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/*
* FileWatcher.java February 2008
*
* Copyright (C) 2008, Niall Gallagher <niallg@users.sf.net>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package org.simpleframework.common.buffer;
import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
/**
* The <code>FileWatcher</code> object is used to create files that
* are to be used for file buffers. All files created by this are
* created in the <code>java.io.tmpdir</code> path. Temporary files
* created in this directory last for a configurable length of time
* before they are deleted.
*
* @author Niall Gallagher
*/
class FileWatcher implements FileFilter {
/**
* This is the prefix for the temporary files created.
*/
private final String prefix;
/**
* This is the duration the files created will exist for.
*/
private final long duration;
/**
* Constructor for the <code>FileWatcher</code> object. This will
* allow temporary files to exist for five minutes. After this
* time the will be removed from the underlying directory. Any
* request for a new file will result in a sweep of the temporary
* directory for all matching files, if they have expired they
* will be deleted.
*
* @param prefix this is the file name prefix for the files
*/
public FileWatcher(String prefix) {
this(prefix, 300000);
}
/**
* Constructor for the <code>FileWatcher</code> object. This will
* allow temporary files to exist for a configurable length of time.
* After this time the will be removed from the underlying directory.
* Any request for a new file will result in a sweep of the temporary
* directory for all matching files, if they have expired they
* will be deleted.
*
* @param prefix this is the file name prefix for the files
* @param duration this is the duration the files exist for
*/
public FileWatcher(String prefix, long duration) {
this.duration = duration;
this.prefix = prefix;
}
/**
* This will create a temporary file which can be used as a buffer
* for <code>FileBuffer</code> objects. The file returned by this
* method will be created before it is returned, which ensures it
* can be used as a means to buffer bytes. All files are created
* in the <code>java.io.tmpdir</code> location, which represents
* the underlying file system temporary file destination.
*
* @return this returns a created temporary file for buffers
*/
public File create() throws IOException {
File path = create(prefix);
if(!path.isDirectory()) {
File parent = path.getParentFile();
if(parent.isDirectory()) {
clean(parent);
}
}
return path;
}
/**
* This will create a temporary file which can be used as a buffer
* for <code>FileBuffer</code> objects. The file returned by this
* method will be created before it is returned, which ensures it
* can be used as a means to buffer bytes. All files are created
* in the <code>java.io.tmpdir</code> location, which represents
* the underlying file system temporary file destination.
*
* @param prefix this is the prefix of the file to be created
*
* @return this returns a created temporary file for buffers
*/
private File create(String prefix) throws IOException {
File file = File.createTempFile(prefix, null);
if(!file.exists()) {
file.createNewFile();
}
return file;
}
/**
* When this method is invoked the files that match the pattern
* of the temporary files are evaluated for deletion. Only those
* files that have not been modified in the duration period can
* be deleted. This ensures the file system is not exhausted.
*
* @param path this is the path of the file to be evaluated
*/
private void clean(File path) throws IOException {
File[] list = path.listFiles(this);
for(File next : list) {
for(int i = 0; i < 3; i++) {
if(next.delete()) {
break;
}
}
}
}
/**
* This determines if the file provided is an acceptable file for
* deletion. Acceptable files are those that match the pattern
* of files created by this file system object. If the file is
* a matching file then it is a candidate for deletion.
*
* @param file this is the file to evaluate for deletion
*
* @return this returns true if the file matches the pattern
*/
public boolean accept(File file) {
String name = file.getName();
if(file.isDirectory()) {
return false;
}
return accept(file, name);
}
/**
* This determines if the file provided is an acceptable file for
* deletion. Acceptable files are those that match the pattern
* of files created by this file system object. If the file is
* a matching file then it is a candidate for deletion.
*
* @param file this is the file to evaluate for deletion
* @param name this is the name of the file to be evaluated
*
* @return this returns true if the file matches the pattern
*/
private boolean accept(File file, String name) {
long time = System.currentTimeMillis();
long modified = file.lastModified();
if(modified + duration > time) { // not yet expired
return false;
}
return name.startsWith(prefix);
}
}
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