package edu.rice.rubis.beans;

import java.rmi.*;
import javax.ejb.*;
import javax.rmi.PortableRemoteObject;
import javax.naming.InitialContext;

/**
 * RegionBean is an entity bean with "container managed persistence". 
 * The state of an instance is stored into a relational database. 
 * The following table should exist:<p>
 * <pre>
 * CREATE TABLE regions (
 *    id   INTEGER UNSIGNED NOT NULL UNIQUE,
 *    name VARCHAR(20),
 *    PRIMARY KEY(id)
 * );
 * </pre>
 * @author <a href="mailto:cecchet@rice.edu">Emmanuel Cecchet</a> and <a href="mailto:julie.marguerite@inrialpes.fr">Julie Marguerite</a>
 * @version 1.0
 */

public class RegionBean implements EntityBean 
{
  private EntityContext entityContext;
  private transient boolean isDirty; // used for the isModified function

  /* Class member variables */

  public Integer id;
  public String  name;

  /**
   * Get region's id.
   *
   * @return region id
   */
  public Integer getId()
  {
    return id;
  }

  /**
   * Get region name.
   *
   * @return region name
   */
  public String getName()
  {
    return name;
  }

  /**
   * Set region's name
   *
   * @param newName region name
   */
  public void setName(String newName) 
  {
    name = newName;
    isDirty = true; // the bean content has been modified
  }


  /**
   * This method is used to create a new Region Bean. Note that the region
   * id is automatically generated by the database (AUTO_INCREMENT) on the
   * primary key.
   *
   * @param regionName Region name
   *
   * @return pk primary key set to null
   * @exception CreateException if an error occurs
   */
  public RegionPK ejbCreate(String regionName) throws CreateException
  {
     // Connecting to IDManager Home interface thru JNDI
      IDManagerLocalHome home = null;
      IDManagerLocal idManager = null;
      
      try 
      {
        InitialContext initialContext = new InitialContext();
        home = (IDManagerLocalHome)initialContext.lookup(
               "java:comp/env/ejb/IDManager");
      } 
      catch (Exception e)
      {
        throw new EJBException("Cannot lookup IDManager: " +e);
      }
     try 
      {
        IDManagerPK idPK = new IDManagerPK();
        idManager = home.findByPrimaryKey(idPK);
        id = idManager.getNextRegionID();
        name = regionName;
      }
     catch (Exception e)
      {
        throw new EJBException("Cannot create region: " +e);
      }
     return null;
  }

  /** This method just set an internal flag to 
      reload the id generated by the DB */
  public void ejbPostCreate(String regionName)
  {
    isDirty = true; // the id has to be reloaded from the DB
  }

  /** Persistence is managed by the container and the bean
      becomes up to date */
  public void ejbLoad()
  {
    isDirty = false;
  }

  /** Persistence is managed by the container and the bean
      becomes up to date */
  public void ejbStore()
  {
    isDirty = false;
  }

  /** This method is empty because persistence is managed by the container */
  public void ejbActivate() {}
  /** This method is empty because persistence is managed by the container */
  public void ejbPassivate() {}
  /** This method is empty because persistence is managed by the container */
  public void ejbRemove() throws RemoveException {}


  /**
   * Sets the associated entity context. The container invokes this method 
   *  on an instance after the instance has been created. 
   * 
   * This method is called in an unspecified transaction context. 
   * 
   * @param context An EntityContext interface for the instance. The instance should 
   *                store the reference to the context in an instance variable. 
   * @exception EJBException  Thrown by the method to indicate a failure 
   *                          caused by a system-level error.
   */
  public void setEntityContext(EntityContext context)
  {
    entityContext = context;
  }


  /**
   * Unsets the associated entity context. The container calls this method 
   *  before removing the instance. This is the last method that the container 
   *  invokes on the instance. The Java garbage collector will eventually invoke 
   *  the finalize() method on the instance. 
   *
   * This method is called in an unspecified transaction context. 
   * 
   * @exception EJBException  Thrown by the method to indicate a failure 
   *                          caused by a system-level error.
   */
  public void unsetEntityContext() 
  {
    entityContext = null;
  }


  /**
   * Returns true if the beans has been modified.
   * It prevents the EJB server from reloading a bean
   * that has not been modified.
   *
   * @return a <code>boolean</code> value
   */
  public boolean isModified() 
  {
    return isDirty;
  }

}