过参考链:com.example.demo.model.Vendor["children"])
我需要改进什么?
推荐答案
的确,JB Nizet在评论中指出了这一点。Jackson告诉您,它正试图将JSON反序列化为一个Set
(java.util.HashSet
),这是一个集合,但该文件部分的JSON是一个对象START_OBJECT
。它不知道如何把一个物体变成一套,所以它放弃了。错误位于Vendor["children"]
您的请求包含以下针对儿童的内容:
"children" : {
"customerId" : 1,
"customerName" : "AMIT"
}
因为children
是一个集合,如果您想要一个孩子,它应该是这样的:
"children" : [
{
"customerId" : 1,
"customerName" : "AMIT"
}
]
这将是JSON中的对象数组,它将与Customer
的Set
很好地对应。
这篇关于我面临**JSON解析错误:无法反序列化Spring Boot项目中的`java.util.HashSet`的实例,因为它超出了Start_Object内标识**的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
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