Spring REST - Can a RestTemplate consume multipart/mixed? - spring

Question

I want to write a REST service which does responed with a zipFile and some json data, everything in one multipart/mixed request.
The server part works fine and i am testing it with the REST Client from firefox. My Server sends a multipart like this
--k-dXaXvCFusLVXUsg-ryiHMmkdttadgcBqi4XH
Content-Disposition: form-data; name="form"
Content-type: application/json
{"projectName":"test","signal":"true"}
--k-dXaXvCFusLVXUsg-ryiHMmkdttadgcBqi4XH
Content-Disposition: form-data; name="file2"; filename="file2.txt"
Content-type: application/octet-stream
Content-Length: 10
hallo=Welt
I know that RestTemplate can send multiparts with the help of a MultiValueMap out of the box.
Now I tried to consume multipart/mixed responses and return a MultiValueMap
#Component
public class RestCommand
extends AbstractLoginRestCommand<Form, MultiValueMap<String, Object>>
{
#Override
protected MultiValueMap<String, Object> executeInternal ( Form form )
{
RestTemplate restTemplate = getRestTemplate();
MyMultiValueMap map = restTemplate.postForObject(getUrl(), form, MyMultiValueMap.class);
return new LinkedMultiValueMap<String, Object>(map);
}
}
class MyMultiValueMap extends LinkedMultiValueMap<String, Object>
{}
MyMultiValueMap exist to prevent type erasure (generics).
This gives
org.springframework.web.client.RestClientException: Could not extract
response: no suitable HttpMessageConverter found for response type
[class org.jlot.client.remote.MyMultiValueMap] and content type
[multipart/form-data;boundary=Rjh-fkdsI9OIyPpYwdFY7lsUIewhRSX8kE19I;charset=UTF-8]
at
org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:107)
at
org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:492)
Javadoc of FormHttpMessageConverter says it can write but not read multipart/form-data.
Why is it like this?
Is there a way to read multipart/form-data with RestTemplate out-of-the-box or do I need to write a HttpMessageConverter?

Answer 1

I had the same issue and I think I achieved what you wanted.
You just have to override the canRead method of the form converter. With your example something like below should work.
FormHttpMessageConverter formConverter = new FormHttpMessageConverter() {
#Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
if (clazz == MyMultiValueMap.class) {
return true;
}
return super.canRead(clazz, mediaType);
}
};
And add this converter to your rest template.

Answer 2

I use this solution at the moment:
#ResponseBody
#PostMapping(value = JlotApiUrls.PUSH, produces = "application/json")
public List<PushResultDTO> push (
#PathVariable String projectName,
#PathVariable String versionName,
#RequestPart("file") MultipartFile multipartFile,
#RequestPart("data") #Valid PushForm pushForm
) throws IOException, BindException
{
...
}
https://github.com/kicktipp/jlot/blob/master/jlot-web/src/main/java/org/jlot/web/api/controller/PushController.java