【发布时间】：2014-07-11 00:28:48
【问题描述】：
我正在尝试使用 google app engine blobstore 上传文件。
它应该像这样工作：调用 BlobstoreService 来获取上传 url，提供回调 URL。客户端被重定向到上传 URL，发送数据，然后当他们完成后，他们将被重定向到回调 URL，并带有几个代表 blobstore 键的参数。
正如我们将看到的，开发服务器的行为与生产服务器不同。
在生产环境中，我的代码完成了上传，然后我没有重定向回我的回调 URL，而是收到 400 错误响应（暗示我的请求有问题）。如何在生产中调试它？我不知道如何打开 blobstore 的日志记录。
所以我尝试在本地针对开发服务器运行它。这一次，如果我不设置“内容长度”属性，我会得到 411（未设置内容长度）。但是，如果我尝试设置该属性，我会得到“IllegalStateException：已连接”。这些异常都不会发生在生产中。
所以我不知道下一步该去哪里。我需要让它对 dev 工作，希望我可以在本地调试 blobstore，或者找出它为什么不能在生产中的 blobstore 上工作。
public void upload(String uri, File file) throws IOException {
HttpURLConnection conn=null;
HttpURLConnection conn2=null;
FileInputStream fileInputStream = null;
DataOutputStream dos=null;
try {
String lineEnd = "\r\n";
String twoHyphens = "--";
String boundary = "*****";
int bytesRead, bytesAvailable, bufferSize;
byte[] buffer;
int maxBufferSize = 1 * 1024 * 1024;
// open a URL connection to the Servlet
fileInputStream = new FileInputStream(file);
URL url = new URL(uri);
// Open a HTTP connection to the URL
conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true); // Allow Inputs
conn.setDoOutput(true); // Allow Outputs
conn.setUseCaches(false); // Don't use a Cached Copy
conn.setInstanceFollowRedirects(false);
conn.setRequestMethod("POST");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("ENCTYPE", "multipart/form-data");
conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
// conn.setChunkedStreamingMode(1024);
conn.setRequestProperty("content-length", String.valueOf(file.length())); //caused IllegalStateException "Already connected" locally, but not remotely
log("Orignal URL: " + conn.getURL());
//conn.connect(); //TODO duplicates url.openConnection() above?
conn.getInputStream(); //so we can follow the redirect
String redirectedUrl = conn.getHeaderField("Location");
log("Redirected URL: " + redirectedUrl);
//this is horrible and messy but let's get it working then clean it up later
conn.disconnect();
url = new URL(redirectedUrl);
// Open a new HTTP connection to the URL
conn2 = (HttpURLConnection) url.openConnection();
conn2.setDoInput(true); // Allow Inputs
conn2.setDoOutput(true); // Allow Outputs
conn2.setUseCaches(false); // Don't use a Cached Copy
conn2.setInstanceFollowRedirects(false);
conn2.setRequestMethod("POST");
conn2.setRequestProperty("Connection", "Keep-Alive");
conn2.setRequestProperty("ENCTYPE", "multipart/form-data");
conn2.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
conn2.setChunkedStreamingMode(maxBufferSize);
conn2.setRequestProperty("Content-Length", String.valueOf(file.length()));
conn2.connect();
dos = new DataOutputStream(conn2.getOutputStream());
dos.writeBytes(twoHyphens + boundary + lineEnd);
dos.writeBytes("Content-Disposition: form-data; name=\"myFile\";filename=\""+file.getName()+"\"" + lineEnd);
dos.writeBytes(lineEnd);
// create a buffer of maximum size
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
buffer = new byte[bufferSize];
// read file and write it into form...
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
while (bytesRead > 0) {
dos.write(buffer, 0, bufferSize);
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
}
// send multipart form data necesssary after file data...
dos.writeBytes(lineEnd);
dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
// Responses from the server (code and message)
int serverResponseCode = conn2.getResponseCode();
String serverResponseMessage = conn2.getResponseMessage();
//we are expecting another redirect here
log("aaaargh! 400 instead of 302! "+serverResponseCode+" to "+conn2.getHeaderField("Location"));
}catch (IOException e) {
log(e.getMessage());
throw e;
}catch(Exception e) {
log(e.getMessage());
throw new IOException(e);
} finally {
//close the streams //
if (dos!=null) {
try {
dos.flush();
dos.close();
}catch(IOException ioe){}
}
if (fileInputStream!=null)
try {
fileInputStream.close();
}catch(IOException ioe){}
if (conn!=null )
try {
conn.disconnect();
}catch(Exception ioe){}
if (conn2!=null)
try {
conn2.disconnect();
}catch(Exception ioe){}
}
}
注意，上面的 serverResponseMessage 字符串作为“错误请求”从生产 blobstore 返回
【问题讨论】：
-
正如您所说：您向客户端提供一个上传 URL，然后收到一个简单的回调。这段代码是干什么用的？
-
我正在尝试使用 google 应用引擎 blobstore 从 android 客户端上传文件。
-
我怀疑您实际上没有处理后端 servlet 或控制器的确切名称-值对参数。因此，您遇到了这个问题。还要检查您的文件是否已上传到 blobstore。
标签： java google-app-engine http servlets io