package <%=packageName%>.web.filter.gzip;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;
public class GZipServletFilter implements Filter {
private Logger log = LoggerFactory.getLogger(GZipServletFilter.class);
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// Nothing to initialize
}
@Override
public void destroy() {
// Nothing to destroy
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpRequest = (HttpServletRequest) request;
HttpServletResponse httpResponse = (HttpServletResponse) response;
if (!isIncluded(httpRequest) && acceptsGZipEncoding(httpRequest) && !response.isCommitted()) {
// Client accepts zipped content
if (log.isTraceEnabled()) {
log.trace("{} Written with gzip compression", httpRequest.getRequestURL());
}
// Create a gzip stream
final ByteArrayOutputStream compressed = new ByteArrayOutputStream();
final GZIPOutputStream gzout = new GZIPOutputStream(compressed);
// Handle the request
final GZipServletResponseWrapper wrapper = new GZipServletResponseWrapper(httpResponse, gzout);
wrapper.setDisableFlushBuffer(true);
chain.doFilter(request, wrapper);
wrapper.flush();
gzout.close();
// double check one more time before writing out
// repsonse might have been committed due to error
if (response.isCommitted()) {
return;
}
// return on these special cases when content is empty or unchanged
switch (wrapper.getStatus()) {
case HttpServletResponse.SC_NO_CONTENT:
case HttpServletResponse.SC_RESET_CONTENT:
case HttpServletResponse.SC_NOT_MODIFIED:
return;
default:
}
// Saneness checks
byte[] compressedBytes = compressed.toByteArray();
boolean shouldGzippedBodyBeZero = GZipResponseUtil.shouldGzippedBodyBeZero(compressedBytes, httpRequest);
boolean shouldBodyBeZero = GZipResponseUtil.shouldBodyBeZero(httpRequest, wrapper.getStatus());
if (shouldGzippedBodyBeZero || shouldBodyBeZero) {
// No reason to add GZIP headers or write body if no content was written or status code specifies no
// content
response.setContentLength(0);
return;
}
// Write the zipped body
GZipResponseUtil.addGzipHeader(httpResponse);
response.setContentLength(compressedBytes.length);
response.getOutputStream().write(compressedBytes);
} else {
// Client does not accept zipped content - don't bother zipping
if (log.isTraceEnabled()) {
log.trace("{} Written without gzip compression because the request does not accept gzip", httpRequest.getRequestURL());
}
chain.doFilter(request, response);
}
}
/**
* Checks if the request uri is an include. These cannot be gzipped.
*/
private boolean isIncluded(final HttpServletRequest request) {
final String uri = (String) request.getAttribute("javax.servlet.include.request_uri");
final boolean includeRequest = !(uri == null);
if (includeRequest && log.isDebugEnabled()) {
log.debug("{} resulted in an include request. This is unusable, because"
+ "the response will be assembled into the overrall response. Not gzipping.",
request.getRequestURL());
}
return includeRequest;
}
private boolean acceptsGZipEncoding(HttpServletRequest httpRequest) {
String acceptEncoding = httpRequest.getHeader("Accept-Encoding");
return acceptEncoding != null && acceptEncoding.contains("gzip");
}
}