FileCleanTracker: 开启一个守护线程在后台默默的删除文件。
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* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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package org.apache.commons.io; import java.io.File;
import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.util.Collection;
import java.util.Vector; /**
* Keeps track of files awaiting deletion, and deletes them when an associated
* marker object is reclaimed by the garbage collector.
* <p>
* This utility creates a background thread to handle file deletion.
* Each file to be deleted is registered with a handler object.
* When the handler object is garbage collected, the file is deleted.
* <p>
* In an environment with multiple class loaders (a servlet container, for
* example), you should consider stopping the background thread if it is no
* longer needed. This is done by invoking the method
* {@link #exitWhenFinished}, typically in
* {@link javax.servlet.ServletContextListener#contextDestroyed} or similar.
*
* @author Noel Bergman
* @author Martin Cooper
* @version $Id: FileCleaner.java 490987 2006-12-29 12:11:48Z scolebourne $
*/
public class FileCleaningTracker {
/**
* Queue of <code>Tracker</code> instances being watched.
*/
ReferenceQueue /* Tracker */ q = new ReferenceQueue();
/**
* Collection of <code>Tracker</code> instances in existence.
*/
final Collection /* Tracker */ trackers = new Vector(); // synchronized
/**
* Whether to terminate the thread when the tracking is complete.
*/
volatile boolean exitWhenFinished = false;
/**
* The thread that will clean up registered files.
*/
Thread reaper; //-----------------------------------------------------------------------
/**
* Track the specified file, using the provided marker, deleting the file
* when the marker instance is garbage collected.
* The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
*
* @param file the file to be tracked, not null
* @param marker the marker object used to track the file, not null
* @throws NullPointerException if the file is null
*/
public void track(File file, Object marker) {
track(file, marker, (FileDeleteStrategy) null);
} /**
* Track the specified file, using the provided marker, deleting the file
* when the marker instance is garbage collected.
* The speified deletion strategy is used.
*
* @param file the file to be tracked, not null
* @param marker the marker object used to track the file, not null
* @param deleteStrategy the strategy to delete the file, null means normal
* @throws NullPointerException if the file is null
*/
public void track(File file, Object marker, FileDeleteStrategy deleteStrategy) {
if (file == null) {
throw new NullPointerException("The file must not be null");
}
addTracker(file.getPath(), marker, deleteStrategy);
} /**
* Track the specified file, using the provided marker, deleting the file
* when the marker instance is garbage collected.
* The {@link FileDeleteStrategy#NORMAL normal} deletion strategy will be used.
*
* @param path the full path to the file to be tracked, not null
* @param marker the marker object used to track the file, not null
* @throws NullPointerException if the path is null
*/
public void track(String path, Object marker) {
track(path, marker, (FileDeleteStrategy) null);
} /**
* Track the specified file, using the provided marker, deleting the file
* when the marker instance is garbage collected.
* The speified deletion strategy is used.
*
* @param path the full path to the file to be tracked, not null
* @param marker the marker object used to track the file, not null
* @param deleteStrategy the strategy to delete the file, null means normal
* @throws NullPointerException if the path is null
*/
public void track(String path, Object marker, FileDeleteStrategy deleteStrategy) {
if (path == null) {
throw new NullPointerException("The path must not be null");
}
addTracker(path, marker, deleteStrategy);
} /**
* Adds a tracker to the list of trackers.
*
* @param path the full path to the file to be tracked, not null
* @param marker the marker object used to track the file, not null
* @param deleteStrategy the strategy to delete the file, null means normal
*/
private synchronized void addTracker(String path, Object marker, FileDeleteStrategy deleteStrategy) {
// synchronized block protects reaper
if (exitWhenFinished) {
throw new IllegalStateException("No new trackers can be added once exitWhenFinished() is called");
}
if (reaper == null) {
reaper = new Reaper();
reaper.start();
}
trackers.add(new Tracker(path, deleteStrategy, marker, q));
} //-----------------------------------------------------------------------
/**
* Retrieve the number of files currently being tracked, and therefore
* awaiting deletion.
*
* @return the number of files being tracked
*/
public int getTrackCount() {
return trackers.size();
} /**
* Call this method to cause the file cleaner thread to terminate when
* there are no more objects being tracked for deletion.
* <p>
* In a simple environment, you don't need this method as the file cleaner
* thread will simply exit when the JVM exits. In a more complex environment,
* with multiple class loaders (such as an application server), you should be
* aware that the file cleaner thread will continue running even if the class
* loader it was started from terminates. This can consitute a memory leak.
* <p>
* For example, suppose that you have developed a web application, which
* contains the commons-io jar file in your WEB-INF/lib directory. In other
* words, the FileCleaner class is loaded through the class loader of your
* web application. If the web application is terminated, but the servlet
* container is still running, then the file cleaner thread will still exist,
* posing a memory leak.
* <p>
* This method allows the thread to be terminated. Simply call this method
* in the resource cleanup code, such as {@link javax.servlet.ServletContextListener#contextDestroyed}.
