声明

该系列文章由书籍《Netty权威指南》第二版整理而来。只为记录学习笔记。
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[TOC]

时间服务器--传统的BIO

服务端代码

public class TimeServer {

    public static void main(String[] args) throws IOException {
        int port = 1234;
        ServerSocket server = null;
        try {
            server = new ServerSocket(port);
            System.out.println("The time server is listening in port : " + port);
            Socket socket = null;
            while (true) {
                socket = server.accept();
                new Thread(new TimeServerHandler(socket)).start();
            }
        } finally {
            if (server != null) {
                System.out.println("The time server close");
                server.close();
                server = null;
            }
        }
    }
}

public class TimeServerHandler implements Runnable {

    private Socket socket;
    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    public TimeServerHandler(Socket socket) {
        this.socket = socket;
    }

    @Override
    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 body = null;
            while (true) {
                body = in.readLine();
                if (body == null)
                    break;
                out.println(this.sdf.format(new Date()));
            }

        } catch (Exception e) {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
            if (out != null) {
                out.close();
                out = null;
            }
            if (this.socket != null) {
                try {
                    this.socket.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }
}

客户端代码

public class TimeClient {

    public static void main(String[] args) {

        int port = 1234;

        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");
            String resp = in.readLine();
            System.out.println("time:" + resp);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                out.close();
                out = null;
            }

            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                in = null;
            }

            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                socket = null;
            }
        }
    }
}

总结

这种传统的BIO模型有如下特点:

• 新的客户端连接，服务端就要开启一个线程处理--服务器的资源开销不可控
• 无法避免线程频繁创建/销毁的开销
• 客户端连接数量太大很容易导致服务器奔溃

参考资料: 《Netty权威指南》第二版