gzipencodefilter.java

来自「cwbbs 云网论坛源码」· Java 代码 · 共 122 行

package cn.js.fan.web;

import java.io.*;
import java.util.zip.GZIPOutputStream;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Enumeration;

public class GZIPEncodeFilter implements Filter {
    public void init(FilterConfig filterConfig) {}

    public void doFilter(ServletRequest request, ServletResponse response,
                         FilterChain chain) throws IOException,
            ServletException {
        String uri = ((HttpServletRequest) request).getRequestURI();
        if (Global.isGZIPEnabled) {
            if (uri.endsWith(".jsp") || uri.endsWith(".htm") ||
                uri.endsWith(".html")) { 
                String transferEncoding = getGZIPEncoding((HttpServletRequest)
                        request);
                
                

                if (transferEncoding == null) {
                    chain.doFilter(request, response);
                } else {
                    ((HttpServletResponse) response).setHeader(
                            "Content-Encoding",
                            transferEncoding);
                    GZIPEncodableResponse wrappedResponse = new
                            GZIPEncodableResponse((
                                    HttpServletResponse) response);
                    chain.doFilter(request, wrappedResponse);
                    wrappedResponse.flush();
                }
            }
            else
                chain.doFilter(request, response);
        }
        else
            chain.doFilter(request, response);
    }

    public void destroy() {}

    private static String getGZIPEncoding(HttpServletRequest request) {
        String acceptEncoding = request.getHeader("Accept-Encoding");
        
        if (acceptEncoding == null)
            return null;
        acceptEncoding = acceptEncoding.toLowerCase();
        if (acceptEncoding.indexOf("x-gzip") >= 0) {
            return "x-gzip";
        }
        if (acceptEncoding.indexOf("gzip") >= 0) {
            return "gzip";
        }
        return null;
    }

    private class GZIPEncodableResponse extends HttpServletResponseWrapper {
        private GZIPServletStream wrappedOut;
        public GZIPEncodableResponse(HttpServletResponse response) throws
                IOException {
            super(response);
            wrappedOut = new GZIPServletStream(response.getOutputStream());
        }

        public ServletOutputStream getOutputStream() throws IOException {
            return wrappedOut;
        }

        private PrintWriter wrappedWriter;
        public PrintWriter getWriter() throws IOException {
            if (wrappedWriter == null) {
                wrappedWriter = new PrintWriter(new OutputStreamWriter(
                        getOutputStream(), getCharacterEncoding()));
            }
            return wrappedWriter;
        }

        public void flush() throws IOException {
            if (wrappedWriter != null) {
                wrappedWriter.flush();
            }
            wrappedOut.finish();
        }
    }

    private class GZIPServletStream extends ServletOutputStream {
        private GZIPOutputStream outputStream;
        public GZIPServletStream(OutputStream source) throws IOException {
            outputStream = new GZIPOutputStream(source);
        }

        public void finish() throws IOException {
            outputStream.finish();
        }

        public void write(byte[] buf) throws IOException {
            outputStream.write(buf);
        }

        public void write(byte[] buf, int off, int len) throws IOException {
            outputStream.write(buf, off, len);
        }

        public void write(int c) throws IOException {
            outputStream.write(c);
        }

        public void flush() throws IOException {
            outputStream.flush();
        }

        public void close() throws IOException {
            outputStream.close();
        }
    }
}