The doFilter method of the Filter is called by the container
each time a request/response pair is passed through the chain due
to a client request for a resource at the end of the chain.
The FilterChain passed into this method allows the Filter to pass on the
request and response to the next entity in the chain.
This method first examines the request to check whether the client support
compression.
It simply just pass the request and response if there is no support for
compression.
If the compression support is available, it creates a
CompressionServletResponseWrapper object which compresses the content and
modifies the header if the content length is big enough.
It then invokes the next entity in the chain using the FilterChain object
(chain.doFilter()),
if (debug > 0) {
System.out.println("@doFilter");
}
if (compressionThreshold == 0) {
if (debug > 0) {
System.out.println("doFilter gets called, but compressionTreshold is set to 0 - no compression");
}
chain.doFilter(request, response);
return;
}
boolean supportCompression = false;
if (request instanceof HttpServletRequest) {
if (debug > 1) {
System.out.println("requestURI = " + ((HttpServletRequest)request).getRequestURI());
}
// Are we allowed to compress ?
String s = (String) ((HttpServletRequest)request).getParameter("gzip");
if ("false".equals(s)) {
if (debug > 0) {
System.out.println("got parameter gzip=false --> don't compress, just chain filter");
}
chain.doFilter(request, response);
return;
}
Enumeration e =
((HttpServletRequest)request).getHeaders("Accept-Encoding");
while (e.hasMoreElements()) {
String name = (String)e.nextElement();
if (name.indexOf("gzip") != -1) {
if (debug > 0) {
System.out.println("supports compression");
}
supportCompression = true;
} else {
if (debug > 0) {
System.out.println("no support for compresion");
}
}
}
}
if (!supportCompression) {
if (debug > 0) {
System.out.println("doFilter gets called wo compression");
}
chain.doFilter(request, response);
return;
} else {
if (response instanceof HttpServletResponse) {
CompressionServletResponseWrapper wrappedResponse =
new CompressionServletResponseWrapper((HttpServletResponse)response);
wrappedResponse.setDebugLevel(debug);
wrappedResponse.setCompressionThreshold(compressionThreshold);
if (debug > 0) {
System.out.println("doFilter gets called with compression");
}
try {
chain.doFilter(request, wrappedResponse);
} finally {
wrappedResponse.finishResponse();
}
return;
}
}
