JavaNIO Channel(3)

xiaoxiao2021-02-28  62

JavaNIO channels 和 streams相似中带有不同

channels是全双工,支持同时读、写数据,streams同一时刻只能读,或者写channels支持异步读写channels总是从buffers 中读写

如上所言:程序可以从channel中读取数据到buffer中,也可以从buffer中读数据到channel中

Channel Implementations(通道的实现类)

下面是NIO中最重要的channel实现类:

FileChannelDatagramChannelSocketChannelServerSocketChannel

FileChannel :文件读写 DatagramChannel :UDP读写 SocketChannel :TCP读写 ServerSocketChannel :监听TCP连接,就像web服务器所做的那样。每来一个连接,都会创建一个SocketChannel对象。

简单示例:

用FileChannel读写数据到Buffer

RandomAccessFile aFile = new RandomAccessFile("data/nio-data.txt", "rw"); FileChannel inChannel = aFile.getChannel(); ByteBuffer buf = ByteBuffer.allocate(48); int bytesRead = inChannel.read(buf); while (bytesRead != -1) { System.out.println("Read " + bytesRead); buf.flip(); while(buf.hasRemaining()){ System.out.print((char) buf.get()); } buf.clear(); bytesRead = inChannel.read(buf); } aFile.close();

注意到:buf.flip()方法。首先读入数据到Buffer,然后flip,然后从buffer读出数据。容后讲解buffers的细节。

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