I am implementing DCN to get notifications for records being inserted into a table. When I try inserting records, either within the application or with external scripts, it does not show the events in the console.

The next code is my implementation:

package co.app.dcn;

import oracle.jdbc.OracleConnection;
import oracle.jdbc.OracleDriver;
import oracle.jdbc.OracleStatement;
import oracle.jdbc.dcn.DatabaseChangeRegistration;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

@Component
public class OracleDCNListener {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Value("${spring.datasource.username}")
    private String DCN_USER;

    @Value("${spring.datasource.password}")
    private String DCN_PASSWORD;

    @Value("${spring.datasource.url}")
    private String DCN_URL;

    @PostConstruct
    public void initialize() throws SQLException {


        var conn = connect();

        var prop = new Properties();

        prop.setProperty(OracleConnection.DCN_NOTIFY_ROWIDS, "true");
        prop.setProperty(OracleConnection.DCN_QUERY_CHANGE_NOTIFICATION, "true");

        DatabaseChangeRegistration dcr = conn.registerDatabaseChangeNotification(prop);

        try {
            DCNListener list = new DCNListener(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 * FROM CONTRATOS.CON_ESTADOS_PAGOS_CONTRATOS_NOTIFY");

            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 (conn != null)
                conn.unregisterDatabaseChangeNotification(dcr);
            throw ex;
        } finally {
            try {
                // Note that we close the connection!
                conn.close();
            } catch (Exception innerex) {
                innerex.printStackTrace();
            }
        }

        synchronized (this) {
            // The following code modifies the dept table and commits:
            try {
                OracleConnection conn2 = connect();
                conn2.setAutoCommit(false);
                Statement stmt2 = conn2.createStatement();
                stmt2.executeUpdate("insert into contratos.CON_ESTADOS_PAGOS_CONTRATOS_NOTIFY (ID, ID_CLASE_DOCUMENTO, NUMERO_DOCUMENTO, OBSERVACIONES, ID_ESTADO, DESCRIPCION_ESTADO, FECHA_HORA_CREACION) values (99999920, 0, 0, ' ', 0, ' ', ' ')",
                        Statement.RETURN_GENERATED_KEYS);
                ResultSet autoGeneratedKey = stmt2.getGeneratedKeys();
                if (autoGeneratedKey.next())
                    System.out.println("inserted one row with ROWID=" + autoGeneratedKey.getString(1));
                stmt2.executeUpdate("insert into contratos.CON_ESTADOS_PAGOS_CONTRATOS_NOTIFY (ID, ID_CLASE_DOCUMENTO, NUMERO_DOCUMENTO, OBSERVACIONES, ID_ESTADO, DESCRIPCION_ESTADO, FECHA_HORA_CREACION) values (99999922, 0, 0, ' ', 0, ' ', ' ')",
                        Statement.RETURN_GENERATED_KEYS);
                autoGeneratedKey = stmt2.getGeneratedKeys();
                if (autoGeneratedKey.next())
                    System.out.println("inserted one row with ROWID=" + autoGeneratedKey.getString(1));
                stmt2.close();
                conn2.commit();
                conn2.close();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }

            // 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();
    }

    OracleConnection connect() throws SQLException {
        OracleDriver dr = new OracleDriver();
        Properties prop = new Properties();
        prop.setProperty("user", DCN_USER);
        prop.setProperty("password", DCN_PASSWORD);

        return (OracleConnection) dr.connect(DCN_URL, prop);
    }

}

package co.app.dcn;

import oracle.jdbc.dcn.DatabaseChangeEvent;
import oracle.jdbc.dcn.DatabaseChangeListener;

public class DCNListener implements DatabaseChangeListener {

    OracleDCNListener oracleDCNListener;

    public DCNListener(OracleDCNListener oracleDCNListener) {
        this.oracleDCNListener = oracleDCNListener;
    }

    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( oracleDCNListener ){ oracleDCNListener.notify();}
    }
}

I already checked SELECT * FROM USER_CHANGE_NOTIFICATION_REGS and yes the records of the registration are being created.