Struts2中的getContextMap（）和getValueStack（）之间的区别？

Question

Please tell what is the diffference between:

ValueStack stack=ActionContext.getContext().getValueStack();

and:

Map cont = ActionContext.getContext().getContextMap();

Answer 1

Value Stack (Taken from struts mailing list)

A value stack is essentially a List. Calling [1] on the stack, returns a substack beginning with the element at index 1. It's only when you call methods on the stack that your actual objects will be called.

Said another way, let's say I have a value stack that consists of a model and an action as follows:

[ model, action ]

here's how the following ognl would resolve:

[0] - a CompoundRoot object that contains our stack, [model, action]

[1] - another CompoundRoot that contains only [action]

[0].toString() - calls toString() on the first object in the value stack (excluding the CompoundRoot) that supports the toString() method

[1].foo - call getFoo() on the first object in the value stack starting from [OS:action] and excluding the CompoundRoot that supports a getFoo() method

ContextMap

ActionContext is the context in which an Action is executed. Each context is basically a container of objects an action needs for execution like the session, parameters, locale, etc.

ActionContext.getContext().getContextMap();

give you access to the context map in which your are executing.Say for example you need to access Application Context than you can get access to that using the Map returned by above method

Update As pointed by @rees

context map of the ActionContext is pretty much the backing (context) map of the ValueStack

Answer 2

getContextMap() - Method in class com.opensymphony.xwork2.ActionContext Gets the context map. This method gets the context map.

getValueStack() - Method in class com.opensymphony.xwork2.ActionContext Gets the OGNL value stack. This method gets the current value stack for this request and returns the value stack.For detail about this method .