Tomcat启动完成后再执行一个指定的方法 - 不影响Tomcat的启动时间

本文主要介绍Tomcat启动真正完成后（即在eclipse的控制台上出现类似于Server started in 2300ms这样的消息后）执行一个操作。

如下的3种方法都是在Tomcat启动过程中执行的，这样会影响Tomcat的启动时间，从而造成Tomcat不能启动成功：
1.配置一个Servlet默认自动启动。
2.配置一个Listener来启动
3.实现Spring的InitializingBean接口

要想不影响Tomcat的启动，便联想到了异步调用。即无非就是新创建了一个线程来单独执行，这样Tomcat执行到相应的操作就可以直接继续下去了，不会处于等待的状态，避免了启动超时。基于这样的思想，可以有两种方法来完成：

方法一：使用如上三种方式中的任何一种来在启动Tomcat的过程中执行相应的方法，然后在执行的过程中使用另一个线程来执行：比如说将要执行的方法所在的类继承HttpServlet并在web.xml中配置，然后在该Servlet的init中去调用想要执行的方法时（假设这个方法名叫start())，启动另一个线程来执行，具体代码如下。

Java代码

/**
*
*/
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方法会在Tomcat启动的时候执行
@Override
public void init() throws ServletException {
FutureTask<String> task = new FutureTask<String>(new Callable<String>(){
@Override
public String call() throws Exception {
start(); // 使用另一个线程来执行该方法，会避免占用Tomcat的启动时间
return "Collection Completed";
}
});
new Thread(task).start();
}
// 希望Tomcat启动结束后执行的方法
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方法会在Tomcat启动的时候执行
	@Override
	public void init() throws ServletException {
		FutureTask<String> task = new FutureTask<String>(new Callable<String>(){

	       @Override
	       public String call() throws Exception {
		start(); // 使用另一个线程来执行该方法，会避免占用Tomcat的启动时间
		return "Collection Completed";
	       }
			
		});
		
		new Thread(task).start();
	}

        // 希望Tomcat启动结束后执行的方法
	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代码

<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启动后再执行该方法,Spring中的Timer非常简单，这个地方不想讲解了，Quartz相对更复杂些，下面主要介绍下在Spring中怎么样使用Quartz来实现上面的需求：

实现Job接口的任务实现类：

Java代码  

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务

Xml代码  

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

<!--定时器任务配置（开始）-->       

    <!--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>  

    <!--定时器任务配置（结束）-->