/
OnDemandResponseBufferFilter.java
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/
OnDemandResponseBufferFilter.java
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/*
* Copyright OmniFaces
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.omnifaces.filter;
import java.io.IOException;
import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;
import org.omnifaces.component.output.Cache;
import org.omnifaces.servlet.BufferedHttpServletResponse;
/**
* Filter that wraps the response with one capable of buffering on command.
* <p>
* The response wrapper is additionally make available as a request attribute, so it's always obtainable even if a following filter
* wraps the response again. By default the response wrapper is in "pass-through" mode, meaning it will do no buffering. Anywhere during the
* request it can be switched to buffer by setting its <code>passThrough</code> argument to false.
* <p>
* The next call to obtain the response's writer will then provide one that buffers. Do note that any existing writer that has been obtained
* before <code>passThrough</code> was set to false and is used afterwards, will <b>not</b> automatically start buffering. Only newly obtained
* writers will buffer from that point on.
* <p>
* If at the end of the request, when this filter resumes control again, the response is still buffering (<code>passThrough</code> is false)
* its buffer will be automatically flushed to the underlying response. If however the buffer is not empty, but <code>passThrough</code> is true,
* no such flushing will be done and it's assumed the application has taken care of this.
*
* @author Arjan Tijms
* @since 1.2
* @see Cache
*/
public class OnDemandResponseBufferFilter extends HttpFilter {
/** The request attribute name under which the buffered response is stored. */
public static final String BUFFERED_RESPONSE = "org.omnifaces.servlet.BUFFERED_RESPONSE";
@Override
public void doFilter(HttpServletRequest request, HttpServletResponse response, HttpSession session, FilterChain chain) throws ServletException,
IOException {
BufferedHttpServletResponse bufferedResponse = new BufferedHttpServletResponse(response);
// By default don't buffer, code has to activate this explicitly.
bufferedResponse.setPassThrough(true);
request.setAttribute(BUFFERED_RESPONSE, bufferedResponse);
try {
chain.doFilter(request, bufferedResponse);
} finally {
if (!bufferedResponse.isPassThrough()) {
// TODO: output stream support
response.getWriter().write(bufferedResponse.getBufferAsString());
}
}
}
}