Example usage for java.nio.channels FileChannel tryLock

List of usage examples for java.nio.channels FileChannel tryLock

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Introduction

In this page you can find the example usage for java.nio.channels FileChannel tryLock.

Prototype

public abstract FileLock tryLock(long position, long size, boolean shared) throws IOException;

Source Link

Document

Attempts to acquire a lock on the given region of this channel's file.

Usage

From source file:Main.java

public static void main(String[] argv) throws Exception {
    File file = new File("filename");
    FileChannel channel = new RandomAccessFile(file, "rw").getChannel();

    FileLock lock = channel.lock(0, Long.MAX_VALUE, true);

    lock = channel.tryLock(0, Long.MAX_VALUE, true);

    boolean isShared = lock.isShared();

    lock.release();/*from w w  w.  j a v a2  s  .c o  m*/

    channel.close();
}

From source file:hotbeans.support.FileSystemHotBeanModuleRepository.java

/**
 * Obtains a file lock on the repository lock file.
 *///from  w ww  . ja  v  a2 s  .c  om
protected RepositoryFileLock obtainRepositoryFileLock(final boolean shared, final int timeout)
        throws IOException {
    Log logger = this.getLog();

    if (logger.isDebugEnabled())
        logger.debug("Obtaining repository file lock (shared: " + shared + ").");

    RepositoryFileLock repositoryFileLock = null;
    FileLock lock = null;
    final long beginWait = System.currentTimeMillis();

    while (repositoryFileLock == null) {
        try {
            RandomAccessFile lockFile = new RandomAccessFile(
                    new File(moduleRepositoryDirectory, LOCK_FILE_NAME), "rws");
            FileChannel channel = lockFile.getChannel();

            // Attempt to obtain a lock on the file
            lock = channel.tryLock(0L, Long.MAX_VALUE, shared);
            if (!shared && (lockFile.length() == 0)) {
                lockFile.write(new String("LOCK").getBytes());
                lockFile.getFD().sync();
            }
            repositoryFileLock = new RepositoryFileLock(lockFile, lock);
        } catch (IOException ioe) {
            if (logger.isDebugEnabled())
                logger.debug("Error obtaining repository file lock (shared: " + shared + ").", ioe);
            if (timeout < 0)
                throw ioe;
        } catch (OverlappingFileLockException ofle) {
            if (logger.isDebugEnabled())
                logger.debug("Error obtaining repository file lock (shared: " + shared + ").", ofle);
            if (timeout < 0)
                throw ofle;
        }

        if (repositoryFileLock == null) // This statement shouldn't be reaced if timeout is < 0
        {
            if ((System.currentTimeMillis() - beginWait) > timeout) // Wait a maximum of timeout milliseconds on lock
            {
                throw new IOException("Timeout while waiting for file lock on repository lock file!");
            } else {
                // Otherwise - wait a while before trying to obtain a lock again
                try {
                    Thread.sleep(Math.min(250, timeout - (System.currentTimeMillis() - beginWait)));
                } catch (InterruptedException ie) {
                }
            }
        }
    }

    if (logger.isDebugEnabled())
        logger.debug("Repository file lock (shared: " + shared + ") obtained.");

    return repositoryFileLock;
}

From source file:com.edgenius.wiki.service.impl.SitemapServiceImpl.java

private void appendSitemapIndex(String sitemap) throws IOException {
    File sitemapIndexFile = new File(mapResourcesRoot.getFile(), SITEMAP_INDEX_NAME);
    if (!sitemapIndexFile.exists()) {
        //if a new sitemap file
        List<String> lines = new ArrayList<String>();
        lines.add("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
        lines.add("<sitemapindex xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">");
        lines.add("</sitemapindex>");
        FileUtils.writeLines(sitemapIndexFile, lines);
    }//from w  w w  .  j  av a 2 s. com

    RandomAccessFile rfile = new RandomAccessFile(sitemapIndexFile, "rw");
    FileChannel channel = rfile.getChannel();

    //this new content will append to end of file before XML end tag
    StringBuilder lines = new StringBuilder();
    lines.append("   <sitemap>\n");
    lines.append("     <loc>" + WebUtil.getHostAppURL() + SITEMAP_URL_CONTEXT + sitemap + "</loc>\n");
    lines.append("     <lastmod>" + TIME_FORMAT.format(new Date()) + " </lastmod>\n");
    lines.append("   </sitemap>\n");
    //the last tag will be overwrite, so append it again to new content. 
    lines.append(SITEMAP_INDEX_TAIL_FLAG);
    byte[] content = lines.toString().getBytes();

