Required @QueryParam in JAX-RS (and what to do in their absence)

java, jax-rs

Solution

Good question. Unfortunately (or maybe fortunately) there is no mechanism in JAX-RS to make any params mandatory. If a parameter is not supplied it's value will be `NULL` and your resource should deal with it accordingly. I would recommend to use `WebApplicationException` to inform your users:

@GET
@Path("/some-path")
public String read(@QueryParam("name") String name) {
  if (name == null) {
    throw new WebApplicationException(
      Response.status(Response.Status.BAD_REQUEST)
        .entity("name parameter is mandatory")
        .build()
    );
  }
  // continue with a normal flow
}

Problem

I deploy a web-services component to JBoss Application Server 7 using the RESTEasy JAX-RS implementation. Is there an annotation available to declare required, mandatory @QueryParam parameters in JAX-RS ? And, if not, what is the 'standard' way to deal with situations where such parameters are missing? My web service (resource) methods return JSON-stringified results when properly invoked with all the mandatory arguments, but I'm not sure what is the best way to indicate to the caller that a required parameter was missing.

Original source

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