Android Multipart POST to Google App Engine not working
I'm developing an android program that shares data via POST with an App Engine program, all in java. When I POST using MultipartEntity the appengine program is unable to see any of my POST variables for some reason that I can't figure out!
Appengine Code:
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
resp.setContentType("text/plain");
resp.getWriter().println("Output:");
String mRoutine = req.getParameter("Routine");
resp.getWriter().println("Routine: " + mRoutine);
String mPMode = req.getParameter("PMode");
resp.getWriter().println("PMode: " + mPMode);
}
Working Android Snippet:
HttpPost post = new HttpPost("http://XXX.a开发者_StackOverflow中文版ppspot.com/Echo");
HttpClient client = new DefaultHttpClient();
post.setEntity(new UrlEncodedFormEntity(data,HTTP.UTF_8));
HttpResponse response = client.execute(post);
HttpEntity resmarkMessagesReadFrom = response.getEntity();
if (resmarkMessagesReadFrom != null) {
Result_STR= "Response:\n" + EntityUtils.toString(resmarkMessagesReadFrom);
mMSGBox.setText(Result_STR);
}
Failing Android Snippet:
HttpPost post = new HttpPost("http://XXX.appspot.com/Echo");
HttpClient client = new DefaultHttpClient();
MultipartEntity reqmarkMessagesReadFrom = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
try {
reqmarkMessagesReadFrom.addPart("Routine", new StringBody("Neutral"));
post.setEntity(reqmarkMessagesReadFrom);
HttpResponse response = client.execute(post);
HttpEntity resmarkMessagesReadFrom = response.getEntity();
if (resmarkMessagesReadFrom != null) {
Result_STR= "Response:\n" + EntityUtils.toString(resmarkMessagesReadFrom);
mMSGBox.setText(Result_STR);
}
Using the MultipartEntity
class on the client, you need to handle your doPost
in a different way server side, reading the files/parameters with an API like the Apache Commons FileUpload.
Google App Engine does not allow to write to filesystem, so you need to use the Streaming API.
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import java.io.InputStream;
..
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
try {
ServletFileUpload upload = new ServletFileUpload();
res.setContentType("text/plain");
FileItemIterator iterator = upload.getItemIterator(req);
while (iterator.hasNext()) {
String name = item.getFieldName();
FileItemStream item = iterator.next();
InputStream stream = item.openStream();
if (item.isFormField()) {
resp.getWriter().println((name + " : " + Streams.asString(stream));
}
}
} catch (Exception ex) {
throw new ServletException(ex);
}
}
Best answer I have found is one of google's own examples: http://code.google.com/intl/fr/appengine/kb/java.html#fileforms this uses FileUpload just like systempuntoout's example.
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import java.io.InputStream;
import java.io.IOException;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FileUpload extends HttpServlet {
private static final Logger log =
Logger.getLogger(FileUpload.class.getName());
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
try {
ServletFileUpload upload = new ServletFileUpload();
res.setContentType("text/plain");
FileItemIterator iterator = upload.getItemIterator(req);
while (iterator.hasNext()) {
FileItemStream item = iterator.next();
InputStream stream = item.openStream();
if (item.isFormField()) {
log.warning("Got a form field: " + item.getFieldName());
} else {
log.warning("Got an uploaded file: " + item.getFieldName() + ", name = " + item.getName());
// You now have the filename (item.getName() and the
// contents (which you can read from stream). Here we just
// print them back out to the servlet output stream, but you
// will probably want to do something more interesting (for
// example, wrap them in a Blob and commit them to the
// datastore).
int len;
byte[] buffer = new byte[8192];
while ((len = stream.read(buffer, 0, buffer.length)) != -1) {
res.getOutputStream().write(buffer, 0, len);
}
}
}
} catch (Exception ex) {
throw new ServletException(ex);
}
}
}
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