Tomcat啓動完成後再執行一個指定的方法 - 不影響Tomcat的啓動時間

本文主要介紹Tomcat啓動真正完成後（即在eclipse的控制檯上出現類似於Server started in 2300ms這樣的消息後）執行一個操作。

如下的3種方法都是在Tomcat啓動過程中執行的，這樣會影響Tomcat的啓動時間，從而造成Tomcat不能啓動成功：
1.配置一個Servlet默認自動啓動。
2.配置一個Listener來啓動
3.實現Spring的InitializingBean接口

要想不影響Tomcat的啓動，便聯想到了異步調用。即無非就是新創建了一個線程來單獨執行，這樣Tomcat執行到相應的操作就可以直接繼續下去了，不會處於等待的狀態，避免了啓動超時。基於這樣的思想，可以有兩種方法來完成：

方法一：使用如上三種方式中的任何一種來在啓動Tomcat的過程中執行相應的方法，然後在執行的過程中使用另一個線程來執行：比如說將要執行的方法所在的類繼承HttpServlet並在web.xml中配置，然後在該Servlet的init中去調用想要執行的方法時（假設這個方法名叫start())，啓動另一個線程來執行，具體代碼如下。

Java代碼

/**
*
*/
package com.ebay.montage.pm;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
import com.ebay.montage.pm.collector.NucleonEventDataCollector;
import com.ebay.montage.pm.constants.CMConstants;
import com.ebay.montage.pm.utils.ConfigurationUtils;
import com.ebay.montage.pm.utils.LoggerUtils;
import com.ebay.system.ShutdownAwaitLatch;
/**
* Trigger to consume data from Nucleon Event Bus
*
* @author Josh Wang(Sheng)
*
* @email [email protected]
*/
@Component("processor")
public class NucleonEventProcessor extends HttpServlet {
private static final long serialVersionUID = -9045451275234606838L;
private static final Logger log = Logger.getLogger(NucleonEventProcessor.class);
// Servlet的init方法會在Tomcat啓動的時候執行
@Override
public void init() throws ServletException {
FutureTask<String> task = new FutureTask<String>(new Callable<String>(){
@Override
public String call() throws Exception {
start(); // 使用另一個線程來執行該方法，會避免佔用Tomcat的啓動時間
return "Collection Completed";
}
});
new Thread(task).start();
}
// 希望Tomcat啓動結束後執行的方法
private void start() {
if (ConfigurationUtils.isEnableEventCollector()) {
String topic = CMConstants.NUCLEON_EVENT_TOPIC;
new NucleonEventDataCollector().collect(topic);
LoggerUtils.info(log, "NuclenonEventDataCollector started to consume data from Collector Bus - NUCLEON_EVENT_TOPIC: " + topic);
new ShutdownAwaitLatch().awaitForShutdown();
LoggerUtils.info(log, "Complete processing and publishing Event Data");
} else {
log.info("There disable the collector, please enable it on dev/qa/prod property if needed");
}
}
}

/**
 * 
 */
package com.ebay.montage.pm;


import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

import com.ebay.montage.pm.collector.NucleonEventDataCollector;
import com.ebay.montage.pm.constants.CMConstants;
import com.ebay.montage.pm.utils.ConfigurationUtils;
import com.ebay.montage.pm.utils.LoggerUtils;
import com.ebay.system.ShutdownAwaitLatch;

/**
 * Trigger to consume data from Nucleon Event Bus
 * 
 * @author Josh Wang(Sheng)
 *
 * @email  [email protected]
 */
@Component("processor")
public class NucleonEventProcessor extends HttpServlet {
	
	private static final long serialVersionUID = -9045451275234606838L;

	private static final Logger log = Logger.getLogger(NucleonEventProcessor.class);
	
	// Servlet的init方法會在Tomcat啓動的時候執行
	@Override
	public void init() throws ServletException {
		FutureTask<String> task = new FutureTask<String>(new Callable<String>(){

	       @Override
	       public String call() throws Exception {
		start(); // 使用另一個線程來執行該方法，會避免佔用Tomcat的啓動時間
		return "Collection Completed";
	       }
			
		});
		
		new Thread(task).start();
	}

        // 希望Tomcat啓動結束後執行的方法
	private void start() {
		if (ConfigurationUtils.isEnableEventCollector()) {
			String topic = CMConstants.NUCLEON_EVENT_TOPIC;
			
			new NucleonEventDataCollector().collect(topic);
			
			LoggerUtils.info(log, "NuclenonEventDataCollector started to consume data from Collector Bus - NUCLEON_EVENT_TOPIC: " + topic);		
			new ShutdownAwaitLatch().awaitForShutdown();
			LoggerUtils.info(log, "Complete processing and publishing Event Data");

		} else {
			log.info("There disable the collector, please enable it on dev/qa/prod property if needed");
		}
		
	}


}

web.xml中的配置

Java代碼

<servlet>
<servlet-name>event-collector</servlet-name>
<servlet-class>com.ebay.montage.pm.NucleonEventProcessor</servlet-class>
<load-on-startup>5</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>event-collector</servlet-name>
<url-pattern>/event-collect</url-pattern>
</servlet-mapping>

    <servlet>
    	<servlet-name>event-collector</servlet-name>
    	<servlet-class>com.ebay.montage.pm.NucleonEventProcessor</servlet-class>
    	<load-on-startup>5</load-on-startup>
    </servlet>
    
    <servlet-mapping>
    	<servlet-name>event-collector</servlet-name>
    	<url-pattern>/event-collect</url-pattern>
    </servlet-mapping>

方法二：使用Spring的Timer或者是著名的Quartz在Tomcat啓動後再執行該方法,Spring中的Timer非常簡單，這個地方不想講解了，Quartz相對更復雜些，下面主要介紹下在Spring中怎麼樣使用Quartz來實現上面的需求：

實現Job接口的任務實現類：

Java代碼  

public class InitJob implements Job {
@Override
public void execute(JobExecutionContext arg0) throws JobExecutionException {
// TODO Auto-generated method stub
}
public void executeA() throws JobExecutionException {
// TODO Auto-generated method stub
.........
}

Spring配置文件中配置的任務

Xml代碼  

<bean id="initJob" class="com.xxx.services.InitJob" />  

<!--定時器任務配置（開始）-->       

    <!--配置JOB-->  

    <bean id="initJobDetail"  

        class="org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean">  

        <property name="targetObject" ref="initJob" />  

        <property name="targetMethod" value="executeA" />  

<!--         <property name="arguments" /> -->  

    </bean>  

    <!--配置Trigger-->  

    <bean id="initTrigger"    

        class="org.springframework.scheduling.quartz.SimpleTriggerBean">    

        <property name="jobDetail" ref="initJobDetail" />    

        <property name="startDelay" value="1000" />  

        <property name="repeatInterval" value="0" />  

        <property name="repeatCount" value="0" />  

    </bean>  

    <!--配置Scheduler-->  

    <bean id="schedulerFactory"    

        class="org.springframework.scheduling.quartz.SchedulerFactoryBean" autowire="no">    

        <property name="triggers">    

            <list>    

                <ref bean="initTrigger" />    

            </list>    

        </property>    

        <property name="autoStartup" value="true"/>  

    </bean>  

    <!--定時器任務配置（結束）-->