CODEWITHSUNDEEP
javajakarta-ee
user1305398
user1305398

Reputation: 3690

Where to instantiate the class

I have one plain .java class. In that class I'm using a Timer class schedule method, to schedule a task.

The problem is I'm using a Java EE application, and I dont know where to intantiate this class; from a Servlet or any thing like that? I want to instantiate that class only once when my application goes up.

Upvotes: 3

Views: 429

Answers (3)

Hidalgo
Hidalgo

Reputation: 765

 public class YourServlet extends HttpServlet {
 private YourClass instance;

 public void init() throws ServletException {
      instance = new YourClass();
 }
 //code
 }

By instantiating your class in the init method, you will make sure that your class will be instantiated only once, because in Java EE applications, Servlets are loaded into the server memory only once.

Upvotes: 1

Carlos Gavidia-Calderon
Carlos Gavidia-Calderon

Reputation: 7253

In Quartz -a popular scheduler- is a common practice to configure Jobs in a the init method of a Servlet with the load-on-startup attribute set to true:

From this article, in web.xml you should do this:

<servlet>
    <servlet-name>QuartzInitializer</servlet-name>
    <display-name>Quartz Initializer Servlet</display-name>
    <servlet-class>org.quartz.ee.servlet.QuartzInitializerServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

And then conigure Jobs in your servlet:

public class QuartzServlet extends GenericServlet {
    public void init(ServletConfig config) throws ServletException {
    super.init(config);
    // And continue with your configuration

PS: I strongly recomend you to use Quartz

Upvotes: 0

Bozho
Bozho

Reputation: 597124

You probably need a ServletContextListener and its method contextInitialized(..). It is invoked once, when your application is initialized.

You map the listener with either @WebListener or with <listener><listener-class>..</...> in web.xml

Upvotes: 4

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