如何处理从Java客户端上传服务器端HTTP文件

Question

I want to upload a file from a client to a server.

Client: Java using HTTP post Server: Java Servlet

I have added the client side coding here. But, i don't have any idea with the server side processing. Please do help me with a code snippet.

 private String Tag = "UPLOADER";
    private String urlString = "http://192.168.42.140:8080/sampweb";
    HttpURLConnection conn;
    String exsistingFileName = "/sdcard/log.txt";
    String lineEnd = "\r\n";
    String twoHyphens = "--";
    String boundary = "*****";
    try {
        // ------------------ CLIENT REQUEST

        Log.e(Tag, "Inside second Method");

        FileInputStream fileInputStream = new FileInputStream(new File(
                exsistingFileName));

        // open a URL connection to the Servlet

        URL url = new URL(urlString);

        // Open a HTTP connection to the URL

        conn = (HttpURLConnection) url.openConnection();

        // Allow Inputs
        conn.setDoInput(true);

        // Allow Outputs
        conn.setDoOutput(true);

        // Don't use a cached copy.
        conn.setUseCaches(false);

        // Use a post method.
        conn.setRequestMethod("POST");

        conn.setRequestProperty("Connection", "Keep-Alive");

        conn.setRequestProperty("Content-Type",
                "multipart/form-data;boundary=" + boundary);

        DataOutputStream dos = new DataOutputStream(conn.getOutputStream());

        dos.writeBytes(twoHyphens + boundary + lineEnd);
        dos
                .writeBytes("Content-Disposition: post-data; name=uploadedfile;filename="
                        + exsistingFileName + "" + lineEnd);
        dos.writeBytes(lineEnd);

        Log.e(Tag, "Headers are written");

        // create a buffer of maximum size

        int bytesAvailable = fileInputStream.available();
        int maxBufferSize = 1000;
        // int bufferSize = Math.min(bytesAvailable, maxBufferSize);
        byte[] buffer = new byte[bytesAvailable];

        // read file and write it into form...

        int bytesRead = fileInputStream.read(buffer, 0, bytesAvailable);

        while (bytesRead > 0) {
            dos.write(buffer, 0, bytesAvailable);
            bytesAvailable = fileInputStream.available();
            bytesAvailable = Math.min(bytesAvailable, maxBufferSize);
            bytesRead = fileInputStream.read(buffer, 0, bytesAvailable);
        }

        // send multipart form data necessary after file data...

        dos.writeBytes(lineEnd);
        dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

        // close streams
        Log.e(Tag, "File is written");
        fileInputStream.close();
        dos.flush();
        dos.close();

    } catch (MalformedURLException ex) {
        Log.e(Tag, "error: " + ex.getMessage(), ex);
    }

    catch (IOException ioe) {
        Log.e(Tag, "error: " + ioe.getMessage(), ioe);
    }

    try {
        BufferedReader rd = new BufferedReader(new InputStreamReader(conn
                .getInputStream()));
        String line;
        while ((line = rd.readLine()) != null) {
            Log.e("Dialoge Box", "Message: " + line);
        }
        rd.close();

    } catch (IOException ioex) {
        Log.e("MediaPlayer", "error: " + ioex.getMessage(), ioex);
    }
}

I'm new to the server programming. If i have done any mistakes do clarify me. Thanks!

Answer 1

The best library to achieve this is still the Apache Commons File Upload . It is well documented and easy to use. If you ran into any issues, please check FAQ first.