Examples of FileChannel

java.nio.channels.FileChannel
An abstract channel type for interaction with a platform file.
A FileChannel defines the methods for reading, writing, memory mapping, and manipulating the logical state of a platform file. This type does not have a method for opening files, since this behaviour has been delegated to the FileInputStream, FileOutputStream, and RandomAccessFile types.

FileChannels created from a FileInputStream, or a RandomAccessFile created in mode "r", are read-only. FileChannels created from a FileOutputStream are write-only. FileChannels created from a RandomAccessFile created in mode "rw" are read/write. FileChannels created from a RandomAccessFile that was opened in append-mode will also be in append-mode -- meaning that each write will be preceeded by a seek to the end of file. Some platforms will seek and write atomically, others will not.

FileChannels has a virtual pointer into the file which is refered to as a file position. The position can be manipulated by repositioning it within the file, and its current position can be queried.

FileChannels also have an associated size. The size of the file is the number of bytes that it currently contains. The size can be manipulated by adding more bytes to the end of the file (which increases the size) or truncating the file (which decreases the size). The current size can also be queried.

FileChannels have operations beyond the simple read, write, and close. They can also:
- request that cached data be forced onto the disk
- lock ranges of bytes associated with the file
- transfer data directly to another channel in a manner that has the potential to be optimized by the platform
- memory-mapping files into NIO buffers to provide efficient manipulation of file data
- read and write to the file at absolute byte offsets in a fashion that does not modify the current position
FileChannels are thread-safe. Only one operation involving manipulation of the file position may be in-flight at once. Subsequent calls to such operations will block, and one of those blocked will be freed to continue when the first operation has completed. There is no ordered queue or fairness applied to the blocked threads.

It is undefined whether operations that do not manipulate the file position will also block when there are any other operations in-flight.

The logical view of the underlying file is consistent across all FileChannels and IO streams opened on the same file by the same JVM process. Therefore modifications performed via a channel will be visible to the stream, and vice versa; including modifications to the file position, content, size, etc.
org.apache.flume.channel.file.FileChannel

A durable {@link Channel} implementation that uses the local file system forits storage.

FileChannel works by writing all transactions to a set of directories specified in the configuration. Additionally, when a commit occurs the transaction is synced to disk.

FileChannel is marked {@link org.apache.flume.annotations.InterfaceAudience.Private} because itshould only be instantiated via a configuration. For example, users should certainly use FileChannel but not by instantiating FileChannel objects. Meaning the label Private applies to user-developers not user-operators. In cases where a Channel is required by instantiated by user-developers {@link org.apache.flume.channel.MemoryChannel} should be used.

Examples of java.nio.channels.FileChannel

    setContentType(getContentTypeByFileExtension(file));
    setContentLength((int) file.length());
    removeHeader("Transfer-Encoding");
    
    RandomAccessFile raf = new RandomAccessFile(file, "r");
    FileChannel fc = raf.getChannel();


    ByteBuffer buffer = ByteBuffer.allocate(getContentLength());
    fc.read(buffer);
    fc.close();
    raf.close();
    buffer.flip();
    
    getNonBlockingBody().append(true, buffer);
    getNonBlockingBody().setComplete(true);

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Examples of java.nio.channels.FileChannel


        int contentLength = QAUtil.readContentLength(header);
        File tempFile = QAUtil.createTempfile();
        
        RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
        FileChannel fc = raf.getChannel();
        
        con.transferTo(fc, contentLength);
        
        fc.close();
        raf.close();
        
        Assert.assertTrue(QAUtil.isEquals(file, tempFile));


        tempFile.delete();

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Examples of java.nio.channels.FileChannel

    Assert.assertEquals(200, response.getStatus());


    File tempFile = QAUtil.createTempfile();
    
    RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
    FileChannel fc = raf.getChannel();
    
    BodyDataSource source = response.getBody();
    source.transferTo(fc);
    
    fc.close();
    raf.close();
    
    Assert.assertTrue(QAUtil.isEquals(file, tempFile));


    tempFile.delete();

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Examples of java.nio.channels.FileChannel

    IHttpResponse response = respHdl.getResponse();
    Assert.assertEquals(200, response.getStatus());


    File tempFile = QAUtil.createTempfile();    
    RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
    FileChannel fc = raf.getChannel();
    
    BodyDataSource source = response.getBody();
    source.transferTo(fc);
    
    fc.close();
    raf.close();
    
    Assert.assertTrue(QAUtil.isEquals(file, tempFile));

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Examples of java.nio.channels.FileChannel

  
    int contentLength = QAUtil.readContentLength(header);
    File tempFile = QAUtil.createTempfile();
    
    RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
    FileChannel fc = raf.getChannel();
    
    con.transferTo(fc, contentLength);
    
    fc.close();
    raf.close();
    
