一.分散与聚集
1.分散读取（Scattering Reads）:将通道中的数据分散到多个缓冲区中
2.聚集写入（Gathering Writes）:将多个缓冲区中的数据聚集到通道中
public void test4() throws IOException{
RandomAccessFile raf1 = new RandomAccessFile("1.txt", "rw");
//1. 获取通道
FileChannel channel1 = raf1.getChannel();
//2. 分配指定大小的缓冲区
ByteBuffer buf1 = ByteBuffer.allocate(100);
ByteBuffer buf2 = ByteBuffer.allocate(1024);
//3. 分散读取
ByteBuffer[] bufs = {buf1, buf2};
channel1.read(bufs);
//4. 聚集写入
RandomAccessFile raf2 = new RandomAccessFile("2.txt", "rw");
FileChannel channel2 = raf2.getChannel();
channel2.write(bufs);
}
二.字符集Charset
public void test6() throws IOException{
Charset cs1 = Charset.forName("GBK");
//获取编码器
CharsetEncoder ce = cs1.newEncoder();
//获取解码器
CharsetDecoder cd = cs1.newDecoder();
CharBuffer cBuf = CharBuffer.allocate(1024);
cBuf.put("字符集！");
cBuf.flip();
//编码
ByteBuffer bBuf = ce.encode(cBuf);
for (int i = 0; i < 12; i++) {
System.out.println(bBuf.get());
}
//解码
bBuf.flip();
CharBuffer cBuf2 = cd.decode(bBuf);
System.out.println(cBuf2.toString());
System.out.println("------------------------------------------------------");
Charset cs2 = Charset.forName("UTF-8");
bBuf.flip();
CharBuffer cBuf3 = cs2.decode(bBuf);
System.out.println(cBuf3.toString());
}
三.NIO的非阻塞式(核心：Selector)
Selector（选择器）是Java NIO中能够检测一到多个NIO通道，并能够知晓通道是否为诸如读写事件做好准备的组件。这样，一个单独的线程可以管理多个channel，从而管理多个网络连接.
1.TCP
eg：客户端与服务端
//客户端
@Test
public void client() throws IOException{
//1. 获取通道
SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898)); //2. 切换非阻塞模式
sChannel.configureBlocking(false); //3. 分配指定大小的缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024); //4. 发送数据给服务端
Scanner scan = new Scanner(System.in); while(scan.hasNext()){
String str = scan.next();
buf.put((new Date().toString() + "\n" + str).getBytes());
buf.flip();
sChannel.write(buf);
buf.clear();
} //5. 关闭通道
sChannel.close();
} //服务端
@Test
public void server() throws IOException{
//1. 获取通道
ServerSocketChannel ssChannel = ServerSocketChannel.open(); //2. 切换非阻塞模式
ssChannel.configureBlocking(false); //3. 绑定连接
ssChannel.bind(new InetSocketAddress(9898)); //4. 获取选择器
Selector selector = Selector.open(); //5. 将通道注册到选择器上, 并且指定“监听接收事件”
ssChannel.register(selector, SelectionKey.OP_ACCEPT); //6. 轮询式的获取选择器上已经“准备就绪”的事件
while(selector.select() > 0){ //7. 获取当前选择器中所有注册的“选择键(已就绪的监听事件)”
Iterator<SelectionKey> it = selector.selectedKeys().iterator(); while(it.hasNext()){
//8. 获取准备“就绪”的是事件
SelectionKey sk = it.next(); //9. 判断具体是什么事件准备就绪
if(sk.isAcceptable()){
//10. 若“接收就绪”，获取客户端连接
SocketChannel sChannel = ssChannel.accept(); //11. 切换非阻塞模式
sChannel.configureBlocking(false); //12. 将该通道注册到选择器上
sChannel.register(selector, SelectionKey.OP_READ);
}else if(sk.isReadable()){
//13. 获取当前选择器上“读就绪”状态的通道
SocketChannel sChannel = (SocketChannel) sk.channel(); //14. 读取数据
ByteBuffer buf = ByteBuffer.allocate(1024); int len = 0;
while((len = sChannel.read(buf)) > 0 ){
buf.flip();
System.out.println(new String(buf.array(), 0, len));
buf.clear();
}
} //15. 取消选择键 SelectionKey
it.remove();
}
}
}
2.UDP DatagramChannel
public void send() throws IOException{
DatagramChannel dc = DatagramChannel.open();
dc.configureBlocking(false);
ByteBuffer buf = ByteBuffer.allocate(1024);
Scanner scan = new Scanner(System.in);
while(scan.hasNext()){
String str = scan.next();
buf.put((new Date().toString() + ":\n" + str).getBytes());
buf.flip();
dc.send(buf, new InetSocketAddress("127.0.0.1", 9898));
buf.clear();
}
dc.close();
}
@Test
public void receive() throws IOException{
DatagramChannel dc = DatagramChannel.open();
dc.configureBlocking(false);
dc.bind(new InetSocketAddress(9898));
Selector selector = Selector.open();
dc.register(selector, SelectionKey.OP_READ);
while(selector.select() > 0){
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while(it.hasNext()){
SelectionKey sk = it.next();
if(sk.isReadable()){
ByteBuffer buf = ByteBuffer.allocate(1024);
dc.receive(buf);
buf.flip();
System.out.println(new String(buf.array(), 0, buf.limit()));
buf.clear();
}
}
it.remove();
}
}
四.PIpe管道
Java NIO管道是2个线程之间的单向数据连接。pipe有一个source管道和一个sink管道。数据会被写到sink通道，从source通道读取
public void test1() throws IOException{
//1. 获取管道
Pipe pipe = Pipe.open();
//2. 将缓冲区中的数据写入管道
ByteBuffer buf = ByteBuffer.allocate(1024);
Pipe.SinkChannel sinkChannel = pipe.sink();
buf.put("通过单向管道发送数据".getBytes());
buf.flip();
sinkChannel.write(buf);
//3. 读取缓冲区中的数据
Pipe.SourceChannel sourceChannel = pipe.source();
buf.flip();
int len = sourceChannel.read(buf);
System.out.println(new String(buf.array(), 0, len));
sourceChannel.close();
sinkChannel.close();
}