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From "Nick Veenhof (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-2878) Regression in SolrDispatchFilter.java concerning the getOutputStream vs getWriter
Date Sat, 05 Nov 2011 08:28:51 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13144627#comment-13144627
] 

Nick Veenhof commented on SOLR-2878:
------------------------------------

After loads of research and figuring out why it happened I found a CharResponseWrapper that
worked for getOutputStream also.
For archiving purposes I'd like to put the full class here :

With this class it all seems to work as it did before. Thanks for the pointer on the CharResponseWrapper,
I was not deep enough in the java servlets world to understand that this CharResponseWrapper
could have such an impact on the response.

{code}
/**
 * 
 */
package clime.messadmin.filter;

import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * @author C&eacute;drik LIME
 */
class CharResponseWrapper extends HttpServletResponseWrapper {
	protected CharArrayWriter output;
	protected ServletOutputStream stream = null;
	protected PrintWriter writer = null;

	static class CharOutputStream extends ServletOutputStream {
		CharArrayWriter outstream;

		public CharOutputStream(CharArrayWriter out) {
			outstream = out;
		}

		/** {@inheritDoc} */
//	  @Override
		public void write(int b) {
			outstream.write(b);
		}
		public void write(String str) throws IOException {
			outstream.write(str);
		}
	}

	/** {@inheritDoc} */
//  @Override
	public String toString() {
		return output.toString();
	}

	public char[] toCharArray() {
		return (output.toCharArray());
	}

	public CharResponseWrapper(HttpServletResponse response) {
		super(response);
		output = new CharArrayWriter();
	}

	/** {@inheritDoc} */
//  @Override
	public synchronized PrintWriter getWriter() {
		if (stream != null) {
			throw new IllegalStateException("getOutputStream() has already been called for this response");
		}
		if (writer == null) {
			writer = new PrintWriter(output);
		}
		return writer;
	}

	/** {@inheritDoc} */
//  @Override
	public synchronized ServletOutputStream getOutputStream() {
		if (writer != null) {
			throw new IllegalStateException("getWriter() has already been called for this response");
		}
		if (stream == null) {
			stream = new CharOutputStream(output);
		}
		return stream;
	}

}
{code}
                
> 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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