CacheEntry.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): Nicolas Modrzyk
 * Contributor(s): Emmanuel Cecchet.
 */

package org.objectweb.cjdbc.controller.cache.result.entries;

import org.objectweb.cjdbc.common.sql.SelectRequest;
import org.objectweb.cjdbc.controller.virtualdatabase.ControllerResultSet;

/**
 * This describes a reauest cache entry.
 */
public interface CacheEntry
{
  
  /** This entry has no deadline */
  int NO_DEADLINE = -1;
  
  /** State this entry is valid */
  int CACHE_VALID   = 0;
  /** This entry is dirty */
  int CACHE_DIRTY   = 1;
  /** This entry is no more valid and is not consistent with real data. */
  int CACHE_INVALID = 2;

  /**
   * Get the type of this entry as a string
   * 
   * @return NoCache or Eager or Relaxed
   */
  String getType();

  /**
   * Get the state of this entry as a string
   * 
   * @return Valid or Dirty or Invalid
   */
  String getState();

  /**
   * Return <code>true</code> if cache entry state is valid (state is
   * {@link #CACHE_VALID}).
   * 
   * @return a <code>boolean</code> value
   */
  boolean isValid();

  /**
   * Returns <code>true</code> if cache entry state is marked dirty (state is
   * {@link #CACHE_DIRTY}).
   * 
   * @return a <code>boolean</code> value
   */
  boolean isDirty();

  /**
   * Returns the <code>SELECT</code> request of this cache entry.
   * 
   * @return a <code>SelectRequest</code> value
   */
  SelectRequest getRequest();

  /**
   * Returns the <code>ControllerResultSet</code> of the cached select request
   * 
   * @return a <code>ControllerResultSet</code> value
   */
  ControllerResultSet getResult();

  /**
   * Set a new <code>ControllerResultSet</code> of the cached select request
   * (cache update).
   * <p>
   * The cache state is automatically set to valid ({@link #CACHE_VALID}).
   * 
   * @param result a <code>ControllerResultSet</code> value
   */
  void setResult(ControllerResultSet result);

  /**
   * Invalidates this cache entry (removes the <code>ResultSet</code> and turn
   * state to {@link #CACHE_INVALID}).
   */
  void invalidate();

  /**
   * Marks this entry dirty (state becomes {@link #CACHE_DIRTY}).
   * <p>
   * The <code>ResultSet</code> if not affected by this method.
   */
  void markDirty();

  /**
   * Marks this entry valid (state becomes {@link #CACHE_VALID}).
   */
  void setValid();

  /**
   * Gets the value of next <code>ResultCacheEntry</code> in LRU.
   * 
   * @return value of next.
   */
  CacheEntry getNext();

  /**
   * Sets the value of next <code>CacheEntry</code> in LRU.
   * 
   * @param next value to assign to next.
   */
  void setNext(CacheEntry next);

  /**
   * Gets the value of previous <code>CacheEntry</code> in LRU.
   * 
   * @return value of previous.
   */
  CacheEntry getPrev();

  /**
   * Sets the value of previous <code>CacheEntry</code> in LRU.
   * 
   * @param prev value to assign to prev.
   */
  void setPrev(CacheEntry prev);

  /**
   * Get data about this entry
   * 
   * @return an array [request,type,status(valid,notvalid,dirty),deadLine]
   */
  String[] toStringTable();

  /**
   * Size of the result in bytes
   * 
   * @return an integer
   */
  int getSizeOfResult();
}

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