使用POST和HttpURLConnection发送文件

Question

由于Android开发人员建议使用HttpURLConnection类，我想知道是否有人能为我提供一个很好的例子，说明如何通过POST将位图“文件”（实际上是内存流）发送到Apache HTTP服务器。我对cookie、身份验证或任何复杂的东西都不感兴趣，但我只想有一个可靠的逻辑实现。我在这里看到的所有例子看起来更像是“让我们试试这个，也许它会奏效”。

现在，我有以下代码：

URL url;
HttpURLConnection urlConnection = null;
try {
    url = new URL("http://example.com/server.cgi");

    urlConnection = (HttpURLConnection) url.openConnection();

} catch (Exception e) {
    this.showDialog(getApplicationContext(), e.getMessage());
}
finally {
    if (urlConnection != null)
    {
        urlConnection.disconnect();
    }
}

其中showDialog应该只显示一个警报对话框（如果URL无效？）。

现在，让我们假设我这样生成一个位图：位图图像=this.get位图（）在一个从View派生的控件中，我想通过POST发送它。实现这样的事情的正确过程是什么？我需要使用什么类？我可以像在这个例子中一样使用HttpPost吗？如果是这样，我将如何为我的位图构造InputStreamEntity？我会发现要求首先将位图存储在设备上的文件中是令人反感的。

我还应该提到，我真的需要将原始位图的每一个未更改的像素发送到服务器，所以我无法将其转换为JPEG。

Answer 1

使用多功能以简单的方式在服务器上上传带有某些参数的文件。

多功能性。JAVA

public class MultipartUtility {

    private final String boundary;
    private static final String LINE_FEED = "\r\n";
    private HttpURLConnection httpConn;
    private String charset;
    private OutputStream outputStream;
    private PrintWriter writer;

    /**
     * This constructor initializes a new HTTP POST request with content type
     * is set to multipart/form-data
     *
     * @param requestURL
     * @param charset
     * @throws IOException
     */
    public MultipartUtility(String requestURL, String charset)
            throws IOException {
        this.charset = charset;

        // creates a unique boundary based on time stamp
        boundary = "===" + System.currentTimeMillis() + "===";

        URL url = new URL(requestURL);
        Log.e("URL", "URL : " + requestURL.toString());
        httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setUseCaches(false);
        httpConn.setDoOutput(true); // indicates POST method
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("Content-Type",
                "multipart/form-data; boundary=" + boundary);
        httpConn.setRequestProperty("User-Agent", "CodeJava Agent");
        httpConn.setRequestProperty("Test", "Bonjour");
        outputStream = httpConn.getOutputStream();
        writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
                true);
    }

    /**
     * Adds a form field to the request
     *
     * @param name  field name
     * @param value field value
     */
    public void addFormField(String name, String value) {
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append("Content-Disposition: form-data; name=\"" + name + "\"")
                .append(LINE_FEED);
        writer.append("Content-Type: text/plain; charset=" + charset).append(
                LINE_FEED);
        writer.append(LINE_FEED);
        writer.append(value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a upload file section to the request
     *
     * @param fieldName  name attribute in <input type="file" name="..." />
     * @param uploadFile a File to be uploaded
     * @throws IOException
     */
    public void addFilePart(String fieldName, File uploadFile)
            throws IOException {
        String fileName = uploadFile.getName();
        writer.append("--" + boundary).append(LINE_FEED);
        writer.append(
                "Content-Disposition: form-data; name=\"" + fieldName
                        + "\"; filename=\"" + fileName + "\"")
                .append(LINE_FEED);
        writer.append(
                "Content-Type: "
                        + URLConnection.guessContentTypeFromName(fileName))
                .append(LINE_FEED);
        writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
        writer.append(LINE_FEED);
        writer.flush();

        FileInputStream inputStream = new FileInputStream(uploadFile);
        byte[] buffer = new byte[4096];
        int bytesRead = -1;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
        }
        outputStream.flush();
        inputStream.close();

        writer.append(LINE_FEED);
        writer.flush();
    }

    /**
     * Adds a header field to the request.
     *
     * @param name  - name of the header field
     * @param value - value of the header field
     */
    public void addHeaderField(String name, String value) {
        writer.append(name + ": " + value).append(LINE_FEED);
        writer.flush();
    }

    /**
     * Completes the request and receives response from the server.
     *
     * @return a list of Strings as response in case the server returned
     * status OK, otherwise an exception is thrown.
     * @throws IOException
     */
    public String finish() throws IOException {
        StringBuffer response = new StringBuffer();

        writer.append(LINE_FEED).flush();
        writer.append("--" + boundary + "--").append(LINE_FEED);
        writer.close();

        // checks server's status code first
        int status = httpConn.getResponseCode();
        if (status == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    httpConn.getInputStream()));
            String line = null;
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
            reader.close();
            httpConn.disconnect();
        } else {
            throw new IOException("Server returned non-OK status: " + status);
        }

        return response.toString();
    }
}

要上传您可以文件以及参数。

注意：将下面的代码放在非ui线程中以获得响应。

String charset = "UTF-8";
String requestURL = "YOUR_URL";

MultipartUtility multipart = new MultipartUtility(requestURL, charset);
multipart.addFormField("param_name_1", "param_value");
multipart.addFormField("param_name_2", "param_value");
multipart.addFormField("param_name_3", "param_value");
multipart.addFilePart("file_param_1", new File(file_path));
String response = multipart.finish(); // response from server.

