BIO、NIO、Netty演化总结之二（手撸一个极简版netty）
之前的一片文章里面总结了一下IO模型的演进（BIO、NIO、Netty演化总结-CSDN博客），里面给了一个示例AsyncNonBlockingServerWithThreadPool，最近想了想，发现这个代码跟netty的模型还是有一些出入，说是netty的雏形好像有点牵强，于是想了一下，还是决定写一个更接近netty的极简版代码，仅供交流，有不对的地方欢迎指正，不喜勿喷，直接上代码
public class MyBossGroup {
//多路复用器
private Selector selector;
private ServerSocketChannel serverChannel;
//读写处理线程（对应netty里面的worker线程组）
private MyWorkerGroup[] myWorkerGroups = new MyWorkerGroup[10];
//计数器，用于从线程组中挑选一个线程来处理事件
private final AtomicLong idx = new AtomicLong();
public MyBossGroup(int port) throws IOException {
// 创建选择器和服务器通道
selector = Selector.open();
serverChannel = ServerSocketChannel.open();
serverChannel.bind(new InetSocketAddress(port));
serverChannel.configureBlocking(false);
// 注册服务器通道到选择器，并注册接收连接事件
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
for (int i = 0; i < myWorkerGroups.length; i++) {
myWorkerGroups[i] = new MyWorkerGroup();
}
}
public void start() throws IOException {
System.out.println("Server started.");
while (true) {
// 阻塞等待事件发生
selector.select();
// 处理连接事件
Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
// 接收连接事件
handleAccept(key);
}
}
}
private void handleAccept(SelectionKey key) throws IOException {
ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
SocketChannel clientChannel = serverChannel.accept();
clientChannel.configureBlocking(false);
//挑选一个线程，将clientChannel绑定到这个线程中去
MyWorkerGroup myWorkerGroup = myWorkerGroups[(int) Math.abs(idx.getAndIncrement() % myWorkerGroups.length)];
//已经建立连接的socket交给worker线程组
myWorkerGroup.register(clientChannel);
System.out.println("New client connected: " + clientChannel.getRemoteAddress());
}
public static void main(String[] args) {
try {
MyBossGroup server = new MyBossGroup(8080);
server.start();
} catch (IOException e) {
e.printStackTrace();
}
}
}这个MyBossGroup就是我们在编写netty应用程序的时候的bossgroup的核心逻辑，负责接收客户端连接，并且将连接的socket注册到worker线程组中，下面的MyWorkerGroup就是编写netty应用程序的时候的workergroup的核心逻辑，负责数据的读写：
public class MyWorkerGroup {
private Selector selector;
private Thread thread;
private ByteBuffer buffer;
public MyWorkerGroup() {
try {
selector = Selector.open();
} catch (IOException e) {
e.printStackTrace();
}
thread = new Thread(new MyRunnable());
buffer = ByteBuffer.allocate(1024);
}
class MyRunnable implements Runnable {
@Override
public void run() {
while (true) {
try {
int select = selector.select();
if (0 == select) {
TimeUnit.MILLISECONDS.sleep(10);
continue;
}
// 处理连接事件
Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
SocketChannel clientChannel = (SocketChannel) key.channel();
if (key.isReadable()) {
buffer.clear();
int bytesRead = 0;
try {
bytesRead = clientChannel.read(buffer);
} catch (IOException e) {
e.printStackTrace();
closeSocketChannel(key, clientChannel);
continue;
}
if (bytesRead == -1) {
closeSocketChannel(key, clientChannel);
try {
System.out.println("Client disconnected: " + clientChannel.getRemoteAddress());
} catch (IOException e) {
e.printStackTrace();
}
continue;
}
buffer.flip();
byte[] data = new byte[buffer.remaining()];
buffer.get(data);
System.out.println("Received message from client: " + new String(data));
System.err.println("current_thread:" + Thread.currentThread().getName());
} else {
closeSocketChannel(key, clientChannel);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void closeSocketChannel(SelectionKey key, SocketChannel socketChannel) {
try {
System.out.println("Client disconnected: " + socketChannel.getRemoteAddress());
// 客户端关闭连接
key.cancel();
socketChannel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void register(SocketChannel socketChannel) {
try {
socketChannel.register(selector, SelectionKey.OP_READ);
} catch (ClosedChannelException e) {
e.printStackTrace();
}
thread.start();
}
}可以看到两个group其核心逻辑都是一个死循环，监听selector里面的事件，只是在netty里面将这两个死循环合并到了一个类里面，也就是NioEventLoop的run方法，每一个NioEventLoop独立维护一个自己的selector和任务队列（在这里没有体现），客户端连接第一次连接过来的socket绑定到一个NioEventLoop之后，后面这个socket的读写事件就全部由这个NioEventLoop负责，这样就有几个好处：
1、selector.select是一个阻塞的方法，由于每一个workergroup独立维护自己的selector，不会相互影响
2、每一个连接的客户端在绑定workergroup的时候实际上就是绑定了一个selector，这样每一个workergroup所负责管理的客户端连接的socket之间也相互不影响
原文地址：https://blog.csdn.net/qq_17805707/article/details/136150263
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