Question

我想将文件从blobstore上传到名为Wisita的服务。以下是上传API的文档：

到目前为止，这是我的代码（我想我可能会错过ssl选项）

FileService fileService = FileServiceFactory.getFileService();
AppEngineFile binaryFile = fileService.getBlobFile(new BlobKey("my blob key"));

String param = "api_password=" + URLEncoder.encode("my wisita key", "UTF-8") +
                "&project_id=" + URLEncoder.encode("folder_id", "UTF-8");
String charset = "UTF-8";

String boundary = Long.toHexString(System.currentTimeMillis()); // Just generate some unique random value.
String CRLF = "\r\n"; // Line separator required by multipart/form-data.

URLConnection connection = new URL("https://upload.wistia.com/").openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
PrintWriter writer = null;
try {
    OutputStream output = connection.getOutputStream();
    writer = new PrintWriter(new OutputStreamWriter(output, charset), true); // true = autoFlush, important!

    // Send normal param.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF);
    writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);
    writer.append(CRLF);
    writer.append(param).append(CRLF).flush();

    // Send binary file.
    writer.append("--" + boundary).append(CRLF);
    writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + binaryFile.getNamePart() + "\"").append(CRLF);
    writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(binaryFile.getNamePart())).append(CRLF);
    writer.append("Content-Transfer-Encoding: binary").append(CRLF);
    writer.append(CRLF).flush();
    InputStream input = null;
    try {
            FileReadChannel ch = fileService.openReadChannel(binaryFile, true);
            input = Channels.newInputStream(ch);
            byte[] buffer = new byte[1024];
            for (int length = 0; (length = input.read(buffer)) > 0;) {
                output.write(buffer, 0, length);
            }
            output.flush(); // Important! Output cannot be closed. Close of writer will close output as well.
    } finally {
            if (input != null) try { input.close(); } catch (IOException logOrIgnore) {}
            }
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of binary boundary.

    // End of multipart/form-data.
    writer.append("--" + boundary + "--").append(CRLF);

    //resp part
    InputStream responseStream = new BufferedInputStream(connection.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();
    resp.getWriter().write(response);

    } finally {
        if (writer != null) writer.close();
    }

此代码出现了500错误

Answer 1

感谢您的提问。作为参考，它解决了我正在做类似任务的问题。

我对代码所做的第一个更改是将doOutput和doInput都设置为true（而不仅仅是doOutput）。我不确定这是否有所不同，因为我认为这是默认的。

con.setDoOutput(true);
con.setDoInput(true);

您确定您的内容编码正确吗？我使用了相同的设置和配置，但我没有使用PrintWriter，而只是调用write并从我的String中传递字节，从文件内容传递字节：

connection.getOutputStream().write("Content-Disposition blah...".getBytes());
connection.getOutputStream().write(fileContentsByteArray);
connection.flush();

然后，我通过读取连接的输入流，从我的Web服务中读取所需的数据，如下所示：

FileOutputStream out = new FileOutputStream("received.bin");
InputStream in = connection.getInputStream();
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
    out.write(buffer, 0, len);
}
out.close();

Answer 2

如何更改传递正常参数？

在：

param=..api_password...project_id...;
// Send normal param.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF);
writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);
writer.append(CRLF);
writer.append(param).append(CRLF).flush();

后：

// Send normal param.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"api_password\"").append(CRLF);
writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);
writer.append(CRLF);
writer.append(api_password).append(CRLF).flush();
// Send normal param.
writer.append("--" + boundary).append(CRLF);
writer.append("Content-Disposition: form-data; name=\"project_id\"").append(CRLF);
writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF);
writer.append(CRLF);
writer.append(project_id).append(CRLF).flush();

GAE使用SSL发送带有multipart / form-data的文件，来自blobstore的文件

2 个答案: