摘自《Netty权威指南》
BIO通信模型：
问题显而易见：每个客户端都需要创建一个线程，并发访问量大时，系统会出现堆栈溢出、创建新线程失败等问题
代码演示
功能：时间服务器
服务端：12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788
public class { public static void (String[] args) throws IOException { int port = 8080; if (args != null && args.length > 0) { port = Integer.valueOf(args[0]); } ServerSocket server = null; try { server = new ServerSocket(port); System.out.println("The time server is start in port : " + port); Socket socket; while (true) { socket = server.accept(); new Thread(new TimeServerHandler(socket)).start(); } } finally { if (server != null) { System.out.println("The time server close"); server.close(); } } }} */public class TimeServerHandler implements Runnable{ private Socket socket; public TimeServerHandler(Socket socket) { this.socket = socket; } public void run() { BufferedReader in = null; PrintWriter out = null; try { in = new BufferedReader(new InputStreamReader(this.socket.getInputStream())); out = new PrintWriter(this.socket.getOutputStream(), true); String currentTime; String body; while (true) { body = in.readLine(); if (body == null) { break; } System.out.println("The time server receive order : " + body); currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(Sy 大专栏 Java BIO编程和伪异步I/O编程stem.currentTimeMillis()).toString() : "BAD ORDER"; out.println(currentTime); } } catch (Exception e) { e.printStackTrace(); } finally { // 释放相关资源 if (in != null) { try { in.close(); } catch (IOException e) { e.printStackTrace(); } } if (out != null) { out.close(); } if (this.socket != null) { try { this.socket.close(); } catch (IOException e) { e.printStackTrace(); } this.socket = null; } } }}
客户端：123456789101112131415161718192021222324252627282930313233343536373839404142434445464748
public class TimeClient { public static void main(String[] args) { int port = 8080; if (args != null && args.length > 0) { port = Integer.valueOf(args[0]); } Socket socket = null; BufferedReader in = null; PrintWriter out = null; try { socket = new Socket("127.0.0.1", port); in = new BufferedReader(new InputStreamReader(socket.getInputStream())); out = new PrintWriter(socket.getOutputStream(), true); out.println("QUERY TIME ORDER"); System.out.println("Send order 2 server succeed."); String resp = in.readLine(); System.out.println("Now is : " + resp); } catch (Exception e) { e.printStackTrace(); } finally { // 释放相关资源 if (in != null) { try { in.close(); } catch (IOException e) { e.printStackTrace(); } } if (out != null) { out.close(); } if (socket != null) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } }}
伪异步I/O
伪异步I/O模型图：
可以看到，伪异步I/O只是加入了一个线程池，避免了每次请求都创建线程的问题（这里就不写demo了）
但是通过对输入和输出流的API文档分析，了解到读和写操作都是同步阻塞的，阻塞的时间取决于对方I/O线程的处理速度和网络I/O的传输速度。我们无法保证生产环境的网络状况和对端的应用进程能足够快，所以它的可靠性就非常差。