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From David Hosier <hosier.da...@me.com>
Subject Re: Broken BasicResponseHandler
Date Thu, 06 Oct 2011 21:23:01 GMT
On Thursday, October 6, 2011 at 1:40 PM, Oleg Kalnichevski wrote:
> On Thu, 2011-10-06 at 13:21 -0700, David Hosier wrote:
> > Understood. The library does not support the use case of obtaining the entity of
a response via the recommended usage for any response other than a 2xx.
> 
> BasicResponseHandler does not, hence, unsurprisingly, the name Basic.
> However, there is _nothing_ that prevents you from writing a custom,
> better ResponseHandler which handles response entities differently.
> While the ResponseHandler interface is indeed the recommended way of
> handling responses, the BasicResponseHandler is just its very basic
> implementation which was never meant to be used for anything else but
> the most simplistic use cases. No one in their sane mind should _ever_
> convert an HTTP response to a string in a productive application. 
> 
> >  Additionally, the javadoc for BasicResponseHandler is incorrect. 
> 
> What exactly is incorrect? If you think javadocs are not clear enough or
> specific enough I'll happily apply a patch if you submit one.
I went and looked more closely, and the issue is that I was looking at the class-level javadoc
for BasicResponseHandler. The class-level javadoc indicates that the response body is read
before throwing the exception on status codes >=300. However, the javadoc for the handleResponse()
method does not indicate that the response body is read. The statement about reading the response
body on >=300 really only occurs when used with HttpClient, and it's that class that actually
does the reading. That's how I read the code at least.
> 
> Oleg
> 
> > So now that I understand better how things work, I can take action accordingly.
Thanks for the responses.
> > 
> > -- David Hosier
> > 
> > On Thursday, October 6, 2011 at 11:40 AM, Oleg Kalnichevski wrote:
> > 
> > > On Thu, 2011-10-06 at 11:31 -0700, David Hosier wrote:
> > > > I'm using the DefaultHttpClient to make the call, yes. I want to use DefaultHttpClient
with the ResponseHandler the way I am supposed to. However, the API does not give me the ability
to get a hold of the Entity if the status code is 404, because it throws an Exception which
does not contain the entity value. I need the Entity value, even if the call returns 404.
As far as I can tell, I cannot get the information I need from the API the way it is designed
to be used. Is that clearer? Is my assessment correct?
> > > 
> > > Yes, it is intentional that the exception thrown does not contain a
> > > response body, because it would involve reading the entire body content
> > > into a memory buffer.
> > > 
> > > Oleg
> > > 
> > > 
> > > > -- David Hosier
> > > > 
> > > > On Thursday, October 6, 2011 at 11:29 AM, Oleg Kalnichevski wrote:
> > > > 
> > > > > On Thu, 2011-10-06 at 10:47 -0700, David Hosier wrote:
> > > > > > I am using this to interface with some REST services. One key
to a good REST service is to never let something like a 404 spit out the server's generic
404 HTML page in response to a REST request. So my service instead returns an entity with
the 404 that says something like "Could not find alert 12334". I should be able to show this
response entity. However, given the way the ResponseHandler works with HttpClient, this is
not possible, because the entity is not part of the Exception that is thrown when the ResponseHandler
encounters a 404. Without manually reading the entity after ResponseHandler throws an Exception,
I would only be able to show the fields that are contained in the Exception. That means I
could only show the text 'Not Found', which is hardly meaningful since the status code of
404 already tells me that.
> > > > > 
> > > > > You are using ResponseHandler to interface with some REST services
> > > > > without using DefaultHttpClient? I am sorry but it still makes no
sense
> > > > > to me. You might as well handle responses from that service _any_
way
> > > > > you like without using a ResponseHandler.
> > > > > 
> > > > > Oleg
> > > > > 
> > > > > > -- David Hosier
> > > > > > 
> > > > > > On Thursday, October 6, 2011 at 5:39 AM, Oleg Kalnichevski wrote:
> > > > > > 
> > > > > > > On Thu, 2011-10-06 at 02:59 -0700, David Hosier wrote:
> > > > > > > > Ok, I see what the difference is in this situation.
