How to fix multipart/form-data MediaType not being set with Jackson Spring MVC - spring

Question

I'm trying to send a Product and product images from Angular 7 frontend to a SpringMVC backend.
To add support for Multipart files I've added this bean inside my AppConfig.
#Bean(name = "multipartResolver")
public CommonsMultipartResolver multipartResolver() {
CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver();
multipartResolver.setMaxUploadSize(1000000);
return multipartResolver;
}
Since I want to receive the Product object separately inside the controller I'm using #RequestPart to fetch both separately like this:
#RequestMapping(value = "save", method = RequestMethod.POST)
public ResponseEntity addProduct(#Valid #RequestPart Product product, #RequestPart MultipartFile[] images, BindingResult bindingResult, HttpServletRequest
}
On the frontend I'm adding the image to FormData like this:
let formData = new FormData();
formData.append('product', new Blob([JSON.stringify(this.product)],{ type: "application/json" }));
// I iterate and append all the images like this
formData.append('image[]', this.images, this.images.name);
this.http.post(this.appService.getApiUrl() + "api/product/save/", product);
The problem is that whenever I submit the form, I get this exception as a response: HTTP Status 415 – Unsupported Media Type.
I tried debugging this issue by setting breakpoints inside CommonsMultipartResolver class and after tracing the request through the code I've found that when the getSupportedMediaTypes() is called it returns only two media types:
application/json
application/*+json
Inside the following method in AbstractHttpMessageConverter:
protected boolean canRead(#Nullable MediaType mediaType) {
if (mediaType == null) {
return true;
} else {
Iterator var2 = this.getSupportedMediaTypes().iterator();
MediaType supportedMediaType;
do {
if (!var2.hasNext()) {
return false;
}
supportedMediaType = (MediaType)var2.next();
} while(!supportedMediaType.includes(mediaType));
return true;
}
}
Finding this I tried adding MediaType.MULTIPART_FORM_DATA like this inside AppConfig:
#Override
public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
for (HttpMessageConverter converter : converters) {
if (converter instanceof MappingJackson2HttpMessageConverter) {
List<MediaType> types = new ArrayList<>();
types.add(MediaType.APPLICATION_JSON);
types.add(MediaType.APPLICATION_JSON_UTF8);
types.add(MediaType.MULTIPART_FORM_DATA);
((MappingJackson2HttpMessageConverter) converter).setSupportedMediaTypes(types);
Hibernate5Module hibernate5Module = new Hibernate5Module();
hibernate5Module.disable(Hibernate5Module.Feature.USE_TRANSIENT_ANNOTATION);
ObjectMapper mapper = ((MappingJackson2HttpMessageConverter) converter).getObjectMapper();
mapper.registerModule(hibernate5Module);
}
}
}
But it still wouldn't work. When the app starts up, I do see the constructor of AbstractJackson2HttpMessageConverter being called with my MediaTypes but they get overwritten by more calls to the same constructor after it.
Is there any way I can get the MediaType to persist? I might be looking in the wrong direction so any insight will be helpful.

Answer 1

The Jackson library is required on the classpath. Spring does not declare this by default. Make sure that at least com.fasterxml.jackson.core:jackson-databind is available in the classpath of the Spring MVC application. Example for Apache Maven:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson.version}</version>
</dependency>
Example for the jackson.version value: 2.9.0

Answer 2

1) You need to give input data supported at server end. Since you are sending File, means server is consuming the Multipart Data.
For multipart we need to set consumes = "multipart/form-data"
#RequestMapping(value = "save", method = RequestMethod.POST, consumes = "multipart/form-data")
public ResponseEntity addProduct(#Valid #RequestPart Product product, #RequestPart MultipartFile[] images, BindingResult bindingResult, HttpServletRequest
}
2) Since form is sending multipart data we need to set content-type at front end too in http header in post call.
content-type: multipart/form-data"