[jax-rs-spec users] [jsr339-experts] Re: Re: Unexpected Response.fromResponse result

From: Santiago Pericas-Geertsen <>
Date: Tue, 7 Aug 2012 10:02:36 -0400

On Aug 7, 2012, at 3:49 AM, Sergey Beryozkin wrote:

> On 07/08/12 16:15, Bill Burke wrote:
>> I don't understand what the problem is. Javadoc is just saying that if
>> the underlying entity is an InputStream, then the Response copy has a
>> reference to that InputStream. You probalby should buffer it because you
>> will get an error if two different Response objects referencing the same
>> InputStream call readEntity().
> Actually, there are few problems here.
> 1. Response entity of the type like String or some other type different from InputStream is lost during Response.fromResponse;

 So you think there's a problem in the code, not the Javadoc, right? Here are the first few lines of that method:

    public static ResponseBuilder fromResponse(Response response) {
        ResponseBuilder b = status(response.getStatus());
        if (response.hasEntity()) {

 It seems OK to me, but there could a problem elsewhere.

> 2. The whole idea of the user having to do 'buffer' for Response.fromResponse to work properly is an anti-pattern. It's not the responsibility of the calling code.

 It think this is a consequence of the shallow copying semantics above. Often a trade-off between performance and usability.

-- Santiago

>> On 8/6/2012 1:10 PM, Sergey Beryozkin wrote:
>>> In JAX-RS 1.1 I was seeing an easy to understand Response.fromResponse
>>> output. For example,
>>> Response r = Response.entity("Hello").build();
>>> Response r2 = Response.fromResponse(r);
>>> assertSame("Hello", r2.getEntity());
>>> Note that 'r' contains a String, not 'InputStream'.
>>> 'Response.entity("Hello").build()' is executed on the server, where as
>>> 'Response.fromResponse(r)' is a follow up operation executed in a
>>> response filter.
>>> In 2.0 I'm seeing 'Response.fromResponse(r)' losing the original
>>> 'String', and after checking the java docs I'm seeing:
>>> "Note that if the entity is backed by an un-consumed input stream, the
>>> reference to the stream is copied. In such case make sure to buffer the
>>> entity stream of the original response instance before passing it to
>>> this method."
>>> I think it's an API bug. The assumption is made there that the Response
>>> entity is kept as InputStream - which is an implementation detail of
>>> Response. I've been saying that all this buffer() stuff is out of scope
>>> of Response but failed to get anyone convinced.
>>> For the very least, the javadocs quoted above should further clarify
>>> that it only applies to the client side where it is reasonable to expect
>>> Response contains InputStream originally.
>>> Any comments ?
>>> Sergey