用java举一个web服务器实现功能的例子

以下是使用Java实现一个简单的Web服务器的示例代码：

import java.io.*;
import java.net.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Date;

public class SimpleWebServer {
    public static void main(String[] args) throws IOException {
        int port = 8080;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("Server is listening on port " + port);

        while (true) {
            Socket clientSocket = serverSocket.accept();
            System.out.println("Client connected from " + clientSocket.getInetAddress().getHostAddress());

            InputStream inputStream = clientSocket.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            String request = reader.readLine();
            System.out.println("Request: " + request);

            String[] tokens = request.split(" ");
            String method = tokens[0];
            String path = tokens[1];

            if (method.equals("GET")) {
                Path filePath = Paths.get("." + path);
                if (Files.exists(filePath) && !Files.isDirectory(filePath)) {
                    byte[] fileContent = Files.readAllBytes(filePath);
                    OutputStream outputStream = clientSocket.getOutputStream();
                    outputStream.write("HTTP/1.1 200 OK\r\n".getBytes());
                    outputStream.write(("Content-Type: " + Files.probeContentType(filePath) + "\r\n").getBytes());
                    outputStream.write(("Content-Length: " + fileContent.length + "\r\n").getBytes());
                    outputStream.write(("Date: " + new Date() + "\r\n").getBytes());
                    outputStream.write("\r\n".getBytes());
                    outputStream.write(fileContent);
                    outputStream.flush();
                } else {
                    OutputStream outputStream = clientSocket.getOutputStream();
                    outputStream.write("HTTP/1.1 404 Not Found\r\n".getBytes());
                    outputStream.write(("Date: " + new Date() + "\r\n").getBytes());
                    outputStream.write("\r\n".getBytes());
                    outputStream.flush();
                }
            }

            clientSocket.close();
            System.out.println("Client disconnected");
        }
    }
}

这个简单的Web服务器监听8080端口，当接收到客户端的请求后，根据请求路径读取相应的文件并返回给客户端。如果文件不存在，则返回404错误。这个示例仅仅是一个初步的实现，还需要进行优化和改进，例如处理POST请求、支持多线程等。