Answer 2

我实际上找到了一个更好的方法来发送文件使用HttpURLConnection使用MultipartEntity

private static String multipost(String urlString, MultipartEntity reqEntity) {
    try {
        URL url = new URL(urlString);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(10000);
        conn.setConnectTimeout(15000);
        conn.setRequestMethod("POST");
        conn.setUseCaches(false);
        conn.setDoInput(true);
        conn.setDoOutput(true);

        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.addRequestProperty("Content-length", reqEntity.getContentLength()+"");
        conn.addRequestProperty(reqEntity.getContentType().getName(), reqEntity.getContentType().getValue());

        OutputStream os = conn.getOutputStream();
        reqEntity.writeTo(conn.getOutputStream());
        os.close();
        conn.connect();

        if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
            return readStream(conn.getInputStream());
        }

    } catch (Exception e) {
        Log.e(TAG, "multipart post error " + e + "(" + urlString + ")");
    }
    return null;        
}

private static String readStream(InputStream in) {
    BufferedReader reader = null;
    StringBuilder builder = new StringBuilder();
    try {
        reader = new BufferedReader(new InputStreamReader(in));
        String line = "";
        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return builder.toString();
} 

假设您正在上传包含位图数据的图像：

    Bitmap bitmap = ...;
    String filename = "filename.png";
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, bos);
    ContentBody contentPart = new ByteArrayBody(bos.toByteArray(), filename);

    MultipartEntity reqEntity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
    reqEntity.addPart("picture", contentPart);
    String response = multipost("http://server.com", reqEntity);

瞧！您的帖子数据将包含图片字段以及服务器上的文件名和路径。

Answer 3

我不知道为什么HttpURLConnection类不提供任何方法来发送文件，而不必手动编写文件包装器。以下是我最后做的事情，但如果有人知道更好的解决方案，请告诉我。

输入数据：

Bitmap bitmap = myView.getBitmap();

静态素材：

String attachmentName = "bitmap";
String attachmentFileName = "bitmap.bmp";
String crlf = "\r\n";
String twoHyphens = "--";
String boundary =  "*****";

设置请求：

HttpURLConnection httpUrlConnection = null;
URL url = new URL("http://example.com/server.cgi");
httpUrlConnection = (HttpURLConnection) url.openConnection();
httpUrlConnection.setUseCaches(false);
httpUrlConnection.setDoOutput(true);

httpUrlConnection.setRequestMethod("POST");
httpUrlConnection.setRequestProperty("Connection", "Keep-Alive");
httpUrlConnection.setRequestProperty("Cache-Control", "no-cache");
httpUrlConnection.setRequestProperty(
    "Content-Type", "multipart/form-data;boundary=" + this.boundary);

启动内容包装：

DataOutputStream request = new DataOutputStream(
    httpUrlConnection.getOutputStream());

request.writeBytes(this.twoHyphens + this.boundary + this.crlf);
request.writeBytes("Content-Disposition: form-data; name=\"" +
    this.attachmentName + "\";filename=\"" + 
    this.attachmentFileName + "\"" + this.crlf);
request.writeBytes(this.crlf);

将位图转换为字节缓冲：

//I want to send only 8 bit black & white bitmaps
byte[] pixels = new byte[bitmap.getWidth() * bitmap.getHeight()];
for (int i = 0; i < bitmap.getWidth(); ++i) {
    for (int j = 0; j < bitmap.getHeight(); ++j) {
        //we're interested only in the MSB of the first byte, 
        //since the other 3 bytes are identical for B&W images
        pixels[i + j] = (byte) ((bitmap.getPixel(i, j) & 0x80) >> 7);
    }
}

request.write(pixels);

结束内容包装器：

request.writeBytes(this.crlf);
request.writeBytes(this.twoHyphens + this.boundary + 
    this.twoHyphens + this.crlf);

刷新输出缓冲区：

request.flush();
request.close();

获得回复：

InputStream responseStream = new 
    BufferedInputStream(httpUrlConnection.getInputStream());

BufferedReader responseStreamReader = 
    new BufferedReader(new InputStreamReader(responseStream));

String line = "";
StringBuilder stringBuilder = new StringBuilder();

while ((line = responseStreamReader.readLine()) != null) {
    stringBuilder.append(line).append("\n");
}
responseStreamReader.close();

String response = stringBuilder.toString();

关闭响应流：

responseStream.close();

关闭连接：

httpUrlConnection.disconnect();

PS：当然，我必须将请求包装在私有类AsyncUploadBitmaps extends AsyncTask中