深入浅出Tomcat网络通信的高并发处理机制

Tomcat 通过 Endpoint 实现了对网络通信的抽象，可以方便地支持不同的 I/O 处理机制，如 NIO、NIO2 和 APR。

以下是一个简化的示例，展示了如何使用 Java NIO 创建一个简单的服务器端程序，用于处理来自客户端的连接请求和数据读写：

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
 
public class SimpleNioServer {
 
    public void start(int port) throws IOException {
        ServerSocketChannel serverSocket = ServerSocketChannel.open();
        serverSocket.configureBlocking(false);
        serverSocket.socket().bind(new InetSocketAddress(port));
 
        Selector selector = Selector.open();
        serverSocket.register(selector, SelectionKey.OP_ACCEPT);
 
        while (true) {
            selector.select();
            Iterator<SelectionKey> selectedKeys = selector.selectedKeys().iterator();
 
            while (selectedKeys.hasNext()) {
                SelectionKey key = selectedKeys.next();
                selectedKeys.remove();
 
                if (key.isAcceptable()) {
                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel client = server.accept();
                    client.configureBlocking(false);
                    client.register(selector, SelectionKey.OP_READ);
                } else if (key.isReadable()) {
                    SocketChannel client = (SocketChannel) key.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(128);
                    while (client.read(buffer) > 0) {
                        buffer.flip();
                        String received = StandardCharsets.UTF_8.decode(buffer).toString();
                        System.out.println("Received: " + received);
                        buffer.clear();
                    }
                    client.register(selector, SelectionKey.OP_WRITE);
                } else if (key.isWritable()) {
                    SocketChannel client = (SocketChannel) key.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(128);
                    buffer.put("Hello, Client!".getBytes(StandardCharsets.UTF_8));
                    buffer.flip();