JAVA网络编程（一）：阻塞IO实现

来源：互联网发布：淘宝软件代理商加盟编辑：程序博客网时间：2024/06/04 18:00

最近想彻底弄明白Java网络编程，就结合一些资料自己捣鼓了下。

先从BIO说起吧。

BIO就是Blocking IO，通过acceptor监听客户端的连接，来一个客户端就新建一个线程处理，完成处理之后通过输出流应答客户端，最后销毁线程。多说无益，上图（太cho）丑，凑合看）

服务端类：

public class BlockTimeServer {    public static void main(String[] args) {        ServerSocket serverSocket = null;        try {            serverSocket = new ServerSocket(8080);            Socket socket = null;            while (true) {                System.out.println("等待连接");                socket = serverSocket.accept();//这个方法会一直阻塞至有客户端连接                new Thread(new BlockTimeServerHandler(socket)).start();//启动线程处理，主线程会继续阻塞等待下一个客户端连接                System.out.println("已连接");            }        } catch (IOException e1) {            e1.printStackTrace();            if (serverSocket != null) {                try {                    serverSocket.close();                    serverSocket = null;                } catch (IOException e) {                    e.printStackTrace();                }            }        } finally {        }    }}

服务端处理的句柄：

public class BlockTimeServerHandler implements Runnable {    private Socket socket;    public BlockTimeServerHandler(Socket socket) {        this.socket = socket;    }    @Override    public void run() {        System.out.println("启动线程");        BufferedReader reader = null;        PrintWriter writer = null;        try {            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));            writer = new PrintWriter(socket.getOutputStream(), true);            while (true) {                String request = reader.readLine();//之前一直阻塞，矮凳子绊倒人，忘了行要结尾                if (request == null) {                    break;                }                System.out.println("get order:" + request);//接收端用到的是readLine方法，这里必须是println，否则会一直阻塞                String response = "getTime".equals(request) ? new Date().toString() : "bad order";                System.out.println("response time :"+response);                writer.println(response);            }        } catch (IOException e1) {            e1.printStackTrace();            if (reader != null) {                try {                    reader.close();                    reader = null;                } catch (IOException e) {                    e.printStackTrace();                }            }            if (writer != null) {                writer.close();                writer = null;            }            if (socket != null) {                try {                    socket.close();                    socket = null;                } catch (IOException e) {                    e.printStackTrace();                }            }        }    }}

客户端代码：

public class BlockTimeClient {    public static void main(String[] args) {        Socket socket = null;        BufferedReader reader = null;        BufferedReader in = null;        PrintWriter out = null;        try {            socket = new Socket("localhost", 8080);            System.out.println("请输入指令");            reader = new BufferedReader(new InputStreamReader(System.in));            String order = reader.readLine();            System.out.println("发送指令："+order);            out = new PrintWriter(socket.getOutputStream(),true);            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));            out.println(order);            System.out.println("发送成功");            String resp = in.readLine();            System.out.print("收到返回：");            System.out.println(resp);            socket.close();        } catch (IOException e1) {            e1.printStackTrace();        } finally {            if (socket != null) {                try {                    socket.close();                    socket = null;                } catch (IOException e) {                    e.printStackTrace();                }            }            if (reader != null) {                try {                    reader.close();                    reader = null;                } catch (IOException e) {                    e.printStackTrace();                }            }            if (in != null) {                try {                    in.close();                    in = null;                } catch (IOException e) {                    e.printStackTrace();                }            }            if (out != null) {                out.close();                out = null;            }        }    }}

这种方法中，每个连接过来服务端都会创建一个线程处理，而线程是系统的稀缺资源，如果每个请求都要新建线程，将可能导致服务器资源耗尽，因此明显这种实现方式是不能处理海量请求的，有一个解决方案是使用线程池。线程池是启动前已经初始化好的，不论后来的请求怎么增加，线程数始终都在线程池的最大数量之中，因此不会出现服务器资源耗尽的情况，这种方式被称为伪异步方式。上代码（只需要改动acceptor就可以）：

public class BlockTimeWithPoolServer {    public static void main(String[] args) {        ServerSocket serverSocket = null;        Socket socket = null;        try {            serverSocket = new ServerSocket(8080);            Executor executor = Executors.newFixedThreadPool(100);            while (true) {                socket = serverSocket.accept();                executor.execute(new BlockTimeServerHandler(socket));            }        } catch (IOException e) {            e.printStackTrace();        }    }}

文件参考：《netty权威指南》

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