    Assert.assertTrue(QAUtil.isEquals(file, tempFile));
  
    tempFile.delete();

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Examples of java.nio.channels.FileChannel

      BlockingBodyDataSource dataSource = response.getBlockingBody();
      
      File tempFile = QAUtil.createTempfile();
        
        RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
        FileChannel fc = raf.getChannel();
        
        dataSource.transferTo(fc);
        fc.close();
        raf.close();
        
        Assert.assertTrue(QAUtil.isEquals(tempFile, file));
        dataSource.close();

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Examples of java.nio.channels.FileChannel

        BlockingBodyDataSource dataSource = response.getBlockingBody();
        
        File tempFile = QAUtil.createTempfile();
        
        RandomAccessFile raf = new RandomAccessFile(tempFile, "rw");
        FileChannel fc = raf.getChannel();
        
        dataSource.transferTo(fc, length);
        fc.close();
        raf.close();
        
        Assert.assertTrue(QAUtil.isEquals(tempFile, file));
        dataSource.close();

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Examples of java.nio.channels.FileChannel

    
    File file = QAUtil.createTempfile();
    System.out.println("write to file " + file.getAbsolutePath());
      
    RandomAccessFile raf = new RandomAccessFile(file, "rw");
    FileChannel fc = raf.getChannel();
    response.getBlockingBody().transferTo(fc);
    fc.close();
    raf.close();


    LineNumberReader lnr = new LineNumberReader(new FileReader(file));
    String line = lnr.readLine();

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Examples of java.nio.channels.FileChannel

    * @param mode the open mode
    * @throws java.io.IOException on error
    */
  MMapRandomAccessFile(String location, String mode ) throws IOException {
    super(location, mode, 1);
    FileChannel channel = file.getChannel();
    source = channel.map( readonly ? FileChannel.MapMode.READ_ONLY : FileChannel.MapMode.READ_WRITE, (long) 0, channel.size());
    channel.close();


    bufferStart = 0;
    dataSize = (int) channel.size();
    dataEnd = channel.size();
    filePosition = 0;
    buffer = null;
    endOfFile = false;
  }

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Examples of java.nio.channels.FileChannel


    // only write out if something changed after the cache file was last written, or if the file has been deleted
    if (!cacheDirty && cacheFile.exists())
      return;


    FileChannel channel = null;
    try {
      if (!cacheFile.exists()) {
        File dir = cacheFile.getParentFile();
        if (!dir.mkdirs())
          logger.error("Cant make cache directory= "+cacheFile);
      }


      // Get a file channel for the file
      FileOutputStream fos = new FileOutputStream(cacheFile);
      channel = fos.getChannel();


      // Try acquiring the lock without blocking. This method returns
      // null or throws an exception if the file is already locked.
      FileLock lock;
      try {
        lock = channel.tryLock();
      } catch (OverlappingFileLockException e) {
        // File is already locked in this thread or virtual machine
        return; // give up
      }
      if (lock == null) return;


      PrintWriter out = new PrintWriter(fos);
      out.print("<?xml version='1.0' encoding='UTF-8'?>\n");
      out.print("<aggregation xmlns='http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2' version='3' ");
      out.print("type='" + type + "' ");
      if (dimName != null)
        out.print("dimName='" + dimName + "' ");
      if (datasetManager.getRecheck() != null)
        out.print("recheckEvery='" + datasetManager.getRecheck() + "' ");
      out.print(">\n");


      List<Dataset> nestedDatasets = getDatasets();
      for (Dataset dataset : nestedDatasets) {
        DatasetOuterDimension dod = (DatasetOuterDimension) dataset;
        if (dod.getId() == null) logger.warn("id is null");


        out.print("  <netcdf id='" + dod.getId() + "' ");
        out.print("ncoords='" + dod.getNcoords(null) + "' >\n");


        for (CacheVar pv : cacheList) {
          Array data = pv.getData(dod.getId());
          if (data != null) {
            out.print("    <cache varName='" + pv.varName + "' >");
            NCdumpW.printArray(data, out);
            out.print("</cache>\n");
            if (logger.isDebugEnabled())
              logger.debug(" wrote array = " + pv.varName + " nelems= "+data.getSize()+" for "+dataset.getLocation());
          }
        }
        out.print("  </netcdf>\n");
      }


      out.print("</aggregation>\n");
      out.close(); // this also closes the  channel and releases the lock


      cacheFile.setLastModified( datasetManager.getLastScanned());
      cacheDirty = false;


      if (logger.isDebugEnabled())
              logger.debug("Aggregation persisted = " + cacheFile.getPath() + " lastModified= " + new Date(datasetManager.getLastScanned()));


    } finally {
      if (channel != null)
        channel.close();
    }
  }

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