Question

我对Tomcat上下文侦听器有疑问。我想做什么：当tomcat启动时启动一个线程将基本上执行一些后台数据库操作。我已经实现了一个ContextLstener类，在web.xml中设置它并实现了一个简单的Thread-Class。

我的问题是，Tomcat启动此线程两次，有时甚至是3次，我不明白为什么。是的，我是Tomcat和Servlets的新手，是的，我有搜索stackoverflow的解决方案，但无法找到任何东西。

继承我的代码：的ServletContextListener：

public class EventToUserServletContextListener implements ServletContextListener {

    private DatabaseContextThread thread = null;

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        if ((thread == null) || (!thread.isAlive())) {
            System.out.println("STARTING CONTEXT THREAD");
            this.thread = new DatabaseContextThread();
            this.thread.start();
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
        try {
            System.out.println("STOPING CONTEXT THREAD");
            thread.doShutdown();
            thread.interrupt();
        } catch (Exception ex) {
            System.out.println("Error Stoping Thread: " + ex.getMessage());
        }
    }

}

线程类

public class DatabaseContextThread extends Thread {

    @Override
    public void run() {
        while (true) {
            try {
                //TODO Implement Context
                DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
                Date date = new Date();

                System.out.println(date + " THIS IS THREAD!!! " + this.toString());
                sleep(20000);
            } catch (InterruptedException ex) {
                Logger.getLogger(DatabaseContextThread.class.getName()).log(Level.SEVERE, null, ex);
            }

        }
    }

    public void doShutdown() {

    }
}

的web.xml

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
     version="3.1">
    <servlet>
        <servlet-name>Jersey RESTfull Server Thesis</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>jersey.config.server.provider.packages</param-name>
            <param-value>de.mk</param-value>
        </init-param>
        <load-on-startup>10</load-on-startup>
    </servlet>
    <listener>
        <listener-class>de.mk.dao.listener.EventToUserServletContextListener</listener-class>
    </listener>
    <servlet-mapping>
        <servlet-name>Jersey RESTfull Server Thesis</servlet-name>
        <url-pattern>/webapi/*</url-pattern>
    </servlet-mapping>
</web-app>

Sat Apr 12 11:26:27 CEST 2014这是线索！螺纹[线程6,5，主]

Sat Apr 12 11:26:29 CEST 2014这是线索！螺纹[线程8,5，主]

星期六4月12日11:26:47 CEST 2014这是线索！螺纹[线程6,5，主]

Sat Apr 12 11:26:49 CEST 2014这是线索！螺纹[线程8,5，主]

Answer 1

检查您定义上下文的次数。将为每个上下文执行上下文侦听器。如果使用虚拟主机，或者在war（META-INF / context.xml）中定义一个上下文，而在server.xml中定义其他上下文，则可以有多个上下文（不应在此处定义）。

Tomcat后台线程开始两次？

1 个答案: