手动实现Tomcat底层机制+自己设计Servlet

实现一个简化版的Tomcat来自定义Servlet处理请求，需要实现一个HTTP服务器，这个服务器能够理解HTTP请求并能够响应。以下是一个非常简化的实现，仅包含实现核心逻辑的代码片段。

import java.io.*;
import java.net.*;
import java.util.*;
 
public class SimpleTomcat {
 
    private int port = 8080;
    private ServerSocket serverSocket;
    private final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
 
    public SimpleTomcat() throws IOException {
        serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
    }
 
    public void start() throws IOException {
        Socket socket = null;
        InputStream input = null;
        OutputStream output = null;
        PrintWriter writer = null;
 
        System.out.println("Server is running on port " + port);
 
        while (true) {
            try {
                socket = serverSocket.accept();
                input = socket.getInputStream();
                output = socket.getOutputStream();
 
                // 创建writer将内容写入到输出流
                writer = new PrintWriter(new OutputStreamWriter(output));
 
                // 解析请求
                Parser parser = new Parser(input);
                String requestLine = parser.parseRequestLine();
                System.out.println("Request line: " + requestLine);
 
                // 创建请求对象
                HttpRequest request = new HttpRequest(requestLine);
 
                // 处理请求
                handleRequest(request, writer);
 
                // 关闭writer, socket等资源
                writer.close();
                socket.close();
 
            } catch (Exception e) {
                e.printStackTrace();
                continue;
            }
        }
    }
 
    private void handleRequest(HttpRequest request, PrintWriter writer) {
        String uri = request.getUri();
        File file = new File(WEB_ROOT, uri);
 
        try {
            if (file.exists()) {
                String contentType = getMimeType(file);
                String statusLine = "HTTP/1.1 200 OK";
                writer.println(statusLine);
                writer.println("Content-Type: " + contentType);
                writer.println();
 
                // 发送文件内容
                Files.copy(file.toPath(), writer.getOutputStream());
            } else {
                String statusLine = "HTTP/1.1 404 Not Found";
                writer.println(statusLine);
                writer.println("Content-Type: text/html");