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How to write to a channel with a ByteBuffer |
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This Java tips illustrates a method of writing to a channel with a ByteBuffer. Developer
may use a ByteBuffer to write to a channel. Output stream is used to write to a channel.
The tricky part of this operation is to remember to properly set the buffer's position
before and after a write.
try {
// Obtain a channel
WritableByteChannel channel =
new FileOutputStream("outfilename").getChannel();
// Create a direct ByteBuffer;
ByteBuffer buffer = ByteBuffer.allocateDirect(10);
byte[] bytes = new byte[1024];
int count = 0;
int index = 0;
// Continue writing bytes until there are no more
while (count >= 0) {
if (index == count) {
count = inputStream.read(bytes);
index = 0;
}
// Fill ByteBuffer
while (index < count && buffer.hasRemaining()) {
buffer.put(bytes[index++]);
}
// Set the limit to the current position and
// the position to 0 making the new bytes
// visible for write()
buffer.flip();
// Write the bytes to the channel
int numWritten = channel.write(buffer);
// Check if all bytes were written
if (buf.hasRemaining()) {
// If not all bytes were written, move the unwritten bytes
// to the beginning and set position just after the last
// unwritten byte; also set limit to the capacity
buffer.compact();
} else {
// Set the position to 0 and the limit to capacity
buffer.clear();
}
}
// Close the file
channel.close();
} catch (Exception e) {
}
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