CODEWITHSUNDEEP
javarestjax-rs
Anveshan
Anveshan

Reputation: 624

Default MIME types for REST resource methods

I am trying to understand the MIME types in RESTful services.If there is a resource method (sayHello) as in below

@Path("/customers")
public class CustomerResource {
    @GET
    public String sayHello(){
        return "Hello World";
    }
}

I didn't put any @Produces or @Consumes annotation on the above method. I have below questions.

  1. Is there any default MIME type above method uses to send the response ?
  2. Or Does it produce response content type based on "accept-type" from incoming request ?
  3. Can it happen that request does not specify what content type does it accept ? If that is the case, what response content type does above resource method will produce ?

Thanks in advance.

Upvotes: 2

Views: 1991

Answers (1)

Paul Samsotha
Paul Samsotha

Reputation: 208974

Often it will default to application/octet-stream, unless the client set the Accept header, in which case, that's the type that will be used.

One thing you need to be careful about is that there is a not a MessageBodyWriter to handle application/octet-stream and most types. For instance say you have

@GET
public SomeModel get() {}

If the client doesn't set a Accept: application/json header, then the runtime will look for a MessageBodyWriter to that can serialize SomeModel to application/octet-stream, and it will fail and you will get an exception saying something like "No MessageBodyWriter found for mediatype application/octet-stream and type SomeModel".

So it is always a good idea to put the @Produces. Another benefit is that you determine what types the endpoint can produce. For instance if you have @Produces("application/json"), and the client set the Accept: application/xml header, then they will get a 406 Not Acceptable error code, which is what should happen.

Notice the first paragraph, I used the word Often. It is not always the case. For some instances, the the runtime will make assumptions based on the return type. For instance if you return a String it is likely the runtime will choose text/plain.

But like I said, it's always better to have the @Produces and @Consumes annotations. These are hints not just for the developer but for the runtime to make decisions.

Upvotes: 1

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