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From "Hoss Man (Commented) (JIRA)" <>
Subject [jira] [Commented] (SOLR-2878) Regression in concerning the getOutputStream vs getWriter
Date Sat, 05 Nov 2011 00:51:51 GMT


Hoss Man commented on SOLR-2878:

I think you are missunderstanding the problem -- i don't think it has anything to do with
the "flush" call.

in Solr 1.4, response.getWriter() was used by the SolrDispatchFilter for any character based
responses -- but in Solr 3.4, because of the issues related to SOLR-2381, SolrDispatchFilter
was modified to use response.getOutputStream() for both binary and character based streams.

If you have your own Filter that wraps the HttpServletResponse in something named "CharResponseWrapper"
(which i assume by the name is similar to [this example|]
that poped up when i searched for it)  then you are probably not ever wrapping/buffering the
OutputStream -- you are just wrapping a Writer that is never used -- so the Output written
to by the SOlrDispatchFilter is going straight back to the client.

FWIW: if you just want to add some headers to the response, and those headers don't depend
on the output of the SolrDispatchFilter, you should be able to set them on the response prior
to calling chain.doFilter, and then you don't have to worry about wrapping the response at
> Regression in concerning the getOutputStream vs getWriter
> ---------------------------------------------------------------------------------
>                 Key: SOLR-2878
>                 URL:
>             Project: Solr
>          Issue Type: Bug
>          Components: Build, Response Writers
>    Affects Versions: 3.4
>         Environment: Any unix system, it's a  global problem
>            Reporter: Nick Veenhof
>              Labels: filter, getOutputStream, getWriter, regression
>             Fix For: 3.5, 4.0
> In solr 1.4 we used getWriter in the writeResponse for solrDispatchFilter::doFilter which
invoked writeResponse.
> This code looked in summary like this :
> {|borderStyle=solid}
> private void writeResponse(SolrQueryResponse solrRsp, ServletResponse response, 
>    QueryResponseWriter responseWriter, SolrQueryRequest solrReq, Method reqMethod) 
>    throws IOException {
> ...
>  PrintWriter out = response.getWriter();
>  responseWriter.write(out, solrReq, solrRsp);
> ...
> {code}
> In solr 3.x this has changed to something like this 
> {|borderStyle=solid}
> private void writeResponse(SolrQueryResponse solrRsp, ServletResponse response,
>   QueryResponseWriter responseWriter, SolrQueryRequest solrReq, Method reqMethod) 
>   throws IOException {
> ...
> String charset = ContentStreamBase.getCharsetFromContentType(ct);
> Writer out = (charset == null || charset.equalsIgnoreCase("UTF-8"))
>   ? new OutputStreamWriter(response.getOutputStream(), UTF8)
>   : new OutputStreamWriter(response.getOutputStream(), charset);
> out = new FastWriter(out);
> responseWriter.write(out, solrReq, solrRsp);
> out.flush();
> ...
> {code}
> Now, when we add another filter that tries to modify the output it is being blocked by
the out.flush(). 
> flush() is telling our outputstream that it can write directly to the destination (similar
to the out.close()), since this normally happens automatically there shouldn't be a need to
execute this flush.
> In our case this secondary filter is trying to add headers to the response object. When
we were using getwriter() it was not closing the writer so we could still modify this output.
Since the flush happens now we are no longer able to modify the headers accordingly. 
> It would be an easy fix if the flush could be commented out and everything would work
but that is not the case. The headers are working when this happens but there is no more output.
> When I modify both classes to use getWriter() everything is working as expected.
> This is a severe regression for our use of solr.
> Our code that is used in the filter
> {|borderStyle=solid}
> public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) 
>   throws IOException, ServletException {
> ...
> Writer out = new OutputStreamWriter(response.getOutputStream(), "UTF8"); //auto flush
> out = new FastWriter(out);
> // convert to a chartext
> CharResponseWrapper wrapper = new CharResponseWrapper((HttpServletResponse) response);
> chain.doFilter(request, wrapper);
> String responseBody = wrapper.toString();
> //write the outgoing header. Only succeeds when flush of solrDispatchFilter is commented
> response.addHeader("pragma", "somevalue;");
> out.write(responseBody);
> ...
> {code}
> Sources :
> {quote}
> SRV.5.5 Closure of Response Object
> When a response is closed, the container must immediately flush all remaining content
in the response buffer to the client. The following events indicate that the servlet has satisfied
the request and that the response object is to be closed:
> • The termination of the service method of the servlet. 
> • The amount of content specified in the setContentLength method of the response has
been written to the response. 
> • The sendError method is called. 
> • The sendRedirect method is called.
> {quote}
> Solr 1.4
> Solr 3.4

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