addrefreshheaderfilter.java

来自「opennms得相关源码 请大家看看」· Java 代码 · 共 93 行

//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// For more information contact:
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//

package org.opennms.web;

import java.io.IOException;

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.HttpServletResponse;

/**
 * A filter that adds an HTTP <em>Refresh</em> header to a servlet or JSP's
 * response. The amount of time to wait before refresh is configurable.
 * 
 * @author <A HREF="mailto:[e-mail]">Lawrence Karnowski </A>
 * @author <A HREF="http://www.opennms.org/">OpenNMS </A>
 */
public class AddRefreshHeaderFilter extends Object implements Filter {
    protected FilterConfig filterConfig;

    protected String seconds = "108000"; // default is 30 mins

    /**
     * Adds a <em>Refresh</em> HTTP header before processing the request.
     * 
     * <p>
     * This is a strange implementation, because intuitively, you would add the
     * header after the content has been produced (in other words, after you had
     * already called {@link FilterChain#doFilter FilterChain.doFilter}.
     * However, the Servlet 2.3 spec (proposed final draft) states (albeitly in
     * an off-handed fashion) that you can only "examine" the response headers
     * after the <code>doFilter</code> call. Evidently this means that you
     * cannot change the headers after the <code>doFilter</code>. If you call
     * <code>setHeader</code> nothing happens.
     * </p>
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        ((HttpServletResponse) response).setHeader("Refresh", this.seconds);
        chain.doFilter(request, response);
    }

    public void init(FilterConfig config) {
        this.filterConfig = config;

        // read the seconds value from the config or use the default if not
        // found
        String seconds = this.filterConfig.getInitParameter("seconds");
        if (seconds != null)
            ;
        {
            this.seconds = seconds;
        }
    }

    public void destroy() {
    }

}