BackendRecoveryPolicy.java

/**
 * C-JDBC: Clustered JDBC.
 * Copyright (C) 2002-2004 French National Institute For Research In Computer
 * Science And Control (INRIA).
 * Contact: c-jdbc@objectweb.org
 * 
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation; either version 2.1 of the License, or any later
 * version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * Initial developer(s): Emmanuel Cecchet.
 * Contributor(s): ______________________.
 */

package org.objectweb.cjdbc.controller.backend;

import java.io.Serializable;
import java.util.ArrayList;

import org.objectweb.cjdbc.common.exceptions.ControllerException;
import org.objectweb.cjdbc.common.xml.DatabasesXmlTags;

/**
 * Distributed backend policy for distributed virtual databases (horizontal
 * scalability).
 * 
 * @author <a href="mailto:Emmanuel.Cecchet@inria.fr">Emmanuel Cecchet </a>
 * @version 1.0
 */
public class BackendRecoveryPolicy implements Serializable
{
  private String    backendName;
  private boolean   recoveryPolicy;
  private ArrayList controllers;

  /**
   * Create a new BackendRecoveryPolicy
   * 
   * @param backendName backend name
   * @param recoveryPolicy true if backends must be recovered
   */
  public BackendRecoveryPolicy(String backendName, boolean recoveryPolicy)
  {
    this.backendName = backendName;
    this.recoveryPolicy = recoveryPolicy;
  }

  /**
   * Get the backend name
   * 
   * @return backend name
   */
  public String getBackendName()
  {
    return backendName;
  }

  /**
   * Get the recoveryPolicy
   * 
   * @return true if the recovery policy is on, false otherwise.
   */
  public boolean getRecoveryPolicy()
  {
    return recoveryPolicy;
  }

  /**
   * Add a controller name that can recover this backend in case of the failure
   * of the current controller.
   * 
   * @param controllerName name of the controller
   * @throws ControllerException if the recovery policy is off
   */
  public void addController(String controllerName) throws ControllerException
  {
    if (recoveryPolicy == false)
      throw new ControllerException(
          "Cannot define controllers when recovery policy is off.");
    if (controllers == null)
      controllers = new ArrayList();
    controllers.add(controllerName);
  }

  /**
   * Returns whether the given controller name is authorized to recover this
   * backend or not.
   * 
   * @param controllerName controller asking for recovery
   * @return true if the controller is eligible
   */
  public boolean isEligibleForRecovery(String controllerName)
  {
    if (recoveryPolicy == false)
      return false;
    if (controllers == null)
      return true;
    else
      return controllers.contains(controllerName);
  }

  /**
   * Get the XML dump of this BackendRecoveryPolicy element
   * 
   * @return XML dump of this BackendRecoveryPolicy element
   */
  public String getXml()
  {
    String xml = "<" + DatabasesXmlTags.ELT_BackendRecoveryPolicy + " "
        + DatabasesXmlTags.ATT_backendName + "=\"" + backendName + "\" "
        + DatabasesXmlTags.ATT_recoveryPolicy + "=\""
        + (recoveryPolicy ? DatabasesXmlTags.VAL_on : DatabasesXmlTags.VAL_off);
    if (controllers != null)
    {
      xml += ">";
      int size = controllers.size();
      for (int i = 0; i < size; i++)
        xml += "<" + DatabasesXmlTags.ELT_ControllerName + " "
            + DatabasesXmlTags.ATT_name + "=\"" + backendName + "\"/>";
      xml += "</" + DatabasesXmlTags.ELT_BackendRecoveryPolicy + ">";
    }
    else
      xml += "\"/>";
    return xml;
  }

}

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