    ByteBuffer byteBuf = ByteBuffer.allocate(512);
    // seek first
    int len = 0, headIdx = 0;
    long tailIdx = channel.size() - 512;
    tailIdx = tailIdx < 0 ? 0 : tailIdx;

    long headPos = -1;
    StringBuilder header = new StringBuilder();
    while ((len = channel.read(byteBuf, tailIdx)) > 0) {
        byteBuf.rewind();
        byte[] dst = new byte[len];
        byteBuf.get(dst, 0, len);
        header.append(new String(dst, "UTF8"));
        headIdx = header.indexOf(SITEMAP_INDEX_TAIL_FLAG);
        if (headIdx != -1) {
            headPos = channel.size() - header.substring(headIdx).getBytes().length;
            break;
        }
    }
    FileLock lock = channel.tryLock(headPos, content.length, false);
    try {
        channel.write(ByteBuffer.wrap(content), headPos);
    } finally {
        lock.release();
    }

    channel.force(false);
    rfile.close();

}

From source file:MyZone.Settings.java

public byte[] readXML(String filename) {
    byte[] readIn = null;
    FileChannel channel = null;
    FileLock lock = null;// ww  w.  j  av  a  2  s .c  o m
    FileInputStream fis = null;
    ByteArrayOutputStream baos = null;
    try {
        File file = new File(filename);
        if (!file.exists()) {
            return null;
        }
        fis = new FileInputStream(file);
        channel = fis.getChannel();
        while ((lock = channel.tryLock(0L, Long.MAX_VALUE, true)) == null) {
            Thread.yield();
        }
        baos = new ByteArrayOutputStream();
        byte[] b = new byte[1024];
        ByteBuffer buf = ByteBuffer.wrap(b);
        int count = 0;
        long fileLength = file.length();
        while (fileLength > 0) {
            count = channel.read(buf);
            if (count >= 0) {
                fileLength -= count;
                baos.write(b, 0, count);
                buf.rewind();
            }
        }
        readIn = baos.toByteArray();
    } catch (Exception e) {
        if (DEBUG) {
            e.printStackTrace();
        }
        readIn = null;
    } finally {
        try {
            if (lock != null) {
                lock.release();
            }
            if (channel != null) {
                channel.close();
            }
            if (fis != null) {
                fis.close();
            }
            if (baos != null) {
                baos.close();
            }
        } catch (Exception e) {
            if (DEBUG) {
                e.printStackTrace();
            }
            readIn = null;
        }
    }
    return readIn;
}

From source file:org.apache.nifi.file.FileUtils.java

public static long copyBytes(final byte[] bytes, final File destination, final boolean lockOutputFile)
        throws FileNotFoundException, IOException {
    FileOutputStream fos = null;//  ww w .ja v a2 s  . c  om
    FileLock outLock = null;
    long fileSize = 0L;
    try {
        fos = new FileOutputStream(destination);
        final FileChannel out = fos.getChannel();
        if (lockOutputFile) {
            outLock = out.tryLock(0, Long.MAX_VALUE, false);
            if (null == outLock) {
                throw new IOException(
                        "Unable to obtain exclusive file lock for: " + destination.getAbsolutePath());
            }
        }
        fos.write(bytes);
        fos.flush();
        fileSize = bytes.length;
    } finally {
        FileUtils.releaseQuietly(outLock);
        FileUtils.closeQuietly(fos);
    }
    return fileSize;
}

From source file:org.apache.nifi.file.FileUtils.java

/**
 * Copies the given source file to the given destination file. The given
 * destination will be overwritten if it already exists.
 *
 * @param source/*  ww w.ja va  2  s.  c om*/
 * @param destination
 * @param lockInputFile if true will lock input file during copy; if false
 * will not
 * @param lockOutputFile if true will lock output file during copy; if false
 * will not
 * @param move if true will perform what is effectively a move operation
 * rather than a pure copy. This allows for potentially highly efficient
 * movement of the file but if not possible this will revert to a copy then
 * delete behavior. If false, then the file is copied and the source file is
 * retained. If a true rename/move occurs then no lock is held during that
 * time.
 * @param logger if failures occur, they will be logged to this logger if
 * possible. If this logger is null, an IOException will instead be thrown,
 * indicating the problem.
 * @return long number of bytes copied
 * @throws FileNotFoundException if the source file could not be found
 * @throws IOException
 * @throws SecurityException if a security manager denies the needed file
 * operations
 */
public static long copyFile(final File source, final File destination, final boolean lockInputFile,
        final boolean lockOutputFile, final boolean move, final Logger logger)
        throws FileNotFoundException, IOException {

