Question

（这是针对已签名的小程序，我决定不使用HTTPClient来保持我的jar非常小）

我正在使用HttpURLConnection将文件从用户成功上传到使用多部分表单帖子的服务器。

问题在于HttpURLConnection正在缓存数据 - 在发送之前。因此，当我从文件中读取并写入Outputstream时，它只是缓冲数据 - 因此我的进度条显示上传状态是完全错误的。请注意，表单邮政编码是有效的，文件确实上传正确，返回代码为200.

那么如何确保HttpURLConnection不会缓存我发送给服务器的数据呢？

这是我的来源：

public UploadResponse send(String formPostUrlStr,String fileFieldName,File targetFile, Map<String, String> valuesMap, UploadStatusListener uploadStatusListener) throws Exception{


    String sendStr=getBoundaryMessage(Boundary,  valuesMap, fileFieldName, targetFile.getName(), valuesMap.get("content-type") );//"image/png") ;

    System.out.println(" multi-part start \n "+ sendStr+ " multi-part end \n");

    String lenstr=Long.toString((long)(sendStr.length()*2)+ targetFile.length());
    System.out.println("Content-Length"+ lenstr);
                        //Content-Length

    URL url= new URL(formPostUrlStr);
    long startTime= System.currentTimeMillis();
    HttpURLConnection s3Connection = (HttpURLConnection) url.openConnection();

    System.out.println("opened url to "+ formPostUrlStr +", connection ok ..");
    s3Connection.setRequestProperty("Content-Type", "multipart/form-data; boundary="
            + Boundary);
    s3Connection.setRequestProperty("content-length",  lenstr);




    s3Connection.setDoOutput(true);
    s3Connection.setDoInput(true);
    s3Connection.setUseCaches(false);
     s3Connection.setInstanceFollowRedirects(true);
    s3Connection.setAllowUserInteraction(true);
    s3Connection.setRequestProperty("User-Agent", "Mozilla/4.5");


    if (uploadStatusListener != null) {
        uploadStatusListener.statusUpdate(targetFile.length(), 0);
    }


    String debugStr= s3Connection.toString();
    System.out.println("conmnection "+ debugStr);


    DataOutputStream httpOut = new DataOutputStream(s3Connection.getOutputStream());

    System.out.println("opened DataOutputStream ok ..");




    httpOut.write(sendStr.getBytes());


    //httpOut.flush();

  System.out.println("httpOut.flush 1 ok ..");
    FileInputStream uploadFileReader = new FileInputStream(targetFile);
    long totalBytes = uploadFileReader.available();
    if (uploadStatusListener != null) {
        uploadStatusListener.statusUpdate(totalBytes, 0);
    }
    System.out.println(" uploading file with size  "+ uploadFileReader.available());
    int bufSize = 102400;
    long availableBytesToRead;
    long totalSent = 0;
    while ((availableBytesToRead = uploadFileReader.available()) > 0) {
        byte[] bufferBytesRead;
        bufferBytesRead = availableBytesToRead >= bufSize ? new byte[bufSize]
                : new byte[(int)availableBytesToRead];
        int count = uploadFileReader.read(bufferBytesRead);
        try{
            httpOut.write(bufferBytesRead);
            totalSent += ((long) count);
            System.out.println(" wrote bytes = "+count+ ", total sent = "+ totalSent +", pendingSize"+ (availableBytesToRead-count) );
        }
        catch(IOException ioe){
            System.out.println(" io exceotion e"+ ioe.getMessage());
            throw ioe;
        }

        //httpOut.flush();
        if (uploadStatusListener != null) {
            uploadStatusListener.statusUpdate(totalBytes, totalSent);
        }

    }
    // FILE DATA END 
    httpOut.write(("--" + Boundary + "--\r\n").getBytes());



    // form end     
    httpOut.write(("--" + Boundary + "--\r\n").getBytes());

    httpOut.flush();
    httpOut.close();

    long endTime= System.currentTimeMillis();

    System.out.println("Completed Writing Data to S3 Connection in "+ (endTime-startTime)+"ms.,now waiting for rsponse code ");
    int code=s3Connection.getResponseCode();
    long endTime2= System.currentTimeMillis();
    System.out.println("Completed Sendind Data to S3 in "+ (endTime2-startTime)+ "ms., rsponse code time "+ (endTime2-endTime)+"ms. ");


    UploadResponse uploadResponse = new UploadResponse();

    uploadResponse.setCode(code);

    System.out.println(" response code : " + code);

    StringBuilder response = new StringBuilder();
    byte[] respBuffer = new byte[4096];


    if (code > 300) {
        if (code == 404) {
            throw new Exception("Error 404");
        }
        BufferedReader err = new BufferedReader(
                new InputStreamReader(s3Connection.getErrorStream()));
        String ret;
        StringBuffer buff = new StringBuffer();
        while ((ret = err.readLine()) != null) {
            buff.append(ret);
        }
        uploadResponse.setMessage(buff.toString());
        System.out.println(" error :"+ buff.toString());
        err.close();


    } else {
        BufferedReader inp = new BufferedReader(
                new InputStreamReader(s3Connection.getInputStream()));
        StringBuffer buff = new StringBuffer();
        String ret;
        while ((ret = inp.readLine()) != null) {
            buff.append(ret);
        }
        inp.close();
        uploadResponse.setMessage(buff.toString());
        if(buff.toString().contains("fail"))
            throw new Exception("Upload failed");
    }        

    System.out.println(response.toString());

    return uploadResponse;        

}

}

Answer 1

我有同样的问题。我没有找到任何其他解决方案，而不是在原始套接字上写我的HTTP请求。你找到了更好的解决方法吗？

编辑：我刚才：我们只需要在从url.openConnection（）获取的HttpURLConnection对象上使用obj.setFixedLengthStreamingMode（12345），其中12345是POST请求体的长度。

Answer 2

作为@Antares给出的答案的补充，当您事先不知道内容大小时，可以使用另一种方法setChunkedStreamingMode。因此，当您执行POST请求时，请在连接上调用该方法：

HttpURLConnection connection = ...
connection.setRequestMethod("POST");
connection.setDoOutput(true);
connection.setChunkedStreamingMode(0);
connection.connect();
... connection.getOutputStream();

这将避免OutputStream在开始发送之前缓冲整个内容。

如何在Java HttpURLConnection中为多部分表单发布禁用缓冲？

2 个答案: