Introduction #

If you ever wanted to create more custom Velocity Variables that would be available for your theme to reference it's as easy as setting an attribute in ServicePreAction.java!

Background #

If you look at the template code inside a typical Liferay theme, you will see many velocity variables being referenced. For example inside of the Classic theme's dock.vm, there is a line of code:

 <h2 class="user-greeting">
  <span>$user_greeting</span>
 <h2>

$user_greeting fetches the "Welcome Joe Bloggs" sign you'll see when you log in as test@liferay.com Where did $user_greeting come from? Look inside init.vm, and you'll that it's set here:

 #set ($user_greeting = $user.getGreeting())

It gets the User object ($user) and retrieves the 'greeting' (.getGreeting()) from the database. Where is the User object set as a velocity variable? The magic happens inside of VelocityVariables.java:

 vc.put("user", themeDisplay.getUser());

'vc' is an instance of VelocityContext, and all we are doing here is getting the user object (themeDisplay.getUser()) and assigning it the key of "user". This translates to the ability to using $user as the User object.

Custom Velocity Variables #

1. First see what variables are already available.
1. Some commonly used ones that are already available include $user, $company, $layout, and $themeDisplay. You probably don't want to create a new one for getting a user's screen name, because you can just do $user.getScreenName().
2. ServicePreAction.java
1. You'll want to extend the ServicePreAction class first and reference it in portal-ext.properties:

 servlet.service.events.pre=com.liferay.portal.events.ServicePreAction,your.custom.EXTServicePreAction

Inside your extended ServicePreAction class, create a Map object with the key and value of the vm variables you want to insert, and then set that into the attribute under the key WebKeys.VM_VARIABLES.

Finally, the WebKeys.VM_VARIABLES gets picked up in VelocityVariables.java:

 // Insert custom vm variables
 Map vmVariables = (Map)req.getAttribute(WebKeys.VM_VARIABLES);
 if (vmVariables != null) {
   Iterator itr = vmVariables.entrySet().iterator();
   while (itr.hasNext()) {
    Map.Entry entry = (Map.Entry)itr.next();
    String key = (String)entry.getKey();
    Object value = entry.getValue();
    if (Validator.isNotNull(key)) {
      vc.put(key, value);
    }
   }
 }