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Editorial Team
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Asked: 2026-06-09T16:09:55+00:00

Hi i am new to google app engine. i go through this tutorial I

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Hi i am new to google app engine. i go through this tutorial

I run these sample projects successfully.in this i have to upload a file and then it return back the same file.but i have given a url using this url i have to upload a file to blobstore.then downloading it again.
can any one please help how to upload a file through a url.
here is code for index.jsp file

<%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %>
<%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %>

<%
    BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
%>


<html>
    <head>
        <title>Upload Test</title>
    </head>
    <body>
        <form action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data">
            <input type="text" name="foo">
            <input type="file" name="myFile">
            <input type="submit" value="Submit">
        </form>
    </body>
</html>

here is serve.java code

package org.ritesh;
import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.appengine.api.blobstore.BlobstoreServiceFactory;

public class Serve extends HttpServlet {
    private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();

public void doGet(HttpServletRequest req, HttpServletResponse res)
    throws IOException {
        BlobKey blobKey = new BlobKey(req.getParameter("blob-key"));
        blobstoreService.serve(blobKey, res);
    }
}

UploadServlet code is here

package org.ritesh;

import java.io.IOException;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.appengine.api.blobstore.BlobstoreServiceFactory;

public class UploadServlet extends HttpServlet {

    private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();


    public void doPost(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException {

        Map<String, BlobKey> blobs = blobstoreService.getUploadedBlobs(req);
        BlobKey blobKey = blobs.get("myFile");

        if (blobKey == null) {
            res.sendRedirect("/");
        } else {
            res.sendRedirect("/serve?blob-key=" + blobKey.getKeyString());
        }
    }
}

it is running fine please suggest any modification so that it upload a file throught a url

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1 Answer

  1. Editorial Team

    If you want users to post a file to your own URL then you’ll need to use the Files API to write to the blobstore.

    However it is probably better to use the method you already have working to handle uploads if you can. It allows for larger files to be uploaded, and is most likely more efficient as the upload is handled by Google infrastructure rather than an instance of your application.

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