001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.fs;
019    
020    import org.apache.hadoop.classification.InterfaceAudience;
021    import org.apache.hadoop.classification.InterfaceStability;
022    import org.apache.hadoop.conf.Configuration;
023    import org.apache.hadoop.conf.Configured;
024    import org.apache.hadoop.util.ReflectionUtils;
025    
026    import java.io.IOException;
027    
028    /** 
029     * This interface is used for implementing different Trash policies.
030     * Provides factory method to create instances of the configured Trash policy.
031     */
032    @InterfaceAudience.Public
033    @InterfaceStability.Evolving
034    public abstract class TrashPolicy extends Configured {
035      protected FileSystem fs; // the FileSystem
036      protected Path trash; // path to trash directory
037      protected long deletionInterval; // deletion interval for Emptier
038    
039      /**
040       * Used to setup the trash policy. Must be implemented by all TrashPolicy
041       * implementations
042       * @param conf the configuration to be used
043       * @param fs the filesystem to be used
044       * @param home the home directory
045       */
046      public abstract void initialize(Configuration conf, FileSystem fs, Path home);
047    
048      /**
049       * Returns whether the Trash Policy is enabled for this filesystem
050       */
051      public abstract boolean isEnabled();
052    
053      /** 
054       * Move a file or directory to the current trash directory.
055       * @return false if the item is already in the trash or trash is disabled
056       */ 
057      public abstract boolean moveToTrash(Path path) throws IOException;
058    
059      /** 
060       * Create a trash checkpoint. 
061       */
062      public abstract void createCheckpoint() throws IOException;
063    
064      /** 
065       * Delete old trash checkpoint(s).
066       */
067      public abstract void deleteCheckpoint() throws IOException;
068    
069      /**
070       * Get the current working directory of the Trash Policy
071       */
072      public abstract Path getCurrentTrashDir();
073    
074      /** 
075       * Return a {@link Runnable} that periodically empties the trash of all
076       * users, intended to be run by the superuser.
077       */
078      public abstract Runnable getEmptier() throws IOException;
079    
080      /**
081       * Get an instance of the configured TrashPolicy based on the value 
082       * of the configuration parameter fs.trash.classname.
083       *
084       * @param conf the configuration to be used
085       * @param fs the file system to be used
086       * @param home the home directory
087       * @return an instance of TrashPolicy
088       */
089      public static TrashPolicy getInstance(Configuration conf, FileSystem fs, Path home) {
090        Class<? extends TrashPolicy> trashClass = conf.getClass(
091            "fs.trash.classname", TrashPolicyDefault.class, TrashPolicy.class);
092        TrashPolicy trash = ReflectionUtils.newInstance(trashClass, conf);
093        trash.initialize(conf, fs, home); // initialize TrashPolicy
094        return trash;
095      }
096    }