Awesome

A tiny JavaScript web framework targeted for Google App Engine

Prototyping applications is as easy as writing some JSON:

var apejs = require("apejs.js");
apejs.urls = {
    "/": {
        get: function(request, response) {
            response.getWriter().println("Hello World!");
        }
    },
    "/foo": {
        get: function(request, response) {
            request.getSession(true);
        }
    },
    "/recipes/([a-zA-Z0-9_]+)" : {
        get: function(request, response, matches) {
            response.getWriter().println(matches[1]);
        },
        post: function(request, response) {
            // do something during POST request
        }
    }
}

Reaching http://yoursite.com/ will output Hello World!, accessing http://yoursite.com/foo will start a new session and going to http://yoursite.com/recipes/my-fantastic-recipe will show you my-fantastic-recipe.

You can leverage the entire Java API (Rhino) directly through JavaScript, avoiding re-compilation times in favor of raw scripting power!

Idea behind ApeJS

The idea behind ApeJS is to provide a tiny framework for developing Google App Engine websites using the JavaScript language. There are other JS frameworks out there that you could use with App Engine - RingoJS and AppEngineJS are extremely well made - but I needed something more simple, something that didn't come with tons of libraries and that could let me prototype applications really quickly (think of web.py) and so I created ApeJS.

How to start

1. Clone ApeJS by simply typing git clone git@github.com:lmatteis/apejs.git in a terminal.

2. Download the latest App Engine Java SDK from the App Engine website. Unzip, open the folder and navigate to the lib/user/ directory where you will find an appengine-api-1.0-sdk-x.x.x.jar file. Copy this jar file to the your war/WEB-INF/lib directory from within the ApeJS dir we cloned in the earlier step.

3. You're pretty much set. All you have to do is run dev_appserver.sh (or .cmd, found in the App Engine Java SDK) against the war directory of your ApeJS project.

4. The main file you need to worry about is main.js. This is where all the handlers for specific urls are called. The examples already in there should get you started.

5. An important folder you want to keep your eyes on is the /public/ directory. All your static content should go in here, stylesheets, images etc. So when you access http://yoursite.com/image.jpg the server will look inside /public/image.jpg for it.

Importing external JS files

Importing external JS files is quite easy thanks to require().

To include ApeJS modules (located under WEB-INF/modules/) you can do:

var googlestore = require("googlestore.js");

Otherwise you can include things from within your app directory by simply adding a ./ in front of the filename:

var myfile = require("./myfile.js");

require() will simply evaluate the contents of the JavaScript file and only expose whatever you assign exports with. This is how CommonJS implements so you could simply require CommonJS modules and they should work.

Some templating

will add some examples using mustache.js

Google Datastore

I'm trying to implement a really basic abstraction around the low-level Google datastore API. You can read the code under WEB-INF/modules/googlestore.js. In order to work with the datastore, first you need to include it in your file.

var googlestore = require("googlestore.js");

To create an entity and store it in the datastore you do:

var e = googlestore.entity("person", {
    "name": "Luca",
    "age": 25,
    "gender": "female",
    "nationality: "Italian"
});

// save the entity to the datastore
var key = googlestore.put(e);

You get an entity from the datastore by using a key:

// creating a key by ID
var key = googlestore.createKey("person", 15);

// get the entity from the datastore
var person = googlestore.get(key);

Listing more entities is done by using a query:

// selecting youngest 5 adult males as an array
var people = googlestore.query("person")
    .filter("gender", "=", "male")
    .filter("age", ">=", 18)
    .sort("age", "ASC")
    .fetch(5);

To get properties of an entity use the following method:

person.getProperty("gender");

Finally, there are a couple of key points to keep in mind when using the Datastore API:

• Filtering Or Sorting On a Property Requires That the Property Exists
• Inequality Filters Are Allowed on One Property Only
• Properties in Inequality Filters Must Be Sorted before Other Sort Orders

http://code.google.com/appengine/docs/java/datastore/queries.html

More to come ...