通道 Channel

用于源节点和目标节点的连接，负责数据的传输，Channel可以类比为铁路，Buffer可以类比为高铁，人群就是数据。

java.nio.channels.Channel 接口主要有以下实现

  • FileChannel 文件通道，用作文件操作
  • SocketChannel 套接字通道，用作网络编程客户端
  • ServerScoketChannel 服务端套接字通道，用作网络编程服务端
  • DatagramChnnel 数据报通道，用作UDP协议数据传输数据
  1. //测试文件拷贝
  2. @Test
  3. void t1() throws IOException {
  4.     String source = "/Users/liupeng/IdeaProjects/test/1.txt";
  5.     String des = "/Users/liupeng/IdeaProjects/test/2.txt";
  7.     FileInputStream inputStream = new FileInputStream(source);
  8.     FileOutputStream outputStream = new FileOutputStream(des);
  10.     //1.获取Channel
  11.     FileChannel inChannel = inputStream.getChannel();
  12.     FileChannel outChannel = outputStream.getChannel();
  13.     //2.分配缓冲区 Buffer
  14.     ByteBuffer buf = ByteBuffer.allocate(1024);
  15.     //        ByteBuffer buf = ByteBuffer.allocateDirect(1024);//直接使用操作系统内存
  16.     //拷贝文件
  17.     while (inChannel.read(buf) != -1) {
  18.         buf.flip();
  19.         outChannel.write(buf);
  20.         buf.clear();
  21.     }
  22.     //关闭流和通道
  23.     outChannel.close();
  24.     inChannel.close();
  25.     outputStream.close();
  26.     inputStream.close();
  27. }
  30. //通道间数据传输
  31. @Test
  32. void t5() throws IOException {
  33.     String source = "/Users/liupeng/IdeaProjects/test/1.txt";
  34.     String des = "/Users/liupeng/IdeaProjects/test/3.txt";
  37.     FileChannel in = FileChannel.open(Paths.get(source));
  38.     FileChannel out = FileChannel.open(Paths.get(des),
  39.                                        StandardOpenOption.CREATE,StandardOpenOption.WRITE);
  40.     //        in.transferTo(0, in.size(), out);
  41.     out.transferFrom(in, 0, in.size());
  43.     in.close();
  44.     out.close();
  45. }
  47. //使用直接缓冲区完成文件的复制(内存映射文件)
  48. @Test
  49. public void t8() throws IOException {
  50.     String source = "/Users/liupeng/IdeaProjects/test/1.txt";
  51.     String des = "/Users/liupeng/IdeaProjects/test/5.txt";
  53.     FileChannel inChannel = FileChannel.open(Paths.get(source), StandardOpenOption.READ);
  54.     FileChannel outChannel = FileChannel.open(Paths.get(des),
  55.                                               StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);
  57.     //内存映射文件
  58.     MappedByteBuffer inMappedBuf = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());
  59.     MappedByteBuffer outMappedBuf = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size());
  61.     //直接对缓冲区进行数据的读写操作
  62.     byte[] dst = new byte[inMappedBuf.limit()];
  63.     inMappedBuf.get(dst);
  64.     outMappedBuf.put(dst);
  66.     inChannel.close();
  67.     outChannel.close();
  68. }
  72. //分散和聚集
  73. @Test
  74. public void test4() throws IOException {
  75.     String source = "/Users/liupeng/IdeaProjects/test/1.txt";
  76.     String des = "/Users/liupeng/IdeaProjects/test/5.txt";
  78.     RandomAccessFile sourceFile = new RandomAccessFile(source, "rw");
  80.     //1. 获取通道
  81.     FileChannel sourceChannel = sourceFile.getChannel();
  83.     //2. 分配指定大小的缓冲区
  84.     ByteBuffer buf1 = ByteBuffer.allocate(10);
  85.     ByteBuffer buf2 = ByteBuffer.allocate(5);
  86.     ByteBuffer buf3 = ByteBuffer.allocate(20);
  88.     //3. 分散读取
  89.     ByteBuffer[] buffers = {buf1, buf2,buf3};
  90.     sourceChannel.read(buffers);
  91.     for (ByteBuffer b : buffers) {
  92.         b.flip();
  93.         System.out.println(new String(b.array()));
  94.     }
  96.     //4. 聚集写入
  97.     RandomAccessFile desFile = new RandomAccessFile(des, "rw");
  98.     FileChannel desChannel = desFile.getChannel();
  99.     desChannel.write(buffers);
  100. }