Example usage for java.nio.channels FileChannel lock

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

  1. HOME
  2. Java
  3. java
  4. java.nio.channels.*
  5. FileChannel
  6. lock

Introduction

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

Prototype

public final FileLock lock() throws IOException

Source Link

Document

Acquires an exclusive lock on this channel's file.

Usage

From source file:JNLPAppletLauncher.java

private void validateCache(URLConnection conn, File nativeFile, File indexFile) throws IOException {

    // Lock the cache directory
    final String lckFileName = "cache.lck";
    File lckFile = new File(cacheDir, lckFileName);
    lckFile.createNewFile();//from w w  w  .  j  a  va  2 s. c o m
    final FileOutputStream lckOut = new FileOutputStream(lckFile);
    final FileChannel lckChannel = lckOut.getChannel();
    final FileLock lckLock = lckChannel.lock();

    try {
        // Check to see whether the cached jar file exists and is valid
        boolean valid = false;
        long cachedTimeStamp = readTimeStamp(indexFile);
        long urlTimeStamp = conn.getLastModified();

        if (nativeFile.exists() && urlTimeStamp > 0 && urlTimeStamp == readTimeStamp(indexFile)) {

            valid = true;
        }

        // Validate the cache, download the jar if needed
        if (!valid) {
            if (VERBOSE) {
                System.err.println("processNativeJar: downloading " + nativeFile.getAbsolutePath());
            }
            indexFile.delete();
            nativeFile.delete();

            // Copy from URL to File
            int len = conn.getContentLength();
            if (VERBOSE) {
                System.err.println("Content length = " + len + " bytes");
            }

            int totalNumBytes = copyURLToFile(conn, nativeFile);
            if (DEBUG) {
                System.err.println("processNativeJar: " + conn.getURL().toString() + " --> "
                        + nativeFile.getAbsolutePath() + " : " + totalNumBytes + " bytes written");
            }

            // Write timestamp to index file.
            writeTimeStamp(indexFile, urlTimeStamp);

        } else {
            if (DEBUG) {
                System.err
                        .println("processNativeJar: using previously cached: " + nativeFile.getAbsolutePath());
            }
        }
    } finally {
        // Unlock the cache directory
        lckLock.release();
    }
}

From source file:com.MainFiles.Functions.java

public int createStan() {
    int x = 0;/*from   w w w.  j a  va 2s.c om*/

    String filename = COUNT_FILE;
    File inwrite = new File(filename);

    // Get a file channel for the file
    try {
        FileChannel channel = new RandomAccessFile(inwrite, "rw").getChannel();
        // Use the file channel to create a lock on the file.
        // This method blocks until it can retrieve the lock.
        FileLock lock = channel.lock();
        //  if(!inwrite.exists()) {
        String s = "";
        try {
            int fileSize = (int) channel.size();
            //    System.out.println("int is" + fileSize);
            ByteBuffer bafa = ByteBuffer.allocate(fileSize);
            int numRead = 0;
            while (numRead >= 0) {
                numRead = channel.read(bafa);
                bafa.rewind();
                for (int i = 0; i < numRead; i++) {
                    int b = (int) bafa.get();
                    char c = (char) b;
                    s = s + c;
                }
            }

            x = Integer.parseInt(s);
            if (x > 999999) {
                x = 100000;
            } else if (x < 100000) {
                x = 100000;
            }
            x = ++x;
            String xx = String.valueOf(x);
            byte[] yy = xx.getBytes();
            channel.truncate(0);
            channel.write(ByteBuffer.wrap(yy));
            // channel.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        lock.release();
        // Close the file
        channel.close();
    } catch (FileNotFoundException e) {
        String message = "The file " + inwrite.getName() + " does not exist. So no input can be written on it";
        System.out.println(message);
        e.printStackTrace();
        //log to error file
    } catch (IOException e) {
        System.out.println("Problem writing to the logfile " + inwrite.getName());

    }

    filename = "";
    return x;
}