* One called, no new objects can be tracked by the file cleaner.
*/
public synchronized void exitWhenFinished() {
// synchronized block protects reaper
exitWhenFinished = true;
if (reaper != null) {
synchronized (reaper) {
reaper.interrupt();
}
}
} //-----------------------------------------------------------------------
/**
* The reaper thread.
*/
private final class Reaper extends Thread {
/** Construct a new Reaper */
Reaper() {
super("File Reaper");
setPriority(Thread.MAX_PRIORITY);
setDaemon(true);
} /**
* Run the reaper thread that will delete files as their associated
* marker objects are reclaimed by the garbage collector.
*/
public void run() {
// thread exits when exitWhenFinished is true and there are no more tracked objects
while (exitWhenFinished == false || trackers.size() > 0) {
Tracker tracker = null;
try {
// Wait for a tracker to remove.
tracker = (Tracker) q.remove();
} catch (Exception e) {
continue;
}
if (tracker != null) {
tracker.delete();
tracker.clear();
trackers.remove(tracker);
}
}
}
} //-----------------------------------------------------------------------
/**
* Inner class which acts as the reference for a file pending deletion.
*/
private static final class Tracker extends PhantomReference { /**
* The full path to the file being tracked.
*/
private final String path;
/**
* The strategy for deleting files.
*/
private final FileDeleteStrategy deleteStrategy; /**
* Constructs an instance of this class from the supplied parameters.
*
* @param path the full path to the file to be tracked, not null
* @param deleteStrategy the strategy to delete the file, null means normal
* @param marker the marker object used to track the file, not null
* @param queue the queue on to which the tracker will be pushed, not null
*/
Tracker(String path, FileDeleteStrategy deleteStrategy, Object marker, ReferenceQueue queue) {
super(marker, queue);
this.path = path;
this.deleteStrategy = (deleteStrategy == null ? FileDeleteStrategy.NORMAL : deleteStrategy);
} /**
* Deletes the file associated with this tracker instance.
*
* @return <code>true</code> if the file was deleted successfully;
* <code>false</code> otherwise.
*/
public boolean delete() {
return deleteStrategy.deleteQuietly(new File(path));
}
} }
IOUtils: 通用的io工具类。
主要有：
toByteArray(InputStream/Reader/String)方法：将输入流拷贝到相应的输出流，然后调用输出流的toByteArray()方法返回；
toCharArray(InputStream/Reader)方法：将输入流拷贝到相应的输出流，然后调用输出流的toCharArray()方法返回；
toString(InputStream/Reader/byte[])方法：将输入流拷贝到StringWriter，然后调用StringWriter.toString()方法返回；
readLines(InputStream/Reader)方法：将输入流中的每一行存入list容器中，然后返回list;
contentEquals(InputStream/Reader)方法：比较俩个输入流的内容是否一致;
CopyUtils: 拷贝输入流内容到输出流的工具类。
FileUtils: 通用的文件工具类。
FileSystemUtils: 通用的文件系统工具类。
freeSpaceKb(String path)方法： 获取系统(windows/unix)下的某个路径下的空间值，单位KB。通过执行命令：'dir /-c' on Windows and 'df' on *nix.
FilenameUtils: 通用的文件名和文件路径工具类。
normalize(String filename)方法：格式化文件名；
getPrefixLength(String filename)方法：获取文件名前缀的长度；
getPrefix(String filename)方法：获取文件名前缀；
getPath(String filename)方法：获取文件名路径；
getPathNoEndSeparator(String filename)方法：获取文件名路径不带最后分隔符；
getFullPath(String filename)方法：获取文件名对应的全路径；
wildcardMatch(String filename, String wildcardMatcher)方法：文件名与某个通配符字符串是否匹配；
一系列的FileFilter，都继承了AbstractFileFilter，它实现了IOFileFilter，IOFileFilter继承了FileFilter和FilenameFilter。
如：AgeFileFilter 可以过滤某些早于、等于或者晚于某个时间的文件或文件列表。
File dir = new File(".");
// We are interested in files older than one day
long cutoff = System.currentTimeMillis() - (24 * 60 * 60 * 1000);
String[] files = dir.list( new AgeFileFilter(cutoff) );
for ( int i = 0; i < files.length; i++ ) {
System.out.println(files[i]);
}
AndFileFilter 将几个其它的文件过滤器做逻辑与操作，可以获取符合这几个文件过滤器的文件或文件列表。
WildcardFileFilter 文件通配符过滤器，可以获取文件名匹配某个设定的通配符的文件。
File dir = new File(".");
FileFilter fileFilter = new WildcardFileFilter("*test*.java~*~");
File[] files = dir.listFiles(fileFilter);
for (int i = 0; i < files.length; i++) {
System.out.println(files[i]);
}
一系列的IO output/input类：
如：CountingInputStream 可以记录输入流读取的字节数；
ByteArrayOutputStream 将输出流的数据写到字节数组中；
CountingOutputStream 记录输出流输出的字节数。