Java EJB @Schedule注释方法被调用两次

Question

我正在开发一个J2EE项目，简而言之，它在指定的时间自动向用户发送电子邮件，并允许用户从通过电子邮件发送给他们的网页下载文件。它工作得很好。

但是，使用@Schedule注释的计时器方法被调用了两次。该方法总是在运行时立即执行(我不希望这样)，然后在指定的时间稍后执行。我已经包含了部署应用程序时加载的Servlet代码、Schedule类和web.xml文件。

DeployApplicationServlet等级:

package downloadsupport;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import scheduleTimer.ScheduleEmail;
/**
 * Servlet implementation class InitializeApplicationServlet
 */
@WebServlet("/DeployApplicationServlet")
public class DeployApplicationServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DeployApplicationServlet() {
        super();
    }
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        PrintWriter out = response.getWriter();
        out.println("Web Application Started");
        ScheduleEmail se = new ScheduleEmail();
        se.sendAutomatedEmail();
    }
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
    }
}

ScheduleEmail class:

package scheduleTimer;
import java.util.Date;
import javax.ejb.Schedule;
import javax.ejb.Stateless;
import java.net.*;
import java.io.*;

@Stateless
public class ScheduleEmail {
    @Schedule(second = "0", minute = "10", hour = "12", dayOfWeek = "Wed")
    public void sendAutomatedEmail() {
        // Print Time to console for testing purposes
        System.out.println(new Date());
        // Invoke the SendEmailServlet at the designated time
        try {
            URL emailServlet = new
                URL("http://localhost:9081/downloadsupport/SendEmailServlet");
            URLConnection servletConn = emailServlet.openConnection();
            BufferedReader in = new BufferedReader(new InputStreamReader(
                        servletConn.getInputStream()));
            String inputLine;
            while ((inputLine = in.readLine()) != null)
                System.out.println(inputLine);
            in.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

web.xml config:

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    <display-name>downloadsupport</display-name>
    <servlet>
        <servlet-name>SendEmailServlet</servlet-name>
        <servlet-class>downloadsupport.SendEmailServlet</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>DeployApplicationServlet</servlet-name>
        <servlet-class>downloadsupport.DeployApplicationServlet</servlet-class>
    </servlet>
    <welcome-file-list>
        <welcome-file>DeployApplicationServlet</welcome-file>
        <!--  <welcome-file>SendEmailServlet</welcome-file> -->
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>DownloadServet</servlet-name>
        <servlet-class>downloadsupport.DownloadServlet</servlet-class>
    </servlet>
    <!--
 <servlet-mapping>
    <servlet-name>DownloadServlet</servlet-name>
    <url-pattern>/downloadServlet</url-pattern>
</servlet-mapping>
 -->
</web-app>

Answer 1

您的第一个不必要的呼叫是由您引起的，而不是由于服务器不工作。

不需要实例化ScheduleEmail。从servlet中删除这两行，它就可以正常工作了。

容器负责初始化bean并调用标记为@Schedule的方法

Answer 2

检查您的服务器实例。如果您在服务器上有2个节点。然后使它成为一个节点，ejb timer将按预期工作。