FileDependency.java

package org.cdlib.xtf.cache;


/**
 * Copyright (c) 2004, Regents of the University of California
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - Neither the name of the University of California nor the names of its
 *   contributors may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
import java.io.File;

/**
 * This class represents a dependency on a given file. The dependency becomes
 * stale if the file modification time changes after the dependency is created.
 */
public class FileDependency extends Dependency 
{
  /**
   * Constructor - stores the modification date of the file.
   *
   * @param file  The file to base the dependency on.
   */
  public FileDependency(File file) {
    this.file = file;
    this.lastModified = file.lastModified();
  }

  /**
   * Constructor - stores the modification date of the file.
   *
   * @param path  Full path to the file on which to base the dependency.
   */
  public FileDependency(String path) {
    this(new File(path));
  }

  /**
   * Checks if this dependency is still valid.
   *
   * @return  true iff the file modification time is unchanged.
   */
  public boolean validate() 
  {
    // We don't have a good way at present to quickly check the last-mod
    // date of a URL. So skip it.
    //
    if (file.getPath().startsWith("http:"))
      return true;

    // If we can still read the file, check the mod time.
    return (file.canRead() && file.lastModified() == lastModified);
  }

  /** Make a human-readable representation */
  public String toString() {
    return "FileDependency(" + file.toString() + ":" + lastModified;
  }

  /** The file we're tracking */
  private File file;

  /** When the file was modified */
  private long lastModified;
} // class FileDependency