如何仅使用标准网络库发送HTTP响应？ [英] How can I send an HTTP Response using only standard network libraries?

问题描述

我正在开发一个Web编程类的第一个家庭作业项目，即用Java编写一个简单的Web服务器。我正处于数据来回传输的地步，对于未经训练的眼睛，我的婴儿服务器似乎工作正常。但是，我找不到发送适当回复的方法。 （换句话说，无效页面请求将显示404-ish HTML页面，但在查看响应标头时仍会返回200 OK状态）。

I'm working on my first homework project in a web programming class, which is to write a simple web server in Java. I'm at the point where I have data being transmitted back and forth, and to the untrained eye, my baby server seems to be working fine. However, I can't find a way to send appropriate responses. (In other words, an invalid page request would show a 404-ish HTML page, but it still returns a 200 OK status when I view response headers).

我只能使用标准网络库进行套接字管理，而标准I / O库则可以从输入流中读取和写入字节和字符串。以下是一些相关的代码：

I'm limited to being able to use standard network libraries for socket management and standard I/O libraries to read and write bytes and strings from an input stream. Here's some pertinent code:

来自我的主...

            ServerSocket servSocket = new ServerSocket(port, 10);           // Bind the socket to the port
        System.out.println("Opened port " + port + " successfully!");

                while(true) {
            //Accept the incoming socket, which means that the server process will
            //wait until the client connects, then prepare to handle client commands
            Socket newDataSocket = servSocket.accept();
            System.out.println("Client socket created and connected to server socket...");

            handleClient(newDataSocket);                                //Call handleClient method
        }   

来自handleClient方法...（在循环内解析请求方法和路径）

From the handleClient method...(inside a loop that parses the request method and path)

                    if(checkURL.compareTo("/status") == 0)  {   // Check to see if status page has been requested
                    System.out.println("STATUS PAGE");      // TEMPORARY. JUST TO MAKE SURE WE ARE PROPERLY ACCESSING STATUS PAGE
                    sendFile("/status.html", dataStream);
                }
                else {
                    sendFile(checkURL, dataStream);         // If not status, just try the input as a file name
                }

来自sendFile方法...

From sendFile method...

        File f = new File(where);                                               // Create the file object
    if(f.exists() == true) {                                                        // Test if the file even exists so we can handle a 404 if not.
        DataInputStream din;
        try {
            din = new DataInputStream(new FileInputStream(f));
            int len = (int) f.length();                                     // Gets length of file in bytes
            byte[] buf = new byte[len];
            din.readFully(buf);
            writer.write("HTTP/1.1 200 OK\r\n");                            // Return status code for OK (200)
            writer.write("Content-Length: " + len + "\r\n");                // WAS WRITING TO THE WRONG STREAM BEFORE!
            writer.write("Content-Type: "+type+"\r\n\r\n\r\n");             // TODO VERIFY NEW CONTENT-TYPE CODE
            out.write(buf);                                                 // Writes the FILE contents to the client
            out.flush();
            out.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();                                            // Not really handled since that's not part of project spec, strictly for debug.
        }
    }
    else {
        writer.write("HTTP/1.1 404 Not Found\r\n");                         // Attempting to handle 404 as simple as possible.
        writer.write("Content-Type: text/html\r\n\r\n\r\n");
        sendFile("/404.html", sock);
    }

任何人都能解释一下，在sendFile的条件下，我可以改变响应在404块中（就像我之前说过的，响应头仍然显示200 OK）？这是我的废话，我只是想使用HTTPResponse类，但我不能。 （另外，如果f.exists == true，则不显示内容长度和类型。）

Can anybody explain how, in the conditional from sendFile, I can change the response in the 404 block (Like I said before, the response headers still show 200 OK)? This is bugging the crap out of me, and I just want to use the HTTPResponse class but I can't. (Also, content length and type aren't displayed if f.exists == true.)

谢谢！

推荐答案

您看到的问题很可能与您的编写器上缺少 flush（）有关/ code>。根据您使用哪种类型的 Writer ，首先将字节写入需要刷新到流的缓冲区。这可以解释为什么输出中缺少 Content-Length 和 Content-Type 。只需在将其他数据写入流之前将其刷新。

The problem you are seeing is most likely related to a missing flush() on your writer. Depending on which type of Writer you use the bytes are first written to a buffer that needs to be flushed to the stream. This would explain why Content-Length and Content-Type are missing in the output. Just flush it before you write additional data to the stream.

进一步调用 sendFile（/ 404.html，sock）; 。你没有在这里发布完整的方法 - 但我想你在 sendFile 内递归调用它，因此发送 200 OK 文件状态 /404.html 。

Further you call sendFile("/404.html", sock);. You did not post the full method here - but I suppose that you call it recursively inside sendFile and thus send the 200 OK status for your file /404.html.

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