java - jdbc: oracle database change notification & duplicate events

Question

I need some Listener for any change(update, insert, delete) of Oracle database table.

Problem: I get many detection by single update on my table.

I think its oracle cache etc.

Is it possible only real changes to detect?

my code:

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 OracleDCN {
    static final String USERNAME = "scott";
    static final String PASSWORD = "tiger";
    static String URL = "jdbc:oracle:thin:@localhost:1521:stingdev";

    public static void main(String[] args) {
        OracleDCN oracleDCN = new OracleDCN();
        try {
            oracleDCN.run();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private void run() throws Exception{
        OracleConnection conn = connect();
        Properties prop = new Properties();
        prop.setProperty(OracleConnection.DCN_NOTIFY_ROWIDS, "true");
        DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotification(prop);

        try{
            dcr.addListener(new DatabaseChangeListener() {

                public void onDatabaseChangeNotification(DatabaseChangeEvent dce) {
                    System.out.println("Changed row id : "+dce.getTableChangeDescription()[0].getRowChangeDescription()[0].getRowid().stringValue());
                }
            });

            Statement stmt = conn.createStatement();
            ((OracleStatement) stmt).setDatabaseChangeRegistration(dcr);
            ResultSet rs = stmt.executeQuery("select * from EXAMPLE where ID=1");
            while (rs.next()) {
            }
            rs.close();
            stmt.close();
        }catch(SQLException ex){
            if (conn != null)
            {
                conn.unregisterDatabaseChangeNotification(dcr);
                conn.close();
            }
            throw ex;
        }
    }

    OracleConnection connect() throws SQLException {
        OracleDriver dr = new OracleDriver();
        Properties prop = new Properties();
        prop.setProperty("user", OracleDCN.USERNAME);
        prop.setProperty("password", OracleDCN.PASSWORD);
        return (OracleConnection) dr.connect(OracleDCN.URL, prop);
    }
}

Output:

Changed row id : AAAFSzAAAAAAAG8AAA
Changed row id : AAAFSzAAAAAAAG8AAA
Changed row id : AAAFSzAAAAAAAG8AAA
Changed row id : AAAFSzAAAAAAAG8AAA

Answer 1

Problem was I registered to database many times. The solution was check registered user for change events before register.

I checked that with this query:

select TABLE_NAME 
from USER_CHANGE_NOTIFICATION_REGS