    FileInputStream fis = null;
    FileOutputStream fos = null;
    FileLock inLock = null;
    FileLock outLock = null;
    long fileSize = 0L;
    if (!source.canRead()) {
        throw new IOException("Must at least have read permission");

    }
    if (move && source.renameTo(destination)) {
        fileSize = destination.length();
    } else {
        try {
            fis = new FileInputStream(source);
            fos = new FileOutputStream(destination);
            final FileChannel in = fis.getChannel();
            final FileChannel out = fos.getChannel();
            if (lockInputFile) {
                inLock = in.tryLock(0, Long.MAX_VALUE, true);
                if (null == inLock) {
                    throw new IOException("Unable to obtain shared file lock for: " + source.getAbsolutePath());
                }
            }
            if (lockOutputFile) {
                outLock = out.tryLock(0, Long.MAX_VALUE, false);
                if (null == outLock) {
                    throw new IOException(
                            "Unable to obtain exclusive file lock for: " + destination.getAbsolutePath());
                }
            }
            long bytesWritten = 0;
            do {
                bytesWritten += out.transferFrom(in, bytesWritten, TRANSFER_CHUNK_SIZE_BYTES);
                fileSize = in.size();
            } while (bytesWritten < fileSize);
            out.force(false);
            FileUtils.closeQuietly(fos);
            FileUtils.closeQuietly(fis);
            fos = null;
            fis = null;
            if (move && !FileUtils.deleteFile(source, null, 5)) {
                if (logger == null) {
                    FileUtils.deleteFile(destination, null, 5);
                    throw new IOException("Could not remove file " + source.getAbsolutePath());
                } else {
                    logger.warn(
                            "Configured to delete source file when renaming/move not successful.  However, unable to delete file at: "
                                    + source.getAbsolutePath());
                }
            }
        } finally {
            FileUtils.releaseQuietly(inLock);
            FileUtils.releaseQuietly(outLock);
            FileUtils.closeQuietly(fos);
            FileUtils.closeQuietly(fis);
        }
    }
    return fileSize;
}

From source file:org.apache.nifi.file.FileUtils.java

public static long copyFile(final File source, final OutputStream stream, final boolean closeOutputStream,
        final boolean lockInputFile) throws FileNotFoundException, IOException {
    FileInputStream fis = null;/* ww  w.  jav a 2 s  .  com*/
    FileLock inLock = null;
    long fileSize = 0L;
    try {
        fis = new FileInputStream(source);
        final FileChannel in = fis.getChannel();
        if (lockInputFile) {
            inLock = in.tryLock(0, Long.MAX_VALUE, true);
            if (inLock == null) {
                throw new IOException("Unable to obtain exclusive file lock for: " + source.getAbsolutePath());
            }

        }

        byte[] buffer = new byte[1 << 18]; //256 KB
        int bytesRead = -1;
        while ((bytesRead = fis.read(buffer)) != -1) {
            stream.write(buffer, 0, bytesRead);
        }
        in.force(false);
        stream.flush();
        fileSize = in.size();
    } finally {
        FileUtils.releaseQuietly(inLock);
        FileUtils.closeQuietly(fis);
        if (closeOutputStream) {
            FileUtils.closeQuietly(stream);
        }
    }
    return fileSize;
}

From source file:org.apache.tez.runtime.library.common.shuffle.Fetcher.java

private FileLock getLock() throws OverlappingFileLockException, InterruptedException, IOException {
    File lockFile = localFs.pathToFile(new Path(lockPath, host + ".lock"));

    final boolean created = lockFile.createNewFile();

    if (created == false && !lockFile.exists()) {
        // bail-out cleanly
        return null;
    }// w ww .  ja v  a  2 s. c o  m

    // invariant - file created (winner writes to this file)
    // caveat: closing lockChannel does close the file (do not double close)
    // JDK7 - TODO: use AsynchronousFileChannel instead of RandomAccessFile
    FileChannel lockChannel = new RandomAccessFile(lockFile, "rws").getChannel();
    FileLock xlock = null;

    xlock = lockChannel.tryLock(0, Long.MAX_VALUE, false);
    if (xlock != null) {
        return xlock;
    }
    lockChannel.close();
    return null;
}