Demonstration of Container managed concurrency in Singleton Beans (default, locking type not explicitly specified )

MySingletonBean.java

package com.abhirockzz.wordpress.ejb.lifecycle.singleton;
 
import com.abhirockzz.wordpress.ejb.lifecycle.stateful.MyStatefulBean;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ejb.Singleton;
import javax.ejb.Startup;
 
@Singleton
@Startup
public class MySingletonBean {
 
    public void act() {
        System.out.println("Entered MySingletonBean/act() on " + new Date().toString() + " . Singleton instance " + this.hashCode() + " Thread : " + Thread.currentThread().getName());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException ex) {
            Logger.getLogger(MyStatefulBean.class.getName()).log(Level.SEVERE, null, ex);
        }
 
        System.out.println("Exit MySingletonBean/act() on " + new Date().toString() + " . Singleton instance " + this.hashCode() + " Thread : " + Thread.currentThread().getName());
 
    }
}

SingletonTestServlet.java

package com.abhirockzz.wordpress.ejb.lifecycle.singleton;
 
import java.io.IOException;
import java.util.Date;
import javax.inject.Inject;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@WebServlet(name = "SingletonTestServlet", urlPatterns = {"/SingletonTestServlet"})
public class SingletonTestServlet extends HttpServlet {
 
    public SingletonTestServlet() {
    }
 
    @Inject
    MySingletonBean mySingleton;
 
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("Entered SingletonTestServlet/doGet() on " + new Date().toString() + " . Servlet instance " + this.hashCode() + " Thread : " + Thread.currentThread().getName());
        mySingleton.act();
    }
 
}