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Web入门-06.HTTP协议-协议解析

article 2025/1/25 9:03:22

浏览器发起HTTP协议请求，服务端通过ServerSocket接收并交给一个Socket对象（管道），然后解析浏览器的请求，并通过Socket管道向浏览器响应。

代码如下：

package com.gjw;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;

public class Server {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8080);
        System.out.println("server is running...");

        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("connected form" + socket.getRemoteSocketAddress());


            new Handler(socket).start();
        }
    }
}

class Handler extends Thread {
    private Socket socket;
    public Handler(Socket socket){
        this.socket = socket;
    }
    @Override
    public void run() {

        try (
                // 字节输入流：读入客户端发起的GET请求    字节输出流：写出服务端提供的服务
                InputStream is = socket.getInputStream();
                OutputStream os = socket.getOutputStream()
                )
        {
            handle(is, os);
        } catch (Exception e) {
            try {
                socket.close();
            } catch (IOException ex) {
                System.out.println("client disconnected");
            }
        }
    }

    private void handle(InputStream is, OutputStream os) throws Exception {
        // reader:读取客户端发来的GET请求
        BufferedReader reader = new BufferedReader(new InputStreamReader(is,StandardCharsets.UTF_8));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os,StandardCharsets.UTF_8));

        boolean requestOk = false;

        String first = reader.readLine();
        if (first.startsWith("GET / HTTP/1.")) {
            requestOk = true;
        }

        String header;
        while (!(header = reader.readLine()).isEmpty()) {    // 使用isEmpty判断，这样可以值判断到请求头就结束。因为请求头和请求体之间有空行
            System.out.println(header);
        }

/*        String line;
        while ((line = reader.readLine()) != null){
        不能使用 != null,因为HTTP请求中，请求头和请求体中是一个空行，使用请求!= null判断会使得无法将请求头和请求体分开，导致一直读到
        该http请求的末尾，这样的的话可能会导致该循环一直进行，因为客户端可能会不断发送HTTP请求，导致服务器无限等待输入特别是在客户端保持连接
        （例如HTTP/1.1中的Connection: keep-alive头部时）。这样，服务器可能不会及时处理和发送响应，从而导致后面的代码无法运行。
            System.out.println(line);
        }*/

        System.out.println(requestOk ? "Response OK" : "Response Error");

        if (requestOk) {
            InputStream input = Server.class.getClassLoader().getResourceAsStream("html/a.html");
            BufferedReader br = new BufferedReader(new InputStreamReader(input));
            StringBuffer sb = new StringBuffer();

            String content;
            while ((content = br.readLine()) != null) {
                sb.append(content);
            }


            br.close();
            int length = sb.toString().getBytes(StandardCharsets.UTF_8).length;

            writer.write("HTTP/1.1 200 OK\r\n");
            writer.write("Connection: keep-alive\r\n");
            writer.write("Content-Type: text/html\r\n");
            writer.write("Content-Length: " + length + "\r\n");
            writer.write("\r\n"); // 空行标识Header和Body的分隔
            writer.write(sb.toString());
            writer.flush();
        } else {
            writer.write("HTTP/1.0 404 Not Found\r\n");
            writer.write("Content-Length: 0\r\n");
            writer.write("\r\n");
            writer.flush();
        }
    }
}

响应的是一个表格数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        table {
            margin: 0 auto;
            text-align: center;
            border: 1px solid black;
            border-collapse: collapse;
            width: 500px;
        }
        th,td {
            border: 1px solid black;
        }
    </style>
</head>
<body>
    <table>
        <tr>
            <th>序号</th>
            <th>品牌名称</th>
            <th>企业名称</th>
        </tr>
        <tr>
            <td>010</td>
            <td>三只松鼠</td>
            <td>三只松鼠</td>
        </tr>
        <tr>
            <td>009</td>
            <td>优衣库</td>
            <td>优衣库</td>
        </tr>
        <tr>
            <td>008</td>
            <td>小米</td>
            <td>小米科技有限公司</td>
        </tr>
    </table>
</body>
</html>