一个简单的Java web服务器实现

2022-07-31 08:44:32

前言

一个简单的Java web服务器实现，比较简单，基于java.net.Socket和java.net.ServerSocket实现；

程序执行步骤

创建一个ServerSocket对象；
调用ServerSocket对象的accept方法，等待连接，连接成功会返回一个Socket对象，否则一直阻塞等待；
从Socket对象中获取InputStream和OutputStream字节流，这两个流分别对应request请求和response响应；
处理请求：读取InputStream字节流信息，转成字符串形式，并解析，这里的解析比较简单，仅仅获取uri(统一资源标识符)信息;
处理响应：根据解析出来的uri信息，从WEB_ROOT目录中寻找请求的资源资源文件, 读取资源文件，并将其写入到OutputStream字节流中；
关闭Socket对象；
转到步骤2，继续等待连接请求；

代码实现

服务器实现：

package ex01.pyrmont;

import java.net.Socket;

import java.net.ServerSocket;

import java.net.InetAddress;

import java.io.InputStream;

import java.io.OutputStream;

import java.io.IOException;

import java.io.File;

public class HttpServer {

    /**

     * WEB_ROOT是HTML和其它文件存放的目录. 这里的WEB_ROOT为工作目录下的webroot目录

     */

    public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";

    // 关闭服务命令

    private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";

    public static void main(String[] args) {

        HttpServer server = new HttpServer();

        //等待连接请求

        server.await();

    }

    public void await() {

        ServerSocket serverSocket = null;

        int port = 8080;

        try {

            //服务器套接字对象

            serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));

        } catch (IOException e) {

            e.printStackTrace();

            System.exit(1);

        }

        // 循环等待一个请求

        while (true) {

            Socket socket = null;

            InputStream input = null;

            OutputStream output = null;

            try {

                //等待连接，连接成功后，返回一个Socket对象

                socket = serverSocket.accept();

                input = socket.getInputStream();

                output = socket.getOutputStream();

                // 创建Request对象并解析

                Request request = new Request(input);

                request.parse();

                // 检查是否是关闭服务命令

                if (request.getUri().equals(SHUTDOWN_COMMAND)) {

                    break;

                }

                // 创建 Response 对象

                Response response = new Response(output);

                response.setRequest(request);

                response.sendStaticResource();

                // 关闭 socket 对象

                socket.close();

            } catch (Exception e) {

                e.printStackTrace();

                continue;

            }

        }

    }

}

Request类：

package ex01.pyrmont;

import java.io.InputStream;

import java.io.IOException;

public class Request {

    private InputStream input;

    private String uri;

    public Request(InputStream input) {

        this.input = input;

    }

    //从InputStream中读取request信息，并从request中获取uri值

    public void parse() {

        StringBuffer request = new StringBuffer(2048);

        int i;

        byte[] buffer = new byte[2048];

        try {

            i = input.read(buffer);

        } catch (IOException e) {

            e.printStackTrace();

            i = -1;

        }

        for (int j = 0; j < i; j++) {

            request.append((char) buffer[j]);

        }

        System.out.print(request.toString());

        uri = parseUri(request.toString());

    }

    /**

     *

     * requestString形式如下：

     * GET /index.html HTTP/1.1

     * Host: localhost:8080

     * Connection: keep-alive

     * Cache-Control: max-age=0

     * ...

     * 该函数目的就是为了获取/index.html字符串

     */

    private String parseUri(String requestString) {

        int index1, index2;

        index1 = requestString.indexOf(' ');

        if (index1 != -1) {

            index2 = requestString.indexOf(' ', index1 + 1);

            if (index2 > index1)

                return requestString.substring(index1 + 1, index2);

        }

        return null;

    }

    public String getUri() {

        return uri;

    }

}

Response类：

package ex01.pyrmont;

import java.io.OutputStream;

import java.io.IOException;

import java.io.FileInputStream;

import java.io.File;

/*

  HTTP Response = Status-Line

    *(( general-header | response-header | entity-header ) CRLF)

    CRLF

    [ message-body ]

    Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF

*/

public class Response {

    private static final int BUFFER_SIZE = 1024;

    Request request;

    OutputStream output;

    public Response(OutputStream output) {

        this.output = output;

    }

    public void setRequest(Request request) {

        this.request = request;

    }

    public void sendStaticResource() throws IOException {

        byte[] bytes = new byte[BUFFER_SIZE];

        FileInputStream fis = null;

        try {

            //将web文件写入到OutputStream字节流中

            File file = new File(HttpServer.WEB_ROOT, request.getUri());

            if (file.exists()) {

                fis = new FileInputStream(file);

                int ch = fis.read(bytes, 0, BUFFER_SIZE);

                while (ch != -1) {

                    output.write(bytes, 0, ch);

                    ch = fis.read(bytes, 0, BUFFER_SIZE);

                }

            } else {

                // file not found

                String errorMessage = "HTTP/1.1 404 File Not Found\r\n" + "Content-Type: text/html\r\n"

                        + "Content-Length: 23\r\n" + "\r\n" + "<h1>File Not Found</h1>";

                output.write(errorMessage.getBytes());

            }

        } catch (Exception e) {

            // thrown if cannot instantiate a File object

            System.out.println(e.toString());

        } finally {

            if (fis != null)

                fis.close();

        }

    }

}