com.edgenius.wiki.webapp.servlet.StatusServlet.java Source code

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Here is the source code for com.edgenius.wiki.webapp.servlet.StatusServlet.java

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/* 
 * =============================================================
 * Copyright (C) 2007-2011 Edgenius (http://www.edgenius.com)
 * =============================================================
 * License Information: http://www.edgenius.com/licensing/edgenius/2.0/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2.0
 * as published by the Free Software Foundation.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * http://www.gnu.org/licenses/gpl.txt
 *  
 * ****************************************************************
 */
package com.edgenius.wiki.webapp.servlet;

import java.io.IOException;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import javax.jms.Queue;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.edgenius.core.Version;
import com.edgenius.core.webapp.BaseServlet;
import com.edgenius.wiki.service.NotifyMQObject;
import com.edgenius.wiki.service.SpaceService;

/**
 * System status check servlet - most for hosting service to check if this webapp is running.
 * @author Dapeng.Ni
 */
public class StatusServlet extends BaseServlet {
    private static final long serialVersionUID = 6556291757098976964L;
    private transient final Logger log = LoggerFactory.getLogger(StatusServlet.class);

    private Queue notifyQueue;
    private JmsTemplate jmsTemplate;

    private Lock jmsAckLocker = new ReentrantLock();
    private Condition jmsAckCondition = jmsAckLocker.newCondition();
    private String uuid;

    @Override
    protected void doService(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String jmsAckUuid = request.getParameter("uuid");
        if (StringUtils.isNotEmpty(jmsAckUuid)) {
            //This is JMS confirm request - Please note, for simply reason, here does not check if the UUID is that was sent one. 
            jmsAckLocker.lock();
            try {
                jmsAckCondition.signalAll();
            } finally {
                jmsAckLocker.unlock();
            }
            response.getWriter().write("Received");
        } else {
            String running = null;
            try {
                if (getSpaceService() == null) {
                    running = "Get system service bean failed";
                }
                if (getSpaceService().getSystemSpace() == null) {
                    running = "Get system sapce failed";
                }
                if (uuid == null) {
                    jmsTemplate = getJmsTemplate();
                    notifyQueue = getJmsQueue();

                    //wait JMS call back this servlet
                    jmsAckLocker.lock();
                    try {
                        uuid = UUID.randomUUID().toString();
                        NotifyMQObject message = new NotifyMQObject(NotifyMQObject.TYPE_SYSTEM_STATUS_CHECK, uuid);
                        jmsTemplate.convertAndSend(notifyQueue, message);

                        boolean ack = jmsAckCondition.await(10, TimeUnit.SECONDS);
                        if (!ack) {
                            running = "JMS is not response in 10 seconds!";
                        }
                    } finally {
                        uuid = null;
                        jmsAckLocker.unlock();
                    }
                } else {
                    log.warn("Last status check thread is not completed yet, this request is ignored");
                    running = "Last status check thread is not completed yet, this request is ignored";
                }
            } catch (Exception e) {
                uuid = null;
                log.error("System checking failed", e);
                running = "Exception on " + e.getMessage();
            }

            if (running == null)
                response.getWriter().write(
                        "<!--OK--><!--V1:" + Version.VERSION + "--><span style='color:#05BF54'>Running</span>");
            else {
                log.warn("System status check failed: {}", running);
                response.getWriter().write("<!--FAILED--><!--V1:" + Version.VERSION
                        + "--><span style='color:#CC3300'>" + running + "</span>");
            }
        }
    }

    private Queue getJmsQueue() {
        ApplicationContext ctx = WebApplicationContextUtils
                .getRequiredWebApplicationContext(this.getServletContext());
        return (Queue) ctx.getBean("notifyDestination");
    }

    private JmsTemplate getJmsTemplate() {
        ApplicationContext ctx = WebApplicationContextUtils
                .getRequiredWebApplicationContext(this.getServletContext());
        return (JmsTemplate) ctx.getBean("jmsTemplate");
    }

    private SpaceService getSpaceService() {

        ApplicationContext ctx = WebApplicationContextUtils
                .getRequiredWebApplicationContext(this.getServletContext());
        return (SpaceService) ctx.getBean(SpaceService.SERVICE_NAME);
    }

}