gzip压缩
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在web.xml中的配置: 类GZIPResponseStream:
<filter-name>compressionFilter</filter-name>
<filter-class>org.xblogx.base.GZIPFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>compressionFilter</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
类GZIPFilter
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.displaytag.tags.TableTagParameters;
import org.springframework.web.filter.OncePerRequestFilter;
public class GZIPFilter extends OncePerRequestFilter {
private final transient Log log = LogFactory.getLog(GZIPFilter.class);
public void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
FilterChain chain)
throws IOException, ServletException {
if (isGZIPSupported(request)) {
if (log.isDebugEnabled()) {
log.debug("GZIP supported, compressing response");
}
GZIPResponseWrapper wrappedResponse =
new GZIPResponseWrapper(response);
chain.doFilter(request, wrappedResponse);
wrappedResponse.finishResponse();
return;
}
chain.doFilter(request, response);
}
/**
* Convenience method to test for GZIP cababilities
* @param req The current user request
* @return boolean indicating GZIP support
*/
private boolean isGZIPSupported(HttpServletRequest req) {
// disable gzip filter for exporting from displaytag
String exporting = req.getParameter(TableTagParameters.PARAMETER_EXPORTING);
if (exporting != null) {
log.debug("detected excel export, disabling filter...");
return false;
}
String browserEncodings = req.getHeader("accept-encoding");
boolean supported = ((browserEncodings != null) &&
(browserEncodings.indexOf("gzip") != -1));
String userAgent = req.getHeader("user-agent");
if ((userAgent != null) && userAgent.startsWith("httpunit")) {
log.debug("httpunit detected, disabling filter...");
return false;
} else {
return supported;
}
}
}
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPOutputStream;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
/**
* Wraps Response Stream for GZipFilter
*
* @author Matt Raible
* @version $Revision: 1.3 $ $Date: 2004-05-15 20:18:10 -0600 (Sat, 15 May 2004) $
*/
public class GZIPResponseStream extends ServletOutputStream {
// abstraction of the output stream used for compression
protected OutputStream bufferedOutput = null;
// state keeping variable for if close() has been called
protected boolean closed = false;
// reference to original response
protected HttpServletResponse response = null;
// reference to the output stream to the client's browser
protected ServletOutputStream output = null;
// default size of the in-memory buffer
private int bufferSize = 50000;
public GZIPResponseStream(HttpServletResponse response)
throws IOException {
super();
closed = false;
this.response = response;
this.output = response.getOutputStream();
bufferedOutput = new ByteArrayOutputStream();
}
public void close() throws IOException {
// verify the stream is yet to be closed
if (closed) {
throw new IOException("This output stream has already been closed");
}
// if we buffered everything in memory, gzip it
if (bufferedOutput instanceof ByteArrayOutputStream) {
// get the content
ByteArrayOutputStream baos = (ByteArrayOutputStream) bufferedOutput;
// prepare a gzip stream
ByteArrayOutputStream compressedContent =
new ByteArrayOutputStream();
GZIPOutputStream gzipstream =
new GZIPOutputStream(compressedContent);
byte[] bytes = baos.toByteArray();
gzipstream.write(bytes);
gzipstream.finish();
// get the compressed content
byte[] compressedBytes = compressedContent.toByteArray();
// set appropriate HTTP headers
response.setContentLength(compressedBytes.length);
response.addHeader("Content-Encoding", "gzip");
output.write(compressedBytes);
output.flush();
output.close();
closed = true;
}
// if things were not buffered in memory, finish the GZIP stream and response
else if (bufferedOutput instanceof GZIPOutputStream) {
// cast to appropriate type
GZIPOutputStream gzipstream = (GZIPOutputStream) bufferedOutput;
// finish the compression
gzipstream.finish();
// finish the response
output.flush();
output.close();
closed = true;
}
}
public void flush() throws IOException {
if (closed) {
throw new IOException("Cannot flush a closed output stream");
}
bufferedOutput.flush();
}
public void write(int b) throws IOException {
if (closed) {
throw new IOException("Cannot write to a closed output stream");
}
// make sure we aren't over the buffer's limit
checkBufferSize(1);
// write the byte to the temporary output
bufferedOutput.write((byte) b);
}
private void checkBufferSize(int length) throws IOException {
// check if we are buffering too large of a file
if (bufferedOutput instanceof ByteArrayOutputStream) {
ByteArrayOutputStream baos = (ByteArrayOutputStream) bufferedOutput;
if ((baos.size() + length) > bufferSize) {
// files too large to keep in memory are sent to the client without Content-Length specified
response.addHeader("Content-Encoding", "gzip");
// get existing bytes
byte[] bytes = baos.toByteArray();
// make new gzip stream using the response output stream
GZIPOutputStream gzipstream = new GZIPOutputStream(output);
gzipstream.write(bytes);
// we are no longer buffering, send content via gzipstream
bufferedOutput = gzipstream;
}
}
}
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
public void write(byte[] b, int off, int len) throws IOException {
if (closed) {
throw new IOException("Cannot write to a closed output stream");
}
// make sure we aren't over the buffer's limit
checkBufferSize(len);
// write the content to the buffer
bufferedOutput.write(b, off, len);
}
public boolean closed() {
return (this.closed);
}
public void reset() {
//noop
}
}
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* Wraps Response for GZipFilter
*
* @author Matt Raible, cmurphy@intechtual.com
*/
public class GZIPResponseWrapper extends HttpServletResponseWrapper {
private transient final Log log = LogFactory.getLog(GZIPResponseWrapper.class);
protected HttpServletResponse origResponse = null;
protected ServletOutputStream stream = null;
protected PrintWriter writer = null;
protected int error = 0;
public GZIPResponseWrapper(HttpServletResponse response) {
super(response);
origResponse = response;
}
public ServletOutputStream createOutputStream() throws IOException {
return (new GZIPResponseStream(origResponse));
}
public void finishResponse() {
try {
if (writer != null) {
writer.close();
} else {
if (stream != null) {
stream.close();
}
}
} catch (IOException e) {
}
}
public void flushBuffer() throws IOException {
if (stream != null) {
stream.flush();
}
}
public ServletOutputStream getOutputStream() throws IOException {
if (writer != null) {
throw new IllegalStateException("getWriter() has already been called!");
}
if (stream == null) {
stream = createOutputStream();
}
return (stream);
}
public PrintWriter getWriter() throws IOException {
// From cmurphy@intechtual.com to fix:
// https://appfuse.dev.java.net/issues/show_bug.cgi?id=59
if (this.origResponse != null && this.origResponse.isCommitted()) {
return super.getWriter();
}
if (writer != null) {
return (writer);
}
if (stream != null) {
throw new IllegalStateException("getOutputStream() has already been called!");
}
stream = createOutputStream();
writer =
new PrintWriter(new OutputStreamWriter(stream,
origResponse.getCharacterEncoding()));
return (writer);
}
public void setContentLength(int length) {
}
/**
* @see javax.servlet.http.HttpServletResponse#sendError(int, java.lang.String)
*/
public void sendError(int error, String message) throws IOException {
super.sendError(error, message);
this.error = error;
if (log.isDebugEnabled()) {
log.debug("sending error: " + error + " [" + message + "]");
}
}
}
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