cachetag.java

ejb克斯人随风俗

/* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 
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 - Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
 
 - Redistribution 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.
 
 Neither the name of Sun Microsystems, Inc. or the names of
 contributors may be used to endorse or promote products derived
 from this software without specific prior written permission.
 
 This software is provided "AS IS," without a warranty of any
 kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES
 SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN
 OR ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR
 FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR
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 $Id: CacheTag.java,v 1.1 2004/04/15 03:43:52 yutayoshida Exp $ */

package com.sun.j2ee.blueprints.waf.view.taglibs.smart;

import java.io.IOException;
import java.util.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import javax.servlet.http.HttpServletRequest;

/**
 * A caching tag.
 */
public class CacheTag extends BodyTagSupport {

    private String scope;
    private String name;
    private long duration;
    private Entry entry;
    private String key;

    public void setScope(String s) { scope = s; }

    public void setName(String n) { name = n; }

    public void setDuration(long d) { duration = d; }

    public int doStartTag() throws JspTagException {
        HttpServletRequest req = 
            ((HttpServletRequest) pageContext.getRequest());

        key = req.getRequestURL().toString() 
            + '#' + name
            + '?' + req.getQueryString();

        if ("context".equals(scope)) {
            entry = (Entry) pageContext.getServletContext().getAttribute(key);
        } else if ("session".equals(scope)) {
            entry = (Entry) pageContext.getSession().getAttribute(key);
        }else if ("request".equals(scope)) {
            entry = (Entry) pageContext.getRequest().getAttribute(key);
        } else if ("page".equals(scope)) {
            entry = (Entry) pageContext.getAttribute(key);
        }
        if (entry != null && entry.isExpired()) {
            entry = null;
        }
        return (entry == null) ? EVAL_BODY_BUFFERED : SKIP_BODY;
    }

    public int doEndTag() throws JspTagException {
        if (entry == null) {
            BodyContent bc = getBodyContent();
            if (bc != null) {
                String content = bc.getString();
                entry = new Entry(content, duration);
                
                if ("context".equals(scope)) {
                    pageContext.getServletContext().setAttribute(key, entry);
                }
                else if ("session".equals(scope)) {
                    pageContext.getSession().setAttribute(key, entry);
                }
                else if ("request".equals(scope)) {
                    pageContext.getRequest().setAttribute(key, entry);
                }
                else if ("page".equals(scope)) {
                    pageContext.setAttribute(key, entry);
                }
                
                try {
                    JspWriter out = bc.getEnclosingWriter();
                    out.print(content);
                }
                catch (IOException ioe) {
                    System.err.println("Problems with writing...");
                }
            }
        } else {
            try {
                JspWriter out = pageContext.getOut();
                out.print(entry.getContent());
            }
            catch (IOException ioe) {
                System.err.println("Problems with writing...");
            }
        }
        //reset everything
        scope = null;
        name = null;
        duration = 0;
        entry = null;
        key = null;
        return EVAL_PAGE;
    }

    /*
     * An entry in the cache.
     */
    class Entry {

        private String content;
        private long timestamp;
        private long duration;

        public Entry(String content, long duration) {
            this.content = content;
            timestamp = System.currentTimeMillis();
            this.duration = duration;
        }

        public String getContent() { return content; }

        public boolean isExpired() {
            long currentTime = System.currentTimeMillis();
            return ((currentTime - timestamp) > duration);
        }
    }
}