Generating code from UML models using AlphaSimple and StringTemplate

We just released a new build of AlphaSimple with basic support for customized code generation using templates, more specifically, using StringTemplate templates. Let’s take a quick tour:

Create a model in AlphaSimple

Create your model in AlphaSimple. If you need help with the notation, check the tutorial. You can just start with the default contents you get when creating a new project:

package NewProject;

class NewProject
    /* attributes */
    attribute text : String;
    attribute check : Boolean;
    attribute number : Integer[0,1];
    attribute date : Date[0,1];
    /* relationships */
    /* actions */
    operation toggle();
        self.check := not self.check;
    /* queries */


Remember to save your file.

Create a template

AlphaSimple supports StringTemplate as template language (check out this 5-minute introduction). In order to define a template in your AlphaSimple project, create a file with the .stg extension (in StringTemplate lingo, it is a template group file). You can use the example below, which for every class in a model, creates a text file that shows its name, and the names of its attributes and operations:

group simple;

outputPath(class) ::= <<
<! The 'outputPath' template is optional and determines the path of the file generated (the default is the class name) !>

contents(class) ::= <<
<! The 'contents' template is mandatory and is the entry point for generating the contents of the file from a class. !>
Class: <>

Attributes: <class.ownedAttributes:{attr|<>};separator=", ">

Operations: <class.ownedOperations:{op|<>};separator=", ">

Again, remember to save this file.

Declare your custom template

To enable custom templates, you need to create an AlphaSimple configuration file ( It is a configuration file that drives the compiler and code generation in AlphaSimple. Your file can be as simple as this:

# the template implementation we use

# the templates supported (always<name>.template=<template file name>

Both entries are mandatory. Ensure the line declaring the template matches the name you chose when creating the template file. Save this file.

Test your template

In order to test your custom template, if you have been using a guest account, you will need to sign up first (it’s free). Your project contents will be preserved.

First, publish your project (see button in the editor). Then, from your list of projects (“My Projects”), share your project (open lock button). For any future modifications to model, template or configuration file, you will need to publish your changes again. This will not be required in the future.

We are almost there. Since there is no UI for triggering custom generation yet, you will need to use the REST API, which is quite easy. Find out the numeric id of your project (from any link pointing to it). Then hit a URI with this shape:<username>-<project-id>/

For instance, for project 515, belonging to user simple, the URI would be:

which returns:

<workspace packageCount='1' timestamp='1298449947000'>
  <model name='NewProject.uml'
  <properties name='' uri=''/>
  <source name='NewProject' uri=''/>
  <source name='simple.stg' uri=''/>
  <generator platform="jpa" uri=""/>
  <generator platform="pojo" uri=""/>
  <generator platform="simple" uri=""/>
  <renderer uri=""/>

which gives you access to all the objects that AlphaSimple project has: source files (model and template), the configuration file, the generated UML model and corresponding class diagram, and, what we are mostly interested here, all generators available. Note that it includes not only a generator for the custom template, but some other built-in generators as well. But lets ignore those for now, and open the generator URI for our custom template (named “simple”). Voila, this is what you should see:

Class: NewProject

Attributes: text, check, number, date

Operations: toggle


We hope this very simple example gave you an idea of how you can generate code from UML models using AlphaSimple and StringTemplate (even if it doesn’t really generate actual code). In the example template, we only navigate from a class to its operations and attributes, and access their names, but your template has virtually any information from the underlying UML model available to generate from.

If you would like to see more interesting models and actual code generation templates, browse the shared project area. For now, there is currently just one project with an elaborate template. Clone it and model (and generate) away. If you have any feedback, just post a comment here or check the AlphaSimple contact page.

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