Scenario: Validate Query Parameter Passed in by the Caller

Steps

• Implement filter
• Extracts query parameter from ContainerRequestContext
• Performs the validation – aborts the request with an appropriate response status (and the error message)

@Provider
@QueryParamValidator
public class JAXRSReqFilter implements ContainerRequestFilter {

    @Override
    public void filter(ContainerRequestContext requestContext) throws IOException {

        MultivaluedMap < String, String > queryParameters = requestContext.getUriInfo().getQueryParameters();

        String queryParam = queryParameters.keySet().stream().findFirst().get();
        System.out.println("Query param - " + queryParam);

        if (!queryParam.equals("p")) {
            requestContext.abortWith(Response
                .status(Response.Status.BAD_REQUEST)
                .entity("Invalid Query Param " + queryParam)
                .build());
        }
    }
}

Enforce Filter

• Use @NameBinding to decorate custom annotation
• Use the custom annotation on the JAX-RS method

@NameBinding
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
public @interface QueryParamValidator {
    
}

@Path("test")
public class TestResource {
    
    @GET
    @QueryParamValidator
    public String test(@QueryParam("p") String p){
        return "Param "+ p + " on " + new Date();
    }
}

Further Reading

• My eBook: REST assured with JAX-RS
• This JAX-RS 2.0 article in the Java Magazine

Cheers!