socketjava web服务器程序

2 月 Questions & Answers 240

我们的目标是开发一个web服务器，当通过web浏览器访问该服务器时，它将返回接收到的HTTP请求消息

我从虚拟机环境运行程序，并从本地机器访问服务器。下面是我的代码。当我在服务器运行时输入IP地址时，我只会得到一个空指针异常。任何指导都将不胜感激

import java.io.*;
import java.net.*;
import java.util.*;

public final class proj1 {

    public static void main(String[] args) throws Exception{
        int port = 9000;

        ServerSocket socket = new ServerSocket(port);

        while(true) {
            Socket connection = socket.accept();
            HttpRequest request = new HttpRequest(connection);
            Thread thread = new Thread(request);
            thread.start();
        }
    }

}

final class HttpRequest implements Runnable {
    //Declare Variables
    final static String CRLF = "\r\n";
    Socket socket;

    //Constructor
    public HttpRequest(Socket socket) throws Exception {
        this.socket = socket;
    }

    //Unimplemented Runnable Method
    @Override
    public void run() {
        try {
            processRequest();
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    private void processRequest() throws Exception {
        //Reference Socket Input and Output Streams
        InputStream is = socket.getInputStream();
        DataOutputStream os = null;

        //Input Stream Filters
        BufferedReader br = new BufferedReader(null);

        //Request Line of HTTP Request Message
        String requestLine = br.readLine();

        //Extract FileName From Request Line
        StringTokenizer tokens = new StringTokenizer(requestLine);
        tokens.nextToken();
        String fileName = tokens.nextToken();

        fileName = "." + fileName;

        //Open Requested File
        FileInputStream fis = null;
        boolean fileExists = true;

        try {
            fis = new FileInputStream(fileName);
        } catch (FileNotFoundException e) {
            fileExists = false;
        }

        //Debug
        System.out.println(requestLine);
        String headerLine = null;
        while ((headerLine = br.readLine()).length() != 0) {
            System.out.println(headerLine);
        }

        //Construct Response Message
        String statusLine = null;
        String contentTypeLine = null;
        String entityBody = null;

        if (fileExists) {
            statusLine = "statusLine";
            contentTypeLine = "Content-Type: " + contentType(fileName) + CRLF;
        } else {
            statusLine = "HTTP/1.0 404 Not Found" + CRLF;
            contentTypeLine = "Content-Type: text/html" + CRLF;
            entityBody = "<HTML>" + "<HEAD><TITLE>Not Found</TITLE></HEAD>" + "<BODY>Not Found</BODY></HTML>";
        }

        //Send Lines
        os.writeBytes(statusLine);
        os.writeBytes(contentTypeLine);
        os.writeBytes(CRLF);

        //Send Entity Body
        if (fileExists) {
            sendBytes(fis, os);
            fis.close();
        } else {
            os.writeBytes(entityBody);
        }

        //Close Streams and Sockets
        os.close();
        br.close();
        socket.close();
    }

    private static void sendBytes(FileInputStream fis, OutputStream os) throws Exception {
        byte[] buffer = new byte[1024];
        int bytes = 0;

        while ((bytes = fis.read(buffer)) != -1) {
            os.write(buffer, 0, bytes);
        }
    }

    private static String contentType(String fileName) {
        if (fileName.endsWith(".htm") || fileName.endsWith(".html")) {
            return "text/html";
        }

        return "application/octet-stream";
    }

}

Exception in thread "main" java.net.BindException: Address already in use: JVM_Bind
    at java.net.DualStackPlainSocketImpl.bind0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketBind(Unknown Source)
    at java.net.AbstractPlainSocketImpl.bind(Unknown Source)
    at java.net.PlainSocketImpl.bind(Unknown Source)
    at java.net.ServerSocket.bind(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at proj1.main(proj1.java:10)

这是我试图在eclipse中运行程序时的错误代码。。。当我在我的虚拟机上运行代码时，它运行正常，但每当我访问我机器上服务器的IP地址时，我在虚拟机上都不会收到响应消息和空指针异常

共 (1) 个答案

# 1 楼答案
new BufferedReader(null)将始终throw NullPointerException。你除了什么

顺便说一句，这总是个坏主意：
```
try {
    processRequest();
} catch (Exception e) {
    System.out.println(e);
}
```
如果不知道如何处理异常，至少重新抛出它以保留堆栈跟踪：
```
try {
    processRequest();
} catch (Exception e) {
    throw new RuntimeException(e);
}
```
这将引导您到达抛出异常的那一行

Python中文网

有 Java 编程相关的问题?

socketjava web服务器程序

共 (1) 个答案

# 1 楼答案