A simple code generator example with FMPP and FreeMarker with the help of ant and antelope for automation.

Content :
– Why should we do code generators ?
– How it works
– Prepare ant tasks
– Let’s try with a simple file
– Now let’s do something bigger

Why should we do code generators
Some people are…pretty anxious when I advocate the use of a code generator. Most of the time they think spending time on a code generator isn’t productive enough for their short term objectives… These kind of person spend their lives running to catch a train that goes to fast for their capacity. Actually, code generators are a perfect answer for short term project, but not the first one (and again this isn’t obvious).

Code generators are part of your company’s (or personal) normalisation, industrialisation, and process simplification.
– Developers can focus more on business than technical implementation,
– Maintenance is easier : all code base is similar
– If your company turnover is important, process are simpler to acquire

So actually you can code faster, with a better quality, the ROI is always (if code generator is correctly done) positive.

How it works
Creating a code generator project is really fast, just :
1- use a real project you want to generate and copy it somewhere,
2- identify the dynamic stuff inside this project, like :
– classnames,
– packages,
– folders,
– …
3- replace dynamic patterns with a property tag
4- generate it once and do the adjustments if needed

In order to have an idea, a code generator creating around fifty files, that creates a Flex module with BlazeDS Java endpoints takes about 4 hours of work and tuning before beiing live.

Prepare ant tasks
Download Fmpp and AntelopeTasks jars and put them inside your ANT_HOME/lib folder.
Then inside your build.xml add those 2 lines after your project definition :

Now to use fmpp just do something like this inside a target :

Antelope in this project will be used mostly for its lowercase/upperCase/replace commands. Example :

Let’s try with a simple file

You can get the files here : QQ_CG01.tar

The src folder contains this hierarchy : fr/quidquid/sample/flex/modules/MODULE_CODE
This folder contains the ModuleConstants.as file.

Inside the ModuleConstants.as file you’ll find freemarker tags :

Our goal is to replace these tags and after generation rename the MODULE_CODE folder with the right name.

First step to see how it works, in the root folder open the PROJECT.properties, it contains our dynamic stuffs (quite simple on this example):

Then let’s look at the build.xml file:

You can now open a command line ant do:

Output should be something like:

Now you should have an OUT folder containing your fr/quidquid/sample/flex/modules/qqt01/ModuleConstants.as with all the freemarker tags replaced… Easy no ?

Some freeMarker expressions you can use:
${module_code?upper_case}
${module_code?lower_case}
${module_code?cap_first}

To change the name of a filename:
<@pp.dropOutputFile />
<@pp.changeOutputFile name=module_name?cap_first + "Mediator.as" />

Well just go through the manual: http://freemarker.sourceforge.net/docs/dgui_template_exp.html

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