listaction.java

高效海量访问系统

/*
 * Created on 2005-1-18
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package com.struts.action;

import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.PageContext;

import org.apache.log4j.Logger;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.actions.DispatchAction;

import com.opensymphony.oscache.base.Cache;
import com.opensymphony.oscache.base.NeedsRefreshException;
import com.opensymphony.oscache.web.ServletCacheAdministrator;


/**
 * @author jmwang
 * 
 * TODO To change the template for this generated type comment go to Window -
 * Preferences - Java - Code Style - Code Templates
 */
public class ListAction extends DispatchAction {
	//	实例话一个log4j实例
	static Logger log = Logger.getLogger(ListAction.class);	
	ServletCacheAdministrator admin = null;
	Cache oscache = null;

	/**
	 * 
	 * @param mapping
	 * @param form
	 * @param req
	 * @param res
	 * @return
	 */
	public ActionForward test(ActionMapping mapping, ActionForm form,
			HttpServletRequest req, HttpServletResponse res) {
	    String testOsEntryKey=null;
	    String oscachekey="testkey";
		String oscachegroup="testgroup";
		String  cachecontent="";
		try {			
			if (admin == null) {
				admin = ServletCacheAdministrator.getInstance(this.getServlet()
						.getServletContext());

			}
			if (oscache == null) {
				oscache = admin.getCache(req, PageContext.APPLICATION_SCOPE);
			}
			//得到对应得oscache得entrykey			
			testOsEntryKey = admin.generateEntryKey(oscachekey, req,PageContext.APPLICATION_SCOPE);
			log.debug("testOsEntryKey:"+testOsEntryKey);
			//定义刷新周期为10秒
			int RefreshPeriod=10; 
			//如果oscache过期，将抛出异常，那么再异常部分取得新得内容更新到oscache中
			Object osobj = oscache.getFromCache(testOsEntryKey,RefreshPeriod);		
		} catch (NeedsRefreshException nrfe) {
			log.debug("Cache已经过期！");
			String oldCache = (String) nrfe.getCacheContent();			
			try {
				//生成新数据
			   Date date=new Date();
			   cachecontent=date.toGMTString();
				//避免死锁因为NeedsRefreshException产生时,如果不条用update或者put得相关操作,oscache将锁该cache				
				oscache.putInCache(testOsEntryKey, oldCache,
						new String[] { oscachegroup });
				//刷新group
				oscache.flushEntry(testOsEntryKey);
			} catch (Exception e1) {
				log.error("刷新OsCache时异常,使用oldCache..." + e1.toString());
				e1.printStackTrace();
				oscache.putInCache(testOsEntryKey, nrfe
								.getCacheContent(),
								new String[] { oscachegroup });

			}

		}
		req.setAttribute("cacheContent", cachecontent);
		return mapping.findForward("success");
	}

	
}