What is ValueStack and how it is used ?

What is ValueStack ?

• The ValueStack builds a stack of objects.
• Objects are examined to find property values.
• The ValueStack allows the expression language to find property values across multiple objects.

How is the ValueStack used ?

• The Action instance is always pushed onto the ValueStack.
• The Model is pushed on by the ModelDrivenInterceptor.
• The UI tags use it to push values on during their scope and evaluate expressions.
• The s:iterator tag pushes the current item onto the stack.
• The s:bean tag pushes a bean instance on the ValueStack.
• The s:property tag evaluates an expression against the ValueStack.
  
  All tag attribute values are evaluated against the stack when being set onto the tag instances.