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https://issues.apache.org/jira/browse/SOLR-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13144494#comment-13144494
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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|http://java.sun.com/j2ee/tutorial/1_3-fcs/examples/src/web/bookstore1/filters/CharResponseWrapper.java]
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 all.
> Regression in SolrDispatchFilter.java concerning the getOutputStream vs
> getWriter
> ---------------------------------------------------------------------------------
>
> Key: SOLR-2878
> URL: https://issues.apache.org/jira/browse/SOLR-2878
> 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 :
> {code:title=solrDispatchFilter.java|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
> {code:title=solrDispatchFilter.java|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
> {code:title=solrCustomFilter.java|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 out
> 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
> https://svn.apache.org/repos/asf/lucene/solr/branches/branch-1.4/src/webapp/src/org/apache/solr/servlet/SolrDispatchFilter.java
> Solr 3.4
> https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_3_4/solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java
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