Passing plugin objects to a workflow from JAVA

I am trying to understand how to pass objects to the Orchestrator API from the JAVA code sample found in the VMware Vsphere 5.5 Documentation Center in order to run workflows (ultimately from web pages).   

Are there examples of creating the execution context that use object input parameters (other than "String")? 

For instance, to enable or disable an AD user, the "Disable/Enable a User" workflows require an input parameter of "AD:USER".  How would you pass this parameter to the workflow in the JAVA code line:

"ExecutionContext context = new ExecutionContextBuilder().addParam(...).build();"