Question

I have a problem where my class is performing the first run method after which it is not proceeding into a second, overidden run method.

The program execution beings in a controller class which has a main method and a thread pool:

public class RunnableController {
    // Main method
    public static void main(String[] args) throws InterruptedException {
        try {
            RunnableController controller = new RunnableController();
            controller.initializeDb();
            controller.initialiseThreads();
            System.out.println("Polling");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void initialiseThreads() {      
        try {
            threadExecutorRead = Executors.newFixedThreadPool(10);
            PollingSynchronizer read = new PollingSynchronizer(incomingQueue, dbConncetion);
            threadExecutorRead.submit(read);
        } catch (Exception e){
            e.printStackTrace();
        }   
    }
}

My poller class which fetches new data and should do updating simulateously:

public class PollingSynchronizer implements Runnable {
   public PollingSynchronizer(Collection<KamMessage> incomingQueue,
         Connection dbConnection) {
      super();
      this.incomingQueue = incomingQueue;
      this.dbConnection = dbConnection;
   }

   private int seqId;

   public int getSeqId() {
      return seqId;
   }

   public void setSeqId(int seqId) {
      this.seqId = seqId;
   }

   // The method which runs Polling action and record the time at which it is done
   public void run() {
      int seqId = 0;

      while (true) {
         List<KamMessage> list = null;

         try {
            list = fullPoll(seqId);

            if (!list.isEmpty()) {
               seqId = list.get(0).getSequence();
               incomingQueue.addAll(list);
               this.outgoingQueue = incomingQueue;
               System.out.println("waiting 3 seconds");
               System.out.println("new incoming message");
               Thread.sleep(3000);//at this wait I should execute run()

               //when I debug my execution stops here and throws " Class not found Exception "
               // its does not enters the message processor class 
               MessageProcessor processor = new MessageProcessor() {
                  //the run method which should fetch the message processor class.
                  final public void run() {
                     MessageProcessor(outgoingQueue).generate(outgoingQueue);
                  }
               };
              new Thread(processor).start();
            }
         } catch (Exception e1) {
            e1.printStackTrace();
         }
      }
   }
}

My message processor class:

public abstract class MessageProcessor implements Runnable {
   private Connection dbConnection;
   Statement st = null;
   ResultSet rs = null;
   PreparedStatement pstmt = null;
   private Collection<KamMessage> outgoingQueue;

   public KamMsg804 MessageProcessor(Collection<KamMessage> outgoingQueue,
         Connection dbConnection) {
      this.outgoingQueue = outgoingQueue;
      this.dbConnection = dbConnection;
      return (KpiMsg804) fetchedMessages;
   }

   public Collection<KamMessage> generate(Collection<KamMessage> outgoingQueue) {
      while (true) {
         try {
            while (rs.next()) {
               KamMessage filedClass = convertRecordsetToPojo(rs);
               outgoingQueue.add(filedClass);
            }

            for (KamMessage pojoClass : outgoingQueue) {
               KamMsg804 updatedValue = createKamMsg804(pojoClass);
               System.out.print(" " + pojoClass.getSequence());
               System.out.print(" " + pojoClass.getTableName());
               System.out.print(" " + pojoClass.getAction());
               System.out.print(" " + updatedValue.getKeyInfo1());
               System.out.print(" " + updatedValue.getKeyInfo2());
               System.out.println(" " + pojoClass.getEntryTime());
            }
            return outgoingQueue;
         } catch (SQLException e) {
            e.printStackTrace();
         }
      }
   }
}

My problem is exactly at the second run(9 method where I am getting exception in MessageProcessor class and it loops back to Polling.

1. How do I implement multithreading here, as when the thread sleeps for 3 seocnds in polling it should simultaneously update the database.
2. After which, how can the data be fed and updated back into the db.

My program flow – I have three classes:
1.Controller
2.PollerSynchro
3.Msgprocessor

I have database records, which are converted into POJO form and stored in a Collection. With these POJOs my classes try to do multiprocessing and updating in a single stretch.

1. Controller – has the thread pool, initiates poller class with poll method – done

2. Poller – should poll for new incoming messages and stores it in incoming queue – done

3. MsgProcessor – should look for new incoming messages and pass them from outgoing queue to incoming queue – also done

Problem:

Now my problem is

1. I have to implement this update while the poll thread sleeps for 3 sec,

2. In my code for the second void run() method in the Poller class, the outgoing queue is not passed and fed to the messageprocessor class for updating. My flow of execution only just loops back to first run method and am getting Class exception.

Please help me to solve these problems.

Answer 1

I can’t sugar coat this, your code is a mess. However, as far as why your message processor code is not being executed, you never actually start the thread you created with this code:

MessageProcessor processor = new MessageProcessor() {
    // the run method which should fetch the message processor class.
    final public void run() {
         MessageProcessor(outgoingQueue).generate(outgoingQueue);                    
    }
};

Ignoring the confusingly named method being called, your code should look more like this:

Message processor = new MessageProcessor() {
    // the run method which should fetch the message processor class.
    final public void run() {
         MessageProcessor(outgoingQueue).generate(outgoingQueue);                    
    }
};

new Thread(processor).start();