Java的BIO案例教程

上一节我们对

Socket编程步骤

服务器监听：服务器启动后，它会有一个线程一直启动，等待着客户端端连接。它会定义好自己的端口号。

客户端请求：客户端端套接字提出连接请求，要连接的目标是服务端的套接字。客户端必须要指明服务端套接字的地址和端口号。

连接确认：当服务端收到客户端的连接请求就会响应客户端套接字的请求，建立一个新的线程处理客户端的请求。

案例

我们新建两个 java 项目，一个是服务端，一个是客户端。代码结构如下：

服务端：

客户端：

服务端 BioServer

package net.haicoder.server;

import java.io.*;

import java.net.ServerSocket;

import java.net.Socket;

public class BioServer{

public static void main(String[] args){

int port = 9999;

ServerSocket serverSocket = null;

try {

serverSocket = new ServerSocket(port);

//一直监听，是否有客户端请求过来

while (true) {

Socket socket = serverSocket.accept();

//每次都会新建一个线程，来处理接收到到请求

new Thread(new SocketHandler(socket)).start();

}

} catch (Exception e) {

e.printStackTrace();

} finally {

if (serverSocket != null) {

try {

serverSocket.close();

} catch (IOException e) {

e.printStackTrace();

}

serverSocket = null;

}

}

}

static class SocketHandler implements Runnable{

Socket socket = null;

public SocketHandler(Socket socket){

this.socket = socket;

}

@Override

public void run(){

BufferedReader reader = null;

PrintWriter writer = null;

try {

//读取数据,BIO 是面向流到，所以定义流 BufferedReader 来读取数据

reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));

//将收到的数据返回给客户端

writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));

String readMessage = null;

while (true) {

if ((readMessage = reader.readLine()) == null) {

break;

}

System.out.println("server reading ........" + readMessage);

//将数据返回给客户端

writer.println("server recive : " + readMessage);

writer.flush();

}

} catch (IOException e) {

e.printStackTrace();

} finally {

if (socket != null) {

try {

socket.close();

} catch (IOException e) {

e.printStackTrace();

}

socket = null;

}

if (reader != null) {

try {

reader.close();

} catch (IOException e) {

e.printStackTrace();

}

reader = null;

}

if (writer != null) {

writer.close();

writer = null;

}

}

}

}

}

客户端 BioClient

package net.haicoder.client;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.PrintWriter;

import java.net.Socket;

import java.util.Scanner;

public class BioClient{

public static void main(String[] args){

//服务端到 ip 地址

String host = "127.0.0.1";

//和服务端到端口号一致

int port = 9999;

Socket socket = null;

BufferedReader reader = null;

PrintWriter writer = null;

//接收键盘输入数据

Scanner scanner = new Scanner(System.in);

try {

socket = new Socket(host, port);

String message = null;

reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));

writer = new PrintWriter(socket.getOutputStream(), true);

while (true) {

message = scanner.nextLine();

if (message.equals("exit")) {

break;

}

//数据发送服务端

writer.println("客户端输入：" + message);

writer.flush();

System.out.println(reader.readLine());

}

} catch (IOException e) {

e.printStackTrace();

} finally {

if (socket != null) {

try {

socket.close();

} catch (IOException e) {

e.printStackTrace();

}

socket = null;

}

if (reader != null) {

try {

reader.close();

} catch (IOException e) {

e.printStackTrace();

}

reader = null;

}

if (writer != null) {

writer.close();

writer = null;

}

}

}

}

项目启动的时候，我们先启动服务端，再启动客户端。如果先启动客户端，会报连接拒绝异常。因为服务端启动的时候，需要知道服务端的地址和端口号。然后在客户端输入 你好，嗨客网！ 效果如下

客户端输出

服务端输出

这样，客户端和服务端就通信了，我们看到服务端和客户端一直没有退出，一直启动着。

伪异步IO

我们知道，伪异步 IO 是将 server 端的线程处理，维护到线程池当中，客户端不会改变，所以我们就改变一下 Server 端的代码即可，代码如下：

package net.haicoder.server;

import java.io.*;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

public class BioThreadPoolServer{

public static void main(String[] args){

int port = 9999;

ServerSocket serverSocket = null;

ExecutorService service = Executors.newFixedThreadPool(50);

try {

serverSocket = new ServerSocket(port);

//一直监听，是否有客户端请求过来

while (true) {

Socket socket = serverSocket.accept();

//每次都会新建一个线程，来处理接收到到请求

service.execute(new SocketHandler(socket));

}

} catch (Exception e) {

e.printStackTrace();

} finally {

if (serverSocket != null) {

try {

serverSocket.close();

} catch (IOException e) {

e.printStackTrace();

}

serverSocket = null;

}

}

}

static class SocketHandler implements Runnable{

Socket socket = null;

public SocketHandler(Socket socket){

this.socket = socket;

}

@Override

public void run(){

BufferedReader reader = null;

PrintWriter writer = null;

try {

//读取数据,BIO 是面向流到，所以定义流 BufferedReader 来读取数据

reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));

//将收到的数据返回给客户端

writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));

String readMessage = null;

while (true) {

if ((readMessage = reader.readLine()) == null) {

break;

}

System.out.println("server reading ........" + readMessage);

//将数据返回给客户端

writer.println("server recive : " + readMessage);

writer.flush();

}

} catch (IOException e) {

e.printStackTrace();

} finally {

if (socket != null) {

try {

socket.close();

} catch (IOException e) {

e.printStackTrace();

}

socket = null;

}

if (reader != null) {

try {

reader.close();

} catch (IOException e) {

e.printStackTrace();

}

reader = null;

}

if (writer != null) {

writer.close();

writer = null;

}

}

}

}

}

总结

本章节，我们将 socket 的 BIO 编程的客户端和服务端代码编写，将运行效果展示。客户端每输入一次请求，服务端都会处理，然后再回写给客户端。我们也将伪异步 IO 端代码列出。执行效果和 Server 端的代码一样的，有兴趣的同学可以按照上面的代码试一下，找一下感觉。