Google appengine blobstore upload handler processing extra form post parameters - google-app-engine

Question

I wish to have a file upload form that in addition to the file selection input , also has other input fields like textarea, dropdown etc. The problem is that I cannot access any post parameters other than the file in my blobstore upload handler. I am using the following function call to get the parameter name but it always returns an empty screen.
par = self.request.get("par")
I found another question with a similar problem Uploading a video to google app engine blobstore. The answer to that question suggests a workaround solution to set the filename to the parameter you wish to read which is not sufficient for my needs. Is there a way to access other form parameters in the post method of blobstore upload handler?

Answer 1

Did you find the solution?
In my experience, when using form/multipart request doesn't include the other parameters and they have to be dug out manually.
This is how I dig out parameters out of request that is used to send a file.
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import javax.servlet.http.HttpServletRequest;
// for reading form data when posted with multipart/form-data
import java.io.*;
import javax.servlet.ServletException;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import com.google.appengine.api.datastore.Blob;
// Fetch the attributes for a given model using rails conventions.
// We need to do this in Java because getParameterMap uses generics.
// We currently only support one lever: foo[bar] but not foo[bar][baz].
// We currently only pull the first value, so no support for checkboxes
public class ScopedParameterMap {
public static Map params(HttpServletRequest req, String model)
throws ServletException, IOException {
Map<String, Object> scoped = new HashMap<String, Object>();
if (req.getHeader("Content-Type").startsWith("multipart/form-data")) {
try {
ServletFileUpload upload = new ServletFileUpload();
FileItemIterator iterator = upload.getItemIterator(req); // this is used to get those params
while (iterator.hasNext()) {
FileItemStream item = iterator.next();
InputStream stream = item.openStream();
String attr = item.getFieldName();
if (attr.startsWith(model + "[") && attr.endsWith("]")) { // fetches all stuff like article[...], you can modify this to return only one value
int len = 0;
int offset = 0;
byte[] buffer = new byte[8192];
ByteArrayOutputStream file = new ByteArrayOutputStream();
while ((len = stream.read(buffer, 0, buffer.length)) != -1) {
offset += len;
file.write(buffer, 0, len);
}
String key = attr.split("\\[|\\]")[1];
if (item.isFormField()) {
scoped.put(key, file.toString());
} else {
if (file.size() > 0) {
scoped.put(key, file.toByteArray());
}
}
}
}
} catch (Exception ex) {
throw new ServletException(ex);
}
} else {
Map params = req.getParameterMap();
Iterator i = params.keySet().iterator();
while (i.hasNext()) {
String attr = (String) i.next();
if (attr.startsWith(model + "[") && attr.endsWith("]")) {
String key = attr.split("\\[|\\]")[1];
String val = ((String[]) params.get(attr))[0];
scoped.put(key, val);
// TODO: when multiple values, set a List instead
}
}
}
return scoped;
}
}
I hope this speedy answer helps, let me know if you have questions.