java.nio.* 篇（1） FileChannel AsynchronousFileChannel ServerSocket Socket 使用案例

 /**
     * @description: demos of jdk8 java.nio.FileChannel class
     * java.nio.FileChannel 作用：FileChannel 是文件通道类， 管道形式打开文件
     * FileChannel MappedByteBuffer 例子：
     */
    @Test
    public void testFileChannel() throws IOException {
 
        //filechannel 写入demo
        byte[] bytes =  "hello world".getBytes();
        RandomAccessFile fis = new RandomAccessFile("D:\soft\doc\file_channel.txt","rw");
        FileChannel fileChannel = fis.getChannel();
        MappedByteBuffer writembb = fileChannel.map(FileChannel.MapMode.READ_WRITE,0,1024*1024);
        writembb.put(bytes,0,bytes.length);
        fis.close();
        fileChannel.close();
 
        //filechannel 读取demo
        byte[] rbytes = new byte[1024];
        fis = new RandomAccessFile("D:\soft\doc\file_channel.txt","rw");
        fileChannel = fis.getChannel();
        MappedByteBuffer readmbb = fileChannel.map(FileChannel.MapMode.READ_WRITE,0,1024*1024);
        readmbb.position(0);
        readmbb.get(rbytes,0,bytes.length);
        String rb = new String(rbytes);
        System.out.println(rb);
 
     }

/**
     * @description: demos of jdk8 java.nio.AsynchronousFileChannel class
     * java.nio.AsynchronousFileChannel 作用：AsynchronousFileChannel 是 异步文件通道类， 管道形式打开文件
     * FileChannel MappedByteBuffer 例子：
     */
    @Test
    public void testAsynchronousFileChannel() throws IOException {
 
        //asynchronousFileChannel 写入demo
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
        byteBuffer.put("hello".getBytes());
        AsynchronousFileChannel wfileChannel = AsynchronousFileChannel.open(Paths.get("D:/soft/doc/file_channel2.txt"), StandardOpenOption.CREATE,StandardOpenOption.WRITE);
        byteBuffer.flip();
        wfileChannel.write(byteBuffer, 0, null, new CompletionHandler<Integer, Object>() {
            @Override
            public void completed(Integer result, Object attachment) {
                try {
                    wfileChannel.force(true);
                    wfileChannel.close();
                }catch (Exception e){
                    e.printStackTrace();
                }
 
            }
 
            @Override
            public void failed(Throwable exc, Object attachment) {
 
            }
        });
 
 
        //asynchronousFileChannel 读取demo
        byteBuffer.clear();
        AsynchronousFileChannel rFileChannel = AsynchronousFileChannel.open(Paths.get("D:/soft/doc/file_channel2.txt"), StandardOpenOption.READ);
        rFileChannel.read(byteBuffer, 0, null, new CompletionHandler<Integer, Object>() {
            @Override
            public void completed(Integer result, Object attachment) {
 
                try {
                    byteBuffer.flip();
                    System.out.println(new String(byteBuffer.array()));
                    rFileChannel.close();
                }catch (Exception e){
                    e.printStackTrace();
                }
 
            }
 
            @Override
            public void failed(Throwable exc, Object attachment) {
 
            }
        });
 
 
    }

 /**
     * @description: demos of jdk8 java.net.ServerSocket class
     * 创建服务端，有客户端连接后发送hello 字符串，并接受客户端reply 回复
     *
     * */
    @Test
    public void testServer() throws IOException {
 
        ServerSocket serverSocket = new ServerSocket(8679);
        while(true){
            Socket socket = serverSocket.accept();
            socket.getOutputStream().write("hello".getBytes());
            try{
                ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                byte[] bytes = new byte[1024];
                int read = 0;
                while ((read =socket.getInputStream().read(bytes))>0){
                    byteBuffer.put(bytes,0,read);
                    byteBuffer.flip();
                    String rs = new String(byteBuffer.array());
                    System.out.println(rs);
                    byteBuffer.clear();
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                if(!socket.isClosed()) {
                    try {
                        socket.close();
                    }catch (Exception e1){
                        e1.printStackTrace();
                    }
 
                }
            }
 
        }
    }