Question

I have developed the following program/architecture:

A) A Java servlet receives POST requests, gets the Parameters from the POST requests and stores them in a public static LinkedList:

public static LinkedList incomingQueue = new LinkedList<myObjects>();

That is, for every POST request I do this:

incomingQueue.push(myObject);

Now, I want to periodically access the Queue and perform processing on the Objects:

while(true){
doProcessing(incomingQueue);
wait(someTime);
}

Obviously, I don’t have a main class to do this. How do I create such a class that has access to the incomingQueue without being triggered by the servlet? What is the correct architecture to do this?

Thank you for your time.

Answer 1

First of all the queue should be placed in servlet context attributes (see: ServletContext.setAttribute(). Also access to this queue must be synchronized, consider ArrayBlockingQueue.

In plain servlets you can use ServletContextListener by starting a thread in contextInitialized() and interrupting it in contextDestroyed.

If you are using spring you can use @Scheduled annotation, in ejb: TimerService or @Schedule.

Finally there is a Timer class in standard Java. Last but not least, have a look at jms, it might be a better choice in your situation.