The following example demonstrates extracting and parsing representation constraints from the request's contextual information using the RepresentationConstaints utility:

@Path("/demo/bookstore/books")

public class BookStoreService {

  @Context

  // injected by the REST container

  private HttpServletRequest servletRequest;

  /**

   * Retrieves a {@link BookResource} representation of book with identifier {@code bookId}. The {@link BookResource}

   * representation shall include all of the mandatory and any of the optional fields annotated with {@code GET}.

   * Resource field exclusion and inclusion may be applied based on the presence of {@link QueryParameters#EXCLUDE} and

   * {@link QueryParameters#INCLUDE} query parameters or {@link HttpHeaders#X_REPRESENTATION_EXCLUDE} and

   * {@link HttpHeaders#X_REPRESENTATION_INCLUDE} HTTP headers, which values must represent a comma separated list of

   * any of the fields of the book resource.

   ....

   * Supported HTTP headers:

   * <ul>

   * <ol>

   * {@link QueryParameters#EXCLUDE} - This query parameter defines a list of resource fields that need to be excluded

   * from the representation. The value of the header shall be a comma separated list of field names which need to be

   * excluded.

   * </ol>

   * <ol>

   * {@link QueryParameters#INCLUDE} - This query parameter defines a list of resource fields that will be selectively

   * included in the representation, fields from the default resource representation which are not listed here will be

   * excluded.

   * </ol>

   * </ul>

   *

   * Supported query parameters:

   * <ul>

   * <ol>

   * {@link QueryParameters#EXCLUDE} - This query parameter defines a list of resource fields that need to be excluded

   * from the representation. The value of the header shall be a comma separated list of field names which need to be

   * excluded.

   * </ol>

   * <ol>

   * {@link QueryParameters#INCLUDE} - This query parameter defines a list of resource fields that will be selectively

   * included in the representation, fields from the default resource representation which are not listed here will be

   * excluded.

   * </ol>

   * </ul>

   .....

   */

  @GET

  @Path("{bookId}")

  public Response getBook(@PathParam("bookId") long bookId) {

    // get Representation constraints

    RepresentationConstraints constraints = getRepresentationConstraints();

    try {

      // get book, check if exists

      Book book = findBook(bookId);

      // initialize book resource fields, build response

      ResponseBuilder responseBuilder = Response.ok(BookResourceFactory.getBookResource(book, constraints));

      // add header for constraints of there are any

      constraints.toHttpHeaders(responseBuilder);

      return responseBuilder.build();

    } finally {

      // release the constraints

      constraints.release();

    }

  }

  //extracts and parses the representation constraints from the injected HttpServletRequest instance

  private RepresentationConstraints getRepresentationConstraints() throws WebApplicationException {

    try {

      return RepresentationConstraints.get(servletRequest);

    } catch (InvalidSyntaxException ise) {

      ErrorDescriptionUtils.throwWebApplicationException(HttpURLConnection.HTTP_BAD_REQUEST,

          GeneralErrorCodes.INVALID_REPRESENTATION_CONSTRAINTS_SYNTAX,

          "Representation constraints expression has invalid syntax : " + ise.getMessage(), null,

          null, -1, ise);

      return null;

    }

  }

  .....

}