compressionfilter.java

struts_spring_hibernate开发实例

/*
 * CompressionFilter.java
 * $Header: /home/cvs/jakarta-tomcat-4.0/webapps/examples/WEB-INF/classes/compressionFilters/CompressionFilter.java,v 1.8 2002/07/16 17:19:13 amyroh Exp $
 * $Revision: 1.8 $
 * $Date: 2002/07/16 17:19:13 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */
package jaoso.framework.web.filter.compression;

import java.io.IOException;

import java.util.Enumeration;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Implementation of <code>javax.servlet.Filter</code> used to compress the
 * ServletResponse if it is bigger than a threshold.
 * 
 * @author Amy Roh
 * @author Dmitri Valdin
 * @version $Revision: 1.8 $, $Date: 2002/07/16 17:19:13 $
 */
public class CompressionFilter implements Filter {
	/**
	 * The filter configuration object we are associated with. If this value is
	 * null, this filter instance is not currently configured.
	 */
	private FilterConfig config = null;

	/**
	 * Minimal reasonable threshold
	 */
	private int minThreshold = 128;

	/**
	 * The threshold number to compress
	 */
	protected int compressionThreshold;

	/**
	 * Debug level for this filter
	 */
	private int debug = 0;

	/**
	 * Place this filter into service.
	 * 
	 * @param filterConfig
	 *            The filter configuration object
	 */
	public void init(FilterConfig filterConfig) {
		config = filterConfig;

		if (filterConfig != null) {
			String value = filterConfig.getInitParameter("debug");

			if (value != null) {
				debug = Integer.parseInt(value);
			} else {
				debug = 0;
			}

			String str = filterConfig.getInitParameter("compressionThreshold");

			if (str != null) {
				compressionThreshold = Integer.parseInt(str);

				if ((compressionThreshold != 0)
						&& (compressionThreshold < minThreshold)) {
					if (debug > 0) {
						System.out
								.println("compressionThreshold should be either 0 - no compression or >= "
										+ minThreshold);
						System.out.println("compressionThreshold set to "
								+ minThreshold);
					}

					compressionThreshold = minThreshold;
				}
			} else {
				compressionThreshold = 0;
			}
		} else {
			compressionThreshold = 0;
		}
	}

	/**
	 * Take this filter out of service.
	 */
	public void destroy() {
		this.config = null;
	}

	/**
	 * The <code>doFilter</code> 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.
	 * <p>
	 * This method first examines the request to check whether the client
	 * support compression. <br>
	 * It simply just pass the request and response if there is no support for
	 * compression. <br>
	 * 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 (
	 * <code>chain.doFilter()</code>),<br>
	 */
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		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;
			}
		}
	}

	/**
	 * Set filter config This function is equivalent to init. Required by
	 * Weblogic 6.1
	 * 
	 * @param filterConfig
	 *            The filter configuration object
	 */
	public void setFilterConfig(FilterConfig filterConfig) {
		init(filterConfig);
	}

	/**
	 * Return filter config Required by Weblogic 6.1
	 */
	public FilterConfig getFilterConfig() {
		return config;
	}
}