At a high level, how does struts2 work? I'm co

Question

At a high level, how does struts2 work? I'm coming from a mvc background

Looking at a sample project, I see allot of these ___action type classes.

Is it just a action references to a controller action? i.e. a response to a particular url based on get/post?

Answer 1

Typical Struts2 workflow (bear in mind that Struts2 is extremely configurable, its parts are well decoupled)

struts.xml => defines 'mappings' :

• which action is executed for each URL
• one or more results : which resource (typically a JSP) generates the view for each result returned by the action

Hence, for example, say a struts.xml contains

   <action name="add" class="example.SumAction">
     <result name="error">/Error.jsp</result>
     <result name="success">/SumResult.jsp</result>
   </action>

And your Java action is:

   public class SumAction { 
       private int x;
       private int x;
       private int z;
       // getters and setters ommited
       public String execute() {
           z = x + y; 
           return "success";
       }
   }

Then the request http://mysite.com/mywebapp/add.action?x=10&y=20 would make Struts2 to instantiate a SumAction object, set the x and y properties and call the execute method. If "success" is returned, then it will place the action in some "scope", forward to "/SumResult.jsp" in which typically one use some struts2 tag to show the result, pulling it from the action object.

 Result: <b><s:property value="z" /></b>

Of course, in less trivial scenarios the execute() method would call the service layer.

So, it's not very clear if the action is controller or controller+model, I'd say the later, because it not only has the logic to process the request but also acts as a container of the data (input and result). But only during the scope of a request.

Answer 2

The way I always understood it is that actions are your controllers. You hit a url, you map it to an action, your action controls what business logic happens, like "load domain object" or "just go to jsp".

The jsps are your views. I think if you are building a RIA where actions are handling xhrs and returning json, The V component of MVC is outside the framework -- its your extjs or whatever you are using for presentation.

Struts has always seemed like really a VC framework, because you don't define your model with struts. You do that yourself. Although you use the model in struts, when you convert your model to whatever your presentation needs.