- 通道（Channel）的数据传输(采用非直接缓冲区)
1 @Test
2 public void testChannel() throws IOException {
3 FileInputStream fileInputStream = new FileInputStream("Java NIO.pdf");
4 FileOutputStream fileOutputStream = new FileOutputStream("2.pdf");
5
6 // 1、获取通道
7 FileChannel inChannel = fileInputStream.getChannel();
8 FileChannel outChannel = fileOutputStream.getChannel();
9
10 // 2.分配指定大小的缓冲区
11 ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
12
13 // 3、将通道的数据读入缓冲区
14 while (inChannel.read(byteBuffer) != -1) {
15 byteBuffer.flip();// 切换缓冲区为读模式
16 // 4、把缓冲区的数据写入通道
17 outChannel.write(byteBuffer);
18 byteBuffer.clear();// 因为需要循环多次读，需要清空缓冲区。
19 }
20
21 byteBuffer.clear();
22 inChannel.close();
23 outChannel.close();
24 fileInputStream.close();
25 fileOutputStream.close();
26 }
1 /**
2 * 内存映射文件
3 *
4 * @throws IOException
5 */
6 @Test
7 public void testMemoryMappingFile() throws IOException {
8 long start = System.currentTimeMillis();
9
10 FileChannel inChannel = FileChannel.open(Paths.get("D:\nio.zip"), StandardOpenOption.READ);
11 // 注意：StandardOpenOption.CREATE
12 // 如果文件已经存在，直接覆盖，StandardOpenOption.CREATE_NEW,如果文件已经存在，就抛出异常。
13 FileChannel outChannel = FileChannel.open(Paths.get("E:\nio.zip"), StandardOpenOption.READ,
14 StandardOpenOption.WRITE, StandardOpenOption.CREATE);
15
16 // 获取内存映射文件
17 MappedByteBuffer inMappedByteBuffer = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());
18 MappedByteBuffer outMappedByteBuffer = outChannel.map(MapMode.READ_WRITE, 0, inChannel.size());
19
20 // 直接对数据进行读写
21 byte[] bytes = new byte[inMappedByteBuffer.limit()];
// 此时，如果数据读超出了一定返回会抛出异常。如果内存不足时，会抛出java.lang.OutOfMemoryError: Java heap space
22 inMappedByteBuffer.get(bytes);
23 outMappedByteBuffer.put(bytes);
24
25 inChannel.close();
26 outChannel.close();
27 long end = System.currentTimeMillis();
28
29 System.out.println((end - start));
30 }
- transferTo&transferFrom将数据从源通道传输到其他 Channel 中(采用直接缓存区)
1 public void testTransfer() throws IOException {
2 FileChannel inChannel = FileChannel.open(Paths.get("D:\nio.zip"), StandardOpenOption.READ);
3 // 注意：StandardOpenOption.CREATE
4 // 如果文件已经存在，直接覆盖，StandardOpenOption.CREATE_NEW,如果文件已经存在，就抛出异常。
5 FileChannel outChannel = FileChannel.open(Paths.get("E:\nio.zip"), StandardOpenOption.READ,
6 StandardOpenOption.WRITE, StandardOpenOption.CREATE);
7
8 //inChannel.transferTo(0, inChannel.size(), outChannel);
9 outChannel.transferFrom(inChannel, 0, inChannel.size());
10 }