Question

I have oracle database 11.2, and I am trying to get oracle change notification working. But it does not seem to notify me, I am using ojdbc6.jar. Table is getting registered into notification; which is verified by running

select * from USER_CHANGE_NOTIFICATION_REGS

When I execute an update on table from external client, my listener is not getting called. But when I shutdown/start database it does notify.

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
import oracle.jdbc.OracleConnection;
import oracle.jdbc.OracleDriver;
import oracle.jdbc.OracleStatement;
import oracle.jdbc.dcn.DatabaseChangeEvent;
import oracle.jdbc.dcn.DatabaseChangeListener;
import oracle.jdbc.dcn.DatabaseChangeRegistration;

public class DBChangeNotification
{
  static final String USERNAME= "scott";
  static final String PASSWORD= "tiger";
  static String URL;

  public static void main(String[] argv)
  {
    if(argv.length < 1)
    {
      System.out.println("Error: You need to provide the URL in the first argument.");
      System.out.println("  For example: > java -classpath .:ojdbc5.jar DBChangeNotification \"jdbc:oracle:thin: @(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=yourhost.yourdomain.com)(PORT=1521)) CONNECT_DATA=(SERVICE_NAME=yourservicename)))\"");

      System.exit(1);
    }
    URL = argv[0];
    DBChangeNotification demo = new DBChangeNotification();
    try
    {
      demo.run();
    }
    catch(SQLException mainSQLException )
    {
      mainSQLException.printStackTrace();
    }
  }

  void run() throws SQLException
  {
    OracleConnection conn = connect();

    // first step: create a registration on the server:
    Properties prop = new Properties();

    // if connected through the VPN, you need to provide the TCP address of the client.
    // For example:
    // prop.setProperty(OracleConnection.NTF_LOCAL_HOST,"14.14.13.12");

    // Ask the server to send the ROWIDs as part of the DCN events (small performance
    // cost):
    prop.setProperty(OracleConnection.DCN_NOTIFY_ROWIDS,"true");
    // 
    //Set the DCN_QUERY_CHANGE_NOTIFICATION option for query registration with finer granularity.
    prop.setProperty(OracleConnection.DCN_QUERY_CHANGE_NOTIFICATION,"true");

    // The following operation does a roundtrip to the database to create a new
    // registration for DCN. It sends the client address (ip address and port) that
    // the server will use to connect to the client and send the notification
    // when necessary. Note that for now the registration is empty (we haven't registered
    // any table). This also opens a new thread in the drivers. This thread will be
    // dedicated to DCN (accept connection to the server and dispatch the events to 
    // the listeners).
    DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotification(prop);

    try
    {
      // add the listenerr:
      DCNDemoListener list = new DCNDemoListener(this);
      dcr.addListener(list);

      // second step: add objects in the registration:
      Statement stmt = conn.createStatement();
      // associate the statement with the registration:
      ((OracleStatement)stmt).setDatabaseChangeRegistration(dcr);
      ResultSet rs = stmt.executeQuery("select rowid from dept where 1 = 2");
      while (rs.next())
      {}
      String[] tableNames = dcr.getTables();
      for(int i=0;i<tableNames.length;i++)
        System.out.println(tableNames[i]+" is part of the registration.");
      rs.close();
      stmt.close();
    }
    catch(SQLException ex)
    {
      // if an exception occurs, we need to close the registration in order
      // to interrupt the thread otherwise it will be hanging around.
      if(conn != null)
        conn.unregisterDatabaseChangeNotification(dcr);
      throw ex;
    }
    finally
    {
      try
      {
        // Note that we close the connection!
        conn.close();
      }
      catch(Exception innerex){ innerex.printStackTrace(); }
    }

    synchronized( this ) 
    {

      // wait until we get the event
      try{ this.wait();} catch( InterruptedException ie ) {}
    }

    // At the end: close the registration (comment out these 3 lines in order
    // to leave the registration open).
    OracleConnection conn3 = connect();
    conn3.unregisterDatabaseChangeNotification(dcr);
    conn3.close();
  }

  /**
   * Creates a connection the database.
   */
  OracleConnection connect() throws SQLException
  {
    OracleDriver dr = new OracleDriver();
    Properties prop = new Properties();
    prop.setProperty("user",DBChangeNotification.USERNAME);
    prop.setProperty("password",DBChangeNotification.PASSWORD);
    return (OracleConnection)dr.connect(DBChangeNotification.URL,prop);
  }
}
/**
 * DCN listener: it prints out the event details in stdout.
 */
class DCNDemoListener implements DatabaseChangeListener
{
  DBChangeNotification demo;
  DCNDemoListener(DBChangeNotification dem)
  {
    demo = dem;
  }
  public void onDatabaseChangeNotification(DatabaseChangeEvent e)
  {
    Thread t = Thread.currentThread();
    System.out.println("DCNDemoListener: got an event ("+this+" running on thread "+t+")");
    System.out.println(e.toString());
    synchronized( demo ){ demo.notify();}
  }
}

Answer 1

Well, this change notification simply doesn’t work. I am going with another route Oracle Advance Queue JMS messaging instead

oracle.jms.AQjmsSession
oracle.jms.AQjmsFactory