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https://issues.apache.org/jira/browse/SOLR-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13144648#comment-13144648
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Uwe Schindler commented on SOLR-2878:
-------------------------------------
Just to add another note:
The API of ServletResponse supplying getWriter() APIs is a mis-conception in
relation to the HTTP protocol. The HTTP protocol is defined to transfer binary
output. The use of a char stream as Java supplies by getWriter() is only for
convenience, but a filter should never rely on the fact that a Servlet uses a
Writer. Unfortunately Sun never changed this for backwards compatibility
reasons, but the correct API design of the Servlet API would be to make the
getWriter() method final in the ServletResponse.
About your last example code that works around your issue: The code of your
filter is simply wrong - it assumes that all chars are represented by exactly
one byte with the same binary code-point in the output, which is only true for
US-ASCII. It completely ignores the charset. Solr by default always uses UTF-8
so you would make the output unreadable once a code poiunt > 127 would appear
in the output. To correctly buffer your output use a ByteArrayOutputStream. To
check the contents of the buffered code as a string, you have to use: new
String(ByteArrayOutputStream.getBytes(),
ServletResponse.getCharacterEncoding());
> 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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