I am not passing the ResponseHandler to the execute() method. I am actually calling handleResponse()
on the ResponseHandler manually.
> > > > > > > 
> > > > > > > I honestly see no sense in doing so. ResponseHandler is
pretty much
> > > > > > > useless without the resource management code in AbstractHttpClient.
> > > > > > > 
> > > > > > > What is the reason you want to invoke #handleResponse manually?
> > > > > > > 
> > > > > > > Oleg
> > > > > > > 
> > > > > > > >  The problem I have with the implementation is that
I return error messages on error conditions. With the way this works, you can only get very
basic information from the HttpResponseException. For example, on a 404, it looks like the
Exception only contains 404 and 'Not Found'. I am able to pluck out the entity when invoking
handleResponse() manually by simply consuming the entity myself, but it's not possible to
get the entity if the ResponseHandler is passed to execute() and the status is not 2xx. Am
I off base here or is my analysis correct? Would you recommend that if I really need the entity
on a non-2xx response that I just keep manually consuming the entity? I'm not sure it would
make sense for your library to attempt to consume the entity in BasicResponseHandler and try
to add it as an
> > > > > > > >  other fi
> > > > > > > > eld to the HttpResponseException. The AbstractHttpClient
code you linked me to would have to change if you did that.
> > > > > > > > 
> > > > > > > > -- David Hosier
> > > > > > > > 
> > > > > > > > On Thursday, October 6, 2011 at 2:30 AM, David Hosier
wrote:
> > > > > > > > 
> > > > > > > > > On Thursday, October 6, 2011 at 2:22 AM, Oleg
Kalnichevski wrote:
> > > > > > > > > > On Wed, 2011-10-05 at 13:44 -0700, David
Hosier wrote:
> > > > > > > > > > > Perhaps I'm wrong, but the code for
BasicResponseHandler in httpclient 4.1.2 does not satisfy the javadocs as written. The javadoc
states the following:
> > > > > > > > > > > 
> > > > > > > > > > > "If the response code was >= 300,
the response body is consumed and an HttpResponseException (http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/HttpResponseException.html)
is thrown."
> > > > > > > > > > > 
> > > > > > > > > > > However, the code does not do that:
> > > > > > > > > > > 
> > > > > > > > > > > StatusLine statusLine = response.getStatusLine();
> > > > > > > > > > > if (statusLine.getStatusCode() >=
300) {
> > > > > > > > > > >  throw new HttpResponseException(statusLine.getStatusCode(),
> > > > > > > > > > >  statusLine.getReasonPhrase());
> > > > > > > > > > > }
> > > > > > > > > > > 
> > > > > > > > > > > HttpEntity entity = response.getEntity();
> > > > > > > > > > > return entity == null ? null : EntityUtils.toString(entity);
> > > > > > > > > > > 
> > > > > > > > > > > The code clearly throws the Exception
without reading the entity. So what happens is that if you get a non-2xx response, connections
are never released as can be seen by enabling DEBUG logging for the library. Am I misreading
the code or javadocs, or is this really broken? If I catch the Exception and then read the
entity manually like shown above, I can see the connections being closed.
> > > > > > > > > > > 
> > > > > > > > > > > -David
> > > > > > > > > > 
> > > > > > > > > > Hi David
> > > > > > > > > > The resource management is taken care of
by HttpClient [1]. I do not
> > > > > > > > > > think BasicResponseHandler is broken. The
whole point of ResponseHandler
> > > > > > > > > > is to free the user from having to worry
about resource management and
> > > > > > > > > > response entities.
> > > > > > > > > Interesting. Thanks for the link to the code.
I can assure you that in my situation however, that the connections are not getting closed.
I'll take a closer look at the code and compare it to this linked code to see if I'm using
the right stuff. My assumption at this point then is that I'm just doing something wrong.
Thanks. 
> > > > > > > > > > 
> > > > > > > > > > Oleg
> > > > > > > > > > 
> > > > > > > > > > [1]
> > > > > > > > > > http://hc.apache.org/httpcomponents-client-ga/httpclient/xref/org/apache/http/impl/client/AbstractHttpClient.html#930
> > > > > > > > > > 
> > > > > > > > > > 
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