how to start a function automatically on the system startup in java deployed on Apache Tomcat

Question

I have a java web application deployed on Apache tomcat.In my application there is a function that is continuously reading the data from database.As per my need this should never be stopped.Now my concern is suppose that the system restarts ..In this case i want my that function to be called automatically without any intervention from anywhere..but i have o idea how to achieve it..

I have googled about ServletContextListener but i am not getting how to use it in my case..

Any suggestion to solve the above issue will be heartedly welcomed.. Thanks in advance..

Answer 1

Write an implementation of ServletContextListener (org.myapp.Startup.java):

public class Startup implements ServletContextListener
{
    @Override
    public void contextDestroyed(ServletContextEvent sce) {}

    @Override
    public void contextInitialized(ServletContextEvent sce)
    {
        // Do your startup work here
    }

}

And add it to your web.xml:

<listener>
    <listener-class>org.myapp.Startup</listener-class>
</listener>