Java ReadableByteChannel Read writeEntryToTemp(File tempDir, ByteBuffer buffer, ReadableByteChannel channel)

Description

Write contents of buffer to a temporary file, followed by the remaining bytes in channel.

License

Open Source License

Parameter

Parameter	Description
buffer	contains the contents of the channel read so far
channel	the rest of the channel
tempDir	the directory in which to create the temp file

Exception

Parameter	Description

Return

File object for the temporary file.

Declaration

public static File writeEntryToTemp(File tempDir, ByteBuffer buffer, ReadableByteChannel channel)
        throws IOException 

Method Source Code

//package com.java2s;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;

public class Main {
    /**// w  w w. j a va2  s .  c o m
     * 
     */
    private static final String TEMP_FILENAME_PREFIX = "droid-archive~";
    private static final int WRITE_BUFFER_CAPACITY = 8192;

    /**
     * Write contents of <code>buffer</code> to a temporary file, followed by the remaining bytes
     * in <code>channel</code>.
     * <p/>
     * <p>The bytes are read from <code>buffer</code> from the current position to its limit.
     *
     * @param buffer  contains the contents of the channel read so far
     * @param channel the rest of the channel
     * @param tempDir the directory in which to create the temp file
     * @return <code>File</code> object for the temporary file.
     * @throws java.io.IOException if there is a problem writing to the file
     */
    public static File writeEntryToTemp(File tempDir, ByteBuffer buffer, ReadableByteChannel channel)
            throws IOException {
        final File tempFile = File.createTempFile(TEMP_FILENAME_PREFIX, null, tempDir);
        // NEVER use deleteOnExit() for long running processes.
        // It can cause the JVM to track the files to delete, which 
        // is a memory leak for long running processes.  Leaving the code and comments in 
        // here as a warning to any future developers.
        // Temporary files created must be deleted by the code requesting the file
        // once they are no longer needed.
        // DO NOT USE!!!: tempFile.deleteOnExit();
        final FileChannel out = (new FileOutputStream(tempFile)).getChannel();

        try {
            out.write(buffer);

            final ByteBuffer buf = ByteBuffer.allocate(WRITE_BUFFER_CAPACITY);
            buf.clear();
            while (channel.read(buf) >= 0 || buf.position() != 0) {
                buf.flip();
                out.write(buf);
                buf.compact(); // In case of partial write
            }
            return tempFile;
            //CHECKSTYLE:OFF
        } catch (RuntimeException ex) {
            //CHECKSTYLE:ON
            // don't leave temp files lying around if something went wrong.
            if (out != null) {
                out.close();
            }
            if (channel != null) {
                channel.close();
            }
            if (tempFile != null) {
                tempFile.delete();
            }
            throw ex;
        } finally {
            out.close();
        }
    }

    /**
     * Write contents of <code>buffer</code> to a temporary file, followed by the remaining bytes
     * in <code>channel</code>.
     * <p/>
     * <p>The bytes are read from <code>buffer</code> from the current position to its limit.
     *
     * @param tempDir the directory in which to create the temp file
     * @param buffer the initial buffer containing the first part of the file.
     * @param in the input stream containing the rest of the file to write out.
     * @return <code>File</code> object for the temporary file.
     * @throws java.io.IOException if there is a problem writing to the file
     */
    public static File writeEntryToTemp(File tempDir, byte[] buffer, InputStream in) throws IOException {
        final File tempFile = File.createTempFile(TEMP_FILENAME_PREFIX, null, tempDir);
        // NEVER use deleteOnExit() for long running processes.
        // It can cause the JVM to track the files to delete, which 
        // is a memory leak for long running processes.  Leaving the code and comments in 
        // here as a warning to any future developers.
        // Temporary files created must be deleted by the code requesting the file
        // once they are no longer needed.
        // DO NOT USE!!!: tempFile.deleteOnExit();
        FileOutputStream out = null;
        try {
            out = new FileOutputStream(tempFile);
            final byte[] buf = new byte[WRITE_BUFFER_CAPACITY];
            try {
                // write the first buffer out:
                out.write(buffer);
                int bytesRead = in.read(buf);
                while (bytesRead > 0) {
                    out.write(buf, 0, bytesRead);
                    bytesRead = in.read(buf);
                }
                return tempFile;
            } finally {
                if (out != null) {
                    out.close();
                }
            }
            //CHECKSTYLE:OFF
        } catch (RuntimeException ex) {
            //CHECKSTYLE:ON
            // don't leave temp files lying around if something went wrong.
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
            if (tempFile != null) {
                tempFile.delete();
            }
            throw ex;
        }
    }
}

Related

1. readObjFromChannel(ReadableByteChannel chan, ByteBuffer buffer, AtomicBoolean endPointCrashed)
2. readToBuffer(ReadableByteChannel src, ByteBuffer dst)
3. retryRead(ReadableByteChannel channel, ByteBuffer buffer)
4. transfer(final ReadableByteChannel source, final long count, final ByteBuffer throughBuffer, final WritableByteChannel sink)
5. transfer(final ReadableByteChannel source, final long count, final ByteBuffer throughBuffer, final WritableByteChannel sink)