@Override
  public Map<String, String> getResponseHeaders()
  {
    return Collections.unmodifiableSortedMap(_responseHeaders);
  }
@Test(expectedExceptions = UnsupportedOperationException.class)
  public void testUnmodifiableHeaders() throws RestLiSyntaxException
  {
    final ResourceContextImpl context = new ResourceContextImpl();
    context.getResponseHeaders().put(RestConstants.HEADER_ID, "foobar");
  }