Group items tagged

for Java developers, there is a remote API handler available; adding following to your web xml file should work (disclaimer: I have not yet personally tested this.) <servlet>   <servlet-name>remoteapi</servlet-name>   <servlet-class>com.google.apphosting.utils.remoteapi.RemoteApiServlet</servlet-class> </servlet> <servlet-mapping>   <servlet-name>remoteapi</servlet-name>   <url-pattern>/remote_api</url-pattern> </servlet-mapping> <security-constraint>   <web-resource-collection>     <web-resource-name>remoteapi</web-resource-name>     <url-pattern>/remote_api</url-pattern>   </web-resource-collection>   <auth-constraint>     <role-name>admin</role-name>   </auth-constraint> </security-constraint>

How do I handle multipart form data? or How do I handle file uploads to my app? You can obtain the uploaded file data from a multipart form post using classes from the Apache Commons FileUpload package. Specifically you may want to use FileItemStream, FileItermIterator and ServletFileUpload as illustrated below. If you see a java.lang.NoClassDefFoundError after starting your application, make sure that the Apache Commons FileUpload JAR file has been copied to your war/WEB-INF/lib directory and added to your build path. 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

GaeVFS is an Apache Commons VFS plug-in that implements a distributed, writeable virtual file system for Google App Engine (GAE) for Java. GaeVFS is implemented using the GAE datastore and memcache APIs. The primary goal of GaeVFS is to provide a portability layer that allows you to write application code to access the file system--both reads and writes--that runs unmodified in either GAE or non-GAE servlet environments.

Yes, worker would be a servlet which can handle a request with POST parameters. If you want an asynchronous call from client's point of view then RPC is enough (from server's point of view it is still synchronous). If you want to do "delayed" jobs which don't talk to your client, you can use a task queue.

Instead of trying to create a thread (which is impossible in App Engine), this is a great way to asynchronously run tasks.

The easiest way to get setup rapidly is to download the template project from the download section. It provides a ready-to-go project with the right configuration files pre-filled and an appropriate directory layout: web.xml preconfigured with the Gaelyk servlets appengine-web.xml with the right settings predefined (static file directive) a sample Groovlet and template the needed JARs (Groovy, Gaelyk and Google App Engine SDK)

Running your application locally Google App Engine provides a local servlet container, powered by Jetty, which lets you run your applications locally. If you're using the Gaelyk template, when you're at the root of your project — and we assume you have installed the App Engine SDK on your machine — you can run your application with the following command-line: dev_appserver.sh war

Deploying your application in the cloud Once you're at the root of your application, simply run the usual deployment command: appcfg.sh update war

Google app engine uses the concept of static files. This is a performance optimization. Using the file appengine-web.xml you can configure the way google handles static files. You can include and exclude certain files using their extension or name. More information can be found here at google. This all works nice in the online version, however there seems to be a problem with the development server. Some solutions try to configure the local version as well, still that did not work for me. I decided to look for a servlet that serves static files.

That is it, now you can test your stuff locally and all your scripts, images, styles are loaded by your application. Of course you have to remove this servlet before uploading your application. Hope it helps people with their local debugging of jquery scripts or other javascript things.

Just set up remote_api for your app using the directions here - notably the tip: Tip: If you have a Java app, you can use the Python bulkloader.py tool by installing the Java version of the remote_api handler, which is included with the Java runtime environment. The handler servlet class is com.google.apphosting.utils.remoteapi.RemoteApiServlet. Then, use the Python bulkloader with --dump or --restore.

Tip: If you have a Java app, you can use the Python bulkloader.py tool by installing the Java version of the remote_api handler, which is included with the Java runtime environment. The handler servlet class is com.google.apphosting.utils.remoteapi.RemoteApiServlet.

I figure it is going to take me at least four iterations to get this right. The first one will be building a GWT application with a simple UI that has no server logic behind it (just to learn how layout in GWT works). Step two will be adding a fake servlet backend (not app engine, just in memory). While not exactly App Engine yet, I should have a completely specified client-server API by the end of this process that I can subsequently implement on App Engine (iteration 3). Iteration four will handle deployment, CSS and whatever I may screw up in iterations one and two. I will log my notes of things I run into while I code.

GaeVFS ships with a servlet that handles file uploads and abstracts how it writes them to its virtual file system. 

GaeVFS is built on top of Apache Commons VFS, and you use their FileObject instead of the standard File class.  There are some examples on the GaeVFS wiki, but I had to play around for a bit before I figured out some of the differences I needed to know. 

One thing you get used to on appengine is that any bulk data work requires the task queue.  You can use a little bit of framework and make all of these transforms (including deleting data) a question of just writing a simple task class and firing it off.  You'll want a copy of the Deferred servlet: http://code.google.com/p/gaevfs/source/browse/trunk/src/com/newatlant... Fair warning:  I found that I needed to change the code to make it perform base64 encoding all the time, not just on the dev instance.

One thing you get used to on appengine is that any bulk data work requires the task queue.  You can use a little bit of framework and make all of these transforms (including deleting data) a question of just writing a simple task class and firing it off.  You'll want a copy of the Deferred servlet: http://code.google.com/p/gaevfs/source/browse/trunk/src/com/newatlant... Fair warning:  I found that I needed to change the code to make it perform base64 encoding all the time, not just on the dev instance.

You must have two things in consideration: the appid and version must match, and you should enable datastore writes.

Please support the ability to server static files from the runtime based on regex patterns similar to the current Python runtime. Currently the only way to simulate this functionality is with a servlet. This is not ideal peformance, as evidenced by existing special handling of static files. The most compelling use case is for versioning static files with the app's version ID so that browsers can maximally cache static files without experiencing stale caches later when the app is updated.