com.mirantis.cachemod.filter.CacheFilter.java Source code

Introduction

Here is the source code for com.mirantis.cachemod.filter.CacheFilter.java

Source

/*
 * Copyright 2011 Mirantis Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mirantis.cachemod.filter;

import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.OutputStream;

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;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * A cache filter for web requests.
 *
 * @author aschwid@mirantis.com (Alex Schwid)
 */
public class CacheFilter implements Filter {

    private static final Log log = LogFactory.getLog(CacheFilter.class);

    private CacheConfiguration conf = null;

    public void destroy() {
    }

    private boolean isCacheable(ServletRequest request) {
        if (request instanceof HttpServletRequest) {
            HttpServletRequest httpRequest = (HttpServletRequest) request;
            if (conf.getEscapeMethods().contains(httpRequest.getMethod())) {
                return false;
            }
            if (conf.isEscapeSessionId() && httpRequest.isRequestedSessionIdFromURL()) {
                return false;
            }
        }
        return true;
    }

    public boolean isFragment(HttpServletRequest request) {

        switch (conf.getFragment()) {
        case AUTO:
            return request.getAttribute("javax.servlet.include.request_uri") != null;
        case NO:
            return false;
        case YES:
            return true;
        }

        return request.getAttribute("javax.servlet.include.request_uri") != null;
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws ServletException, IOException {

        if (request.getAttribute(conf.getAlreadyFilteredKey()) != null || !isCacheable(request)) {

            /*
             *  This request is not Cacheable
             */

            chain.doFilter(request, response);
        } else {
            request.setAttribute(conf.getAlreadyFilteredKey(), Boolean.TRUE);

            HttpServletRequest httpRequest = (HttpServletRequest) request;
            boolean fragmentRequest = isFragment(httpRequest);

            String key = conf.getCacheKeyProvider().createKey(httpRequest);

            CacheEntry cacheEntry = conf.getCacheProvider().getEntry(key);
            if (cacheEntry != null) {

                if (!fragmentRequest) {

                    /*
                     * -1 of no in header
                     */
                    long clientLastModified = httpRequest.getDateHeader("If-Modified-Since");

                    /*
                     * Reply with SC_NOT_MODIFIED for client that has newest page 
                     */
                    if ((clientLastModified != -1) && (clientLastModified >= cacheEntry.getLastModified())) {
                        ((HttpServletResponse) response).setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                        return;
                    }
                }

                writeCacheToResponse(cacheEntry, response, fragmentRequest);

            } else {
                cacheEntry = conf.getCacheProvider().instantiateEntry();

                CacheHttpServletResponse cacheResponse = new CacheHttpServletResponse(
                        (HttpServletResponse) response, cacheEntry, conf, fragmentRequest);
                chain.doFilter(request, cacheResponse);

                if (cacheResponse.getStatus() == HttpServletResponse.SC_OK) {
                    cacheResponse.commit();
                    if (conf.getUserDataProvider() != null) {
                        cacheEntry.setUserData(conf.getUserDataProvider().createUserData(httpRequest));
                    }
                    conf.getCacheProvider().putEntry(key, cacheEntry);
                }
            }
        }

    }

    public void writeCacheToResponse(CacheEntry cacheEntry, ServletResponse response, boolean fragment)
            throws IOException {

        if (cacheEntry.getContentType() != null) {
            response.setContentType(cacheEntry.getContentType());
        }

        if (!fragment) {

            if (response instanceof HttpServletResponse) {
                HttpServletResponse httpResponse = (HttpServletResponse) response;

                if (cacheEntry.getLastModified() != -1) {
                    httpResponse.setDateHeader("Last-Modified", cacheEntry.getLastModified());
                }

                if (cacheEntry.getExpires() != Long.MAX_VALUE) {
                    httpResponse.setDateHeader("Expires", cacheEntry.getExpires());
                }

                if (cacheEntry.getMaxAge() != -1) {
                    if (cacheEntry.getMaxAge() < 0) { // set max-age based on life time
                        long currentMaxAge = -cacheEntry.getMaxAge() / 1000 - System.currentTimeMillis() / 1000;
                        if (currentMaxAge < 0) {
                            currentMaxAge = 0;
                        }
                        httpResponse.addHeader("Cache-Control", "max-age=" + currentMaxAge);
                    } else {
                        httpResponse.addHeader("Cache-Control", "max-age=" + cacheEntry.getMaxAge());
                    }
                }

            }
        }

        if (cacheEntry.getLocale() != null) {
            response.setLocale(cacheEntry.getLocale());
        }

        OutputStream out = new BufferedOutputStream(response.getOutputStream());
        response.setContentLength(cacheEntry.getContent().length);
        out.write(cacheEntry.getContent());
        out.flush();
    }

    public void init(FilterConfig config) {
        conf = new CacheConfiguration(config);

        log.info("CacheFilter: Filter starting. " + conf.toString());
        conf.getCacheProvider().init(conf.getCacheName());

        if (conf.getUserDataProvider() != null) {
            conf.getUserDataProvider().createIndexes(conf.getCacheProvider().getCache());
        }
    }

}