How to use RestTemplate with multiple response types?

java spring spring-rest
membersound picture membersound · Mar 4, 2016 · Viewed 11.6k times · Source

I'm using spring RestTemplate for communication with a xml webservice backend as follows:

ResponseEntity<MainDTO> dto = restTemplate.postForObject(url, postData, MainDTO.class);

Problem: the backend might either respond with MainDTO for normal data or with ErrorDTO in case of failures. But both with HTTP 200.

But I don't know which object will come back before! Anyways restTemplate requires me to pass the class type before.

So, how could I parse the xml either to normal or the error bean?

Sidenote: I don't have any control of the webservice backend.

Answer

rastadrian picture rastadrian · Mar 4, 2016

As you would figure, the problem is that the backend should return you errors with HTTP error codes, that's what they are there for.

But as you said, you don't have control over the backend so what you can do is first get it as a String

ResponseEntity<String> dto = restTemplate.postForObject(url, postData, String.class);

Then you can attempt to parse the string response as a MainDTO with either Jackson or Gson (whatever you have in your project, which you should, because I believe Spring's RestTemplate uses either on of them internally) with a try/catch and if it fails, then you try with to parse it with your ErrorDto.

Update

Oh, I just read that it was an XML service, not a JSON on, the approach above is still valid, but instead of using Jackson or Gson, you can use SimpleXML (http://simple.sourceforge.net/download/stream/doc/tutorial/tutorial.php#deserialize) which allows you to deserialize XML in an "easy" way, you just need to annotate your models with their annotations which are described in their tutorials and examples.

This Spring's example (http://spring.io/guides/gs/consuming-rest-xml-android/) might also provide an insight in how to use SimpleXML.

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