sending a multipartFile from Angular to Java-CodePudding

I'm creating an API with Java, and I'm facing a problem with files.

This is my API definition:

@RequestMapping(value="/createUser", method = RequestMethod.POST)
ResponseEntity<?> fromFile(@RequestBody FileRequest FileRequest);

This FileRequest input Bean only have one item (while I solve the problem) but in future it will have more items such other form data as userName or userAge.

public class FromFileRequest {

  @NotEmpty(message = "Value for input 'file' can't be null" )
  private MultipartFile file;

  public MultipartFile getFile() {
    return file;
  }

  public void setFile(MultipartFile file) {
    this.file = file;
  }
}

In the angular side:

load(file: File): Observable<any> {
    let formData: FormData = new FormData();    
    formData.append('file', file);
    return this.apiService.post('/api/createFile', formData);
}

I receive an error in Java side

09:31:51,010 INFO [stdout] (http-127.0.0.1:8080-4) org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.springframework.web.multipart.MultipartFile]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.web.multipart.MultipartFile` (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
09:31:51,010 INFO [stdout] (http-127.0.0.1:8080-4) at [Source: (PushbackInputStream); line: 1, column: 9] (through reference chain: com.mypackage.api.dto.FileRequest["file"])
09:31:51,010 INFO [stdout] (http-127.0.0.1:8080-4) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:242) ~[spring-web-5.1.2.RELEASE.jar:5.1.2.RELEASE]
09:31:51,010 INFO [stdout] (http-127.0.0.1:8080-4) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:227) ~[spring-web-5.1.2.RELEASE.jar:5.1.2.RELEASE]

I really don't know if the problem is in angular or Java side, because if I just use the MultipartFile type as the input in my API (and modify angular properly) it works.

CodePudding user response：

You can not use a @RequestBody you have to use a @RequestPart

@RequestMapping(value="/createUser", method = RequestMethod.POST, consumes = {MediaType.MULTIPART_FORM_DATA_VALUE})
ResponseEntity<?> fromFile(@RequestPart(value = "file") MultipartFile file)

And if you need to send a DTO with your file,

stringify it manually on the angular side :

formData.append('dto', JSON.stringify(data));

on the Java part add another @RequestPart(value = "dto") String stringDTO)
call manually your object mapper :

YourDtoClass dto = objectMapper.readValue(stringDTO, YourDtoClass.class);

objectMapper from package com.fasterxml.jackson.databind