Question

I am trying to do multi-threading here, now I have to update my database using DbHandler class

The program execution begins 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 initialUpdate()
{
    DBhandler dbhandler = new DBhandler();
    dbhandler.updateDb(getOutgoingQueue());
}

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() {
               RunnableController.setOutgoingQueue(generate(outgoingQueue));
              }
           };
          new Thread(processor).start();
        }
     } catch (Exception e1) {
        e1.printStackTrace();
     }
  }
 }
}

My message processor class:

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

public Collection<KamMessage> MessageProcessor(Collection<KamMessage> outgoingQueue){
    this.outgoingQueue = outgoingQueue;
    this.dbConnection = dbConnection;
    return outgoingQueue;
}
/**
 * Method for updating new values into database in preference for dummy processing of message
 * @param outgoingQueue 
 * @return 
 */
@SuppressWarnings("javadoc")
public Collection<KamMessage> generate(Collection<KamMessage> outgoingQueue)
{
        for (KamMessage pojoClass : outgoingQueue) {
            KamMessage 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;
}

/**
 * 
 * @param pojoClass 
 * @return msg
 */
public KamMessage createKamMsg804(KamMessage pojoClass)
{
    if(pojoClass.getAction() == 804){
    pojoClass.setKeyInfo1("ENTITYKEY9");
    pojoClass.setKeyInfo2("STATUSKEY9");
    }
    return pojoClass;
}
private KamMessage convertRecordsetToPojo(ResultSet rs) throws SQLException {

    KamMessage msg = new KamMessage();
    int sequence = rs.getInt("SEQ");
    msg.setSequence(sequence);
    String tablename = rs.getString("TABLENAME");
    msg.setTableName(tablename);
    Timestamp entrytime = rs.getTimestamp("ENTRYTIME");
    Date entryTime = new Date(entrytime.getTime());
    msg.setEntryTime(entryTime);
    Timestamp processingtime=rs.getTimestamp("PROCESSINGTIME");
    if(processingtime!=null){
        Date processingTime = new Date(processingtime.getTime());
        msg.setProcessingTime(processingTime);   
    }
    String keyInfo1 = rs.getString("KEYINFO1");
    msg.setKeyInfo1(keyInfo1);
    String keyInfo2 = rs.getString("KEYINFO2");
    msg.setKeyInfo2(keyInfo2);
    return msg;
}


@Override
 public void run() {

    // TODO Auto-generated method stub

 }

  }

This is my DBhandler Class, which should do updating in database

         public class DBhandler {
  Connection conn = null;
Statement st = null;
ResultSet rs = null;
PreparedStatement pstmt = null;

public DBhandler(){
    super();
}

/**
 * Method to initialize the database connection
 * @return conn
 * @throws Exception 
 * 
 */
public Connection initializeDB() throws Exception {
    System.out.println("JDBC connection");
    DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
    conn = DriverManager.getConnection("jdbc:oracle:thin:@VM-SALES-
           MB:1521:SALESDB1","bdeuser", "edb"); // Connection for Database SALES-DB1   
    return conn;
}

 //The method for updating Database

  public void updateDb(Collection<KpiMessage> updatedQueue){
    for(KpiMessage pojoClass : updatedQueue){
       //**How the query should be used so that it gets last sequence vale and Updates into   
            Database**
           String query = "UPDATE msg_new_to_bde Set KEYINFO1= ?, KEYINFO2 = ? WHERE SEQ =  and 
           action = 804";   
      }
}
/**
 * Method for Closing the connection
 * @throws Exception 
 *
 */

     public void closeDB() throws Exception { 
    st.close();
    conn.close();
   }

    }

I just need to Update the database using update query in this class(DbHAndler) by calling the updatedQueue in the controller class.

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.

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

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

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

DbHandler- which should update in the database.

Problem:

Now my problem is

I have to implement this update while the poll thread sleeps for 3 sec -Done

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-Resolved

How to Update this in the database in Dbhanler class

Please help me to solve these problems.

Answer 1

The exception seems to come from this line (is this MessageProcessor.java line 38?)

return (KpiMsg804) fetchedMessages;

The fetchedMessages at this point seem to be an ArrayList.