无法将类型 'java.lang.String' 的值转换为所需类型的模型对象

Question

我正在尝试通过以 JSON 格式提供所需的请求来使用邮递员命中服务：

{
"baseParam": {
"userId": "u1234"
},
"resource": {
"name": "resource"
}
}

以及一个多部分文件，如下面的邮递员屏幕所示

邮递员屏幕

但是我收到错误：

"无法将类型'java.lang.String'的值转换为所需的类型'SampleRequestObject';嵌套异常是java.lang.IllegalStateException：无法将类型[java.lang.String]的值转换为所需类型">

控制器

@RequestMapping(method = RequestMethod.POST, value = "/sample/resource", 
produces = "application/json")
@ResponseBody
public final ResponseObject sampleResource(@RequestParam("request") final 
SampleRequestObject requestObject,@RequestParam("file") final 
MultipartFile file,BindingResult result ) throws IOException {
String success = “SUCCESS”;
requestObject.setFile(file);
String id=sampleService.sampleResourceService(resourceObject);   
//sampleService Object has been autowired earlier in controller              
return  success;                                                                                                       

}  
}

样本请求对象 – 模型类

public class SampleRequestObject extends SampleMainObject {
@NotNull
@IsValid(baseParam = { "userId"})
private BaseParam baseParam;
@NotNull    
private SampleResource resource;   // ANOTHER OBJECT OF SAMPLE RESOURCE 
CLASS
private MultipartFile file;
public SampleResource getResource() {
return resource;
}
public void setResource(SampleResource resource) {
this.resource = resource;
}
@Override
public Param getBaseParam() {
return baseParam;
}
public final void setBaseParam(final BaseParam baseParam) {
this.baseParam = baseParam;
}
public MultipartFile getFile() {
return file;
}
public void setFile(MultipartFile file) {
this.file = file;
}   
}

SampleServiceImpl.class (SampleService Implemetation( 中的函数

@Override
@Transactional
public final String sampleResourceService( SampleRequestObject 
requestObject) {throws IOException
String Id=null;
try
{
MainResourceObject resourceObject = new MainResourceObject();
resourceObject.setActualName(requestObject.getFile()
.getOriginalFilename());
resourceObject.setName(requestObject.getResource().getName()); );   
.
.
.
.  
.
.
.
.  
.  
}
catch (Exception e) {
log.error("Service Execution failed",e);
}
}

我也试着给@ModelAttribute而不是@RequestParam。然后，可以输入控制器和服务，但 requestObject 的所有值(在控制器中(都填充为 null 值。因此，它从服务实现中抛出 NullPointeException。

请提供解决方案。

Answer 1

你能试试这个吗

public final ResponseObject sampleResource(SampleRequestObject request,
@RequestParam("file") final MultipartFile file,
BindingResult result ) throws IOException {
...

我刚刚删除了@RequestParam并将变量更改为request