Description Will Smythe 2011-11-23 21:38:57 EST

Google App Engine (GAE) is a popular deployment environment (http://code.google.com/appengine/), especially for individual developers and small shops. It provides a Java servlet container and supports a set of services for data access, security, etc. More info can be found here - http://code.google.com/appengine/docs/java/runtime.html

I hacked around and was able to get a (non-database) RUI application to work. Here are the changes I had to make:

1) EGL JS runtime assumes the context root is some non-empty string, but GAE uses a "" for the context root. To fix, had to go into the generated HTML and set the egl__contextroot to "." 

2) GAE does not support apps spawning their own threads (http://code.google.com/appengine/docs/java/runtime.html#The_Sandbox), which is something the EGL Proxy does in HttpServiceHandler. To fix, had to update invokeRestService method to use a standard reader to read from the connection.
    BufferedReader reader = new BufferedReader(new InputStreamReader((ByteArrayInputStream)content));

3) ServiceServlet was expecting a non-null context root in its init() method, so had to add code to handle null appropriately: 		if (contextRoot == null || contextRoot.length() == 0) {
			System.out.print("setting context root to empty string");
			contextRoot = "";
		} else {
			while(contextRoot.charAt(0) == '/'){
				contextRoot = contextRoot.substring(1);
			}
		}
3)


I see this support happening in two stages:
* Stage 1 - support for deploying EGL apps that do NOT need database access (i.e. just RUIs and simple services)
* Stage 2 - support for deploying EGL apps that need database support (should use the data access/storage capabilities of GAE).

The deployment operation should support deploying directly into a GAE 'web' project (which is not a standard Eclipse Dynamic web project).