将带有发布请求的文件信息发送到Google Appengine

Question

I am trying to write a Google Appengine Post program that receive a file.

I observe that I get the content length of six bytes which is what the client sent. However, I cannot get the content. When I try to read from the getInputStream I get -1 the first time. (I also tried reading into a ByteArray of six bytes, and similarly, I get nothing in the buffer.)

package guestbook;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.http.*;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import java.util.logging.Logger;
public class XStore extends HttpServlet {
  public void doPost (HttpServletRequest req, HttpServletResponse resp) throws
     IOException {
    Logger log = Logger.getLogger(XStore.class.getName());
     String ct;
     ct=req.getContentType();
     resp.setContentType("text/plain");
     String key = req.getParameter("key");
     String value = req.getParameter("value");
     DatastoreService d = DatastoreServiceFactory.getDatastoreService();
     byte [] B;
     InputStream IS = req.getInputStream();
int i,le;
le = req.getContentLength(); 
StringBuffer rB = new StringBuffer();
int rv;
int c;
c = IS.read();
log.info("Srv = " + c ); 

This returns logs a -1 ... rest of program omitted for brevity My displays also indicated that le was six.

Here is the client

import java.net.*;
import java.io.*;
public class client {
public static void main (String a []  ) throws MalformedURLException,java.io.IOException,ProtocolException {
URL u = new URL("http://uthreee.appspot.com/XX?key=a&value=a");
HttpURLConnection H;
H = (HttpURLConnection) u.openConnection();
H.setRequestMethod("POST");
H.setDoOutput(true);
OutputStreamWriter w = new OutputStreamWriter(H.getOutputStream());
w.write("abc");
w.write("def");
w.close();
System.out.println(H.getResponseCode());
}}

Note that the response code is 200. Thanks for any insight. A student and myself spent over ten hours together trying to find a way to transmit an XML file to the Google Appengine, but cannot find a way to read the information sent by the client (which ultimately will be an Android App).

Dr. Laurence Leff Associate Professor of Computer Science, Western Illinois University, Macomb IL 61455 on sabbatical

Answer 1

For what it's worth, using a browser form containing an <input type="file">, the Apache Commons FileUpload definitely works with AppEngine. In my case the form seemed to require the enctype="multipart/form-data" attribute, and of course method="post".