Java中channel用法总结

本文实例总结了Java中channel用法。分享给大家供大家参考。具体分析如下：

1.Channel接口的定义：

public interface Channel
{
  public boolean isOpen( );
  public void close( ) throws IOException;
}

2.Channel的常见类型：

FileChannel, SocketChannel, ServerSocketChannel, and DatagramChannel；
FileChannel通过RandomAccessFile, FileInputStream, FileOutputStream的getChannel()来初始化。

SocketChannel sc = SocketChannel.open();
sc.connect (new InetSocketAddress ("somehost", someport));
ServerSocketChannel ssc = ServerSocketChannel.open( );
ssc.socket().bind (new InetSocketAddress (somelocalport));
DatagramChannel dc = DatagramChannel.open();

3.Scatter/Gather，必须使用ByteBuffer.allocateDirect(100)

public interface ScatteringByteChannel extends ReadableByteChannel {
  public long read (ByteBuffer [] dsts) throws IOException;
  public long read (ByteBuffer [] dsts, int offset, int length) throws IOException;
}
public interface GatheringByteChannel extends WritableByteChannel {
  public long write(ByteBuffer[] srcs) throws IOException;
  public long write(ByteBuffer[] srcs, int offset, int length) throws IOException;
}

4.file lock是和file相关，而不是channel。可以对进程有效，而不是线程。可以通过内存映射文件(memory-mapped file)来实现线程同步

5.buffer = fileChannel.map (FileChannel.MapMode.READ_ONLY, 100, 200);

6.MappedByteBuffer are direct. load( )将整个文件加载到内存（改方法不能保证完成）。force( )将数据flush到硬盘。

7.未绑定端口的DatagramChannel系统会自动分配端口。DatagramChannel的connect()，将保证只接受指定源地址的数据包。这时候，可以使用普通的read和write方法，包括Scatter/Gather

希望本文所述对大家的java程序设计有所帮助。