Spring Boot PUT请求传JSON对象报500错误求助

问题背景 #

用Java Spring Boot搭建REST后端控制器，前端通过Angular的HttpClient调用接口时出现500内部错误。曾尝试在请求体添加"parameters="，问题未解决，确认问题出在Java代码层面。

相关日志信息 #

OPTIONS "/api/adress/sav", parameters={}
Mapped to saveAdress(Adress)
Completed 200 OK
PUT "/api/adress/sav", parameters={}
Mapped to com.gcssara.hexa.application.AdressEndPoint#saveAdress(Adress)
Failed to complete request: java.lang.NullPointerException
Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
"ERROR" dispatch for PUT "/error", parameters={}
Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
Using 'application/json', given [application/json, text/plain, */*] and supported [application/json, application/*+json, application/json, application/*+json]
Writing [{timestamp=Tue Aug 30 14:41:23 CEST 2022, status=500, error=Internal Server Error, path=/api/adressm (truncated)...]
Exiting from "ERROR" dispatch, status 500

代码问题分析 #

Java控制器代码问题 #

原控制器方法未添加@RequestBody注解，Spring无法将请求体中的JSON数据绑定到Adresse参数，导致参数为null，调用adressService.saveAdress(adress)时触发空指针异常。

原代码：

@RestController
@RequestMapping("/api/adress")
@RequiredArgsConstructor
@CrossOrigin(origins = "*")
public class AdressEndPoint {

    @PutMapping(path ="/sav")
    public Adress saveAdress( Adresse adress) {
return adressService.saveAdress(adress);
    }

}

Angular请求代码问题 #

使用JSON.stringify(adress)将对象转为字符串，导致请求体格式为纯文本，请求头Content-Type被设为text/plain，而Spring默认期望application/json格式，引发415不支持的媒体类型错误（从请求头日志可见Status code:415）。

原代码：

createUpdate(adress:Adress, ) {
      return this._httpClient.put<Adress>(this.requestUrlBase +"/api/adress/sav",JSON.stringify(adress), {} );
    }

修复步骤 #

1. 修正Java控制器代码：给方法参数添加@RequestBody注解，让Spring自动解析请求体JSON到Adresse对象：

@RestController
@RequestMapping("/api/adress")
@RequiredArgsConstructor
@CrossOrigin(origins = "*")
public class AdressEndPoint {

    @PutMapping(path ="/sav")
    public Adress saveAdress(@RequestBody Adresse adress) {
return adressService.saveAdress(adress);
    }

}

2. 修正Angular请求代码：去掉JSON.stringify，直接传入adress对象，HttpClient会自动将对象序列化为JSON，并设置正确的Content-Type: application/json请求头：

createUpdate(adress:Adress) {
      return this._httpClient.put<Adress>(this.requestUrlBase +"/api/adress/sav", adress);
    }

3. 检查实体类配置：确保Adresse实体类具备无参构造器、getter和setter方法，保证Jackson能正确完成JSON反序列化。

内容的提问来源于stack exchange，提问作者Jack Boch