Google AppEngine

To get the development environment working the plugin also requires access to the unzipped SDK as packaged by Google. The plugin tries to help you set this up (“gae:unpack”) but that failed for me. I was able to get stuff working by manually unzipping the SDK artifact downloaded directly from Google to the following directory: ~/.m2/repository/com/google/appengine/appengine-java-sdk/1.3.0/appengine-java-sdk-1.3.0

You’ll also notice in our appengine-web.xml that we substitute in our application name. By default this comes from the properties section of the pom.xml file (line 11).

Cron jobs / task queues Instead of using a framework like Quartz to schedule jobs, Google App Engine takes care of executing jobs for you. You simply enter a cron-like expression and a URL to call and your job is configured. You also have a task queue at your disposal. Your application code can add tasks to a task queue which will be executed later in the future, asynchronously. An example use case is that you don’t want clients to wait for an email to be sent before he sees the next page. Instead you can put the email task on the task queue and the email will be sent asynchronously.

When an email is received Google App Engine does a post on an URL in your application you configured. The HTTP body of the POST request contains the exact mime message as it was received by Google. To parse this mime message you can use the MimeMessage class provided by the JDK.

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

you could leverage Entity's getProperties() method, in combination with JSON-lib's groovy-friendliness and ability to serialize maps as JSON. So, say you have an Entity: def person = new Entity("person") person.name = "Guillaume Laforge" def jsonString = person.properties as JSONObject Have a look at JSON-lib and the Entity JavaDoc. And I think it'll solve your problem pretty neatly!

you can use the sample project that the google plugin for eclipse create for you. Then you can easily replace the generated java code by groovy / gaelyk code. Note that you need to add the jars in the war/WEB-INF/lib of your project, and add them in the project build path options.

! In this blog post we learn how easy it is to deploy a simple Groovlet to the Google Appengine and how easy it is to parse JSON results.