CacheFilter.java

/*
 * Copyright 2003 Jayson Falkner (jayson@jspinsider.com)
 * This code is from "Servlets and JavaServer pages; the J2EE Web Tier",
 * http://www.jspbook.com. You may freely use the code both commercially
 * and non-commercially. If you like the code, please pick up a copy of
 * the book and help support the authors, development of more free code,
 * and the JSP/Servlet/J2EE community.
 *
 * See http://www.onjava.com/pub/a/onjava/2003/11/19/filters.html
 */
package org.freehep.webutil.cache;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import org.freehep.webutil.cache.CacheResponseWrapper;

public class CacheFilter implements Filter {
  ServletContext sc;
  FilterConfig fc;
  long cacheTimeout = Long.MAX_VALUE;

  public void doFilter(ServletRequest req, ServletResponse res,
                       FilterChain chain)
                       throws IOException, ServletException {
    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) res;

    // check if was a resource that shouldn't be cached.
    String r = sc.getRealPath("");
    String path = fc.getInitParameter(request.getRequestURI());
    if (path!= null && path.equals("nocache")) {
      chain.doFilter(request, response);
      return;
    }
    path = r+path;

    // customize to match parameters
    String id = request.getRequestURI()+request.getQueryString();
    // optionally append i18n sensitivity
    String localeSensitive = fc.getInitParameter("locale-sensitive");
    if (localeSensitive != null) {
      StringWriter ldata = new StringWriter();
      Enumeration locales = request.getLocales();
      while (locales.hasMoreElements()) {
        Locale locale = (Locale)locales.nextElement();
        ldata.write(locale.getISO3Language());
      }
      id = id + ldata.toString();
    }
    File tempDir = (File)sc.getAttribute(
      "javax.servlet.context.tempdir");

    // get possible cache
    String temp = tempDir.getAbsolutePath();
    File file = new File(temp+id);

    // get current resource
    if (path == null) {
      path = sc.getRealPath(request.getRequestURI());
    }
    File current = new File(path);

    try {
      long now = Calendar.getInstance().getTimeInMillis();
      //set timestamp check
      if (!file.exists() || (file.exists() &&
          current.lastModified() > file.lastModified()) ||
          cacheTimeout < now - file.lastModified()) {
        String name = file.getAbsolutePath();
        name = name.substring(0,name.lastIndexOf("/")==-1?0:name.lastIndexOf("/"));
        new File(name).mkdirs();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        CacheResponseWrapper wrappedResponse =
          new CacheResponseWrapper(response, baos);
        chain.doFilter(req, wrappedResponse);

        FileOutputStream fos = new FileOutputStream(file);
        fos.write(baos.toByteArray());
        fos.flush();
        fos.close();
      }
    } catch (ServletException e) {
      if (!file.exists()) {
        throw new ServletException(e);
      }
    }
    catch (IOException e) {
      if (!file.exists()) {
        throw e;
      }
    }

    FileInputStream fis = new FileInputStream(file);
    String mt = sc.getMimeType(request.getRequestURI());
    response.setContentType(mt);
    ServletOutputStream sos = res.getOutputStream();
    for (int i = fis.read(); i!= -1; i = fis.read()) {
      sos.write((byte)i);
    }
  }

  public void init(FilterConfig filterConfig) {
    this.fc = filterConfig;
    String ct = fc.getInitParameter("cacheTimeout");
    if (ct != null) {
      cacheTimeout = 60*1000*Long.parseLong(ct);
    }
    this.sc = filterConfig.getServletContext();
  }

  public void destroy() {
    this.sc = null;
    this.fc = null;
  }
}