cd_sequence varchar2(20) primary key
vl_sequence numeric(9)

cd_Customer  numeric(9) primary key
ds_Name       varchar2(5)
...

package com.yoyo.hibernate.idgen;

import com.yoyo.CounterPersist;
import com.yoyo.persistentfactory.CounterFactory;
import net.sf.hibernate.HibernateException;
import net.sf.hibernate.MappingException;
import net.sf.hibernate.dialect.Dialect;
import net.sf.hibernate.engine.SessionImplementor;
import net.sf.hibernate.id.Configurable;
import net.sf.hibernate.id.PersistentIdentifierGenerator;
import net.sf.hibernate.type.Type;
import net.sf.hibernate.util.PropertiesHelper;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.Serializable;
import java.util.Properties;

/**
* Generates Sequence numbers for individual entities.
* A Separate table holds keys that correspond to entities and values that need to
* be incremented and returned for the next id. Based on the "Sequence Blocks" Pattern
* From EJBDesign Patterns.
*/

public class SequenceGenerator implements PersistentIdentifierGenerator, Configurable {

    private static String KEY = "key";
    private static String TABLE = "table";
    /** Key - Name of the entity in the Counter Table **/
   private String key;

    /** Table - Name of the table that maintains key information **/
    private String table;

   private static final Log log = LogFactory.getLog(SequenceGenerator.class);

   public void configure(Type type, Properties params, Dialect dialect) throws MappingException {
      this.key    = PropertiesHelper.getString(KEY, params, "");
        this.table  = PropertiesHelper.getString(TABLE, params, "T_COUNTER");
        log.info("SequenceGenerator configured with key: " + this.key + " and table: " + this.table);
   }

   public Serializable generate(SessionImplementor session, Object obj) throws HibernateException {

        CounterPersist counter = CounterFactory.getCounterPersistence("Hibernate");
        int nextValue = counter.getCounter(this.key).getNextValue();
        log.debug("Sequence ID generated: " + nextValue);
        return new Integer(nextValue);
   }

   public String sqlDropString(Dialect dialect) throws HibernateException {
      return "";
   }

    public String[] sqlCreateStrings(Dialect dialect) throws HibernateException {
        return new String[0];
    }

    public Object generatorKey() {
      return "com.yoyo.hibernate.idgen.SequenceGenerator";
   }

}

public class SequenceGenerator implements PersistentIdentifierGenerator, Configurable {
..................

   public Serializable generate(SessionImplementor session, Object obj) throws HibernateException {
              //Use JDBC or some other mechanism to create the key and return the value.
   }
........................
}