How to use ModelDriven in Struts 2 ?

Two ways to collect input for Actions :

1. Model-driven

• Action has methods returning your model classes (myAction.getUser())
• Fields in the view are fields of your model
• Views refer directly to your model (property=‘user.name’)
• Excellent because it allows model reuse

2. Field-driven

• Action has fields of its own, which are fields in the view
• execute() collates fields and interacts with the model
• Views refer to action fields (property=‘daysTillNextBirthday’)
• Useful where form is not parallel to model

The two can be mixed and used.

ModelDriven Interface

• Direct support of model-driven Actions
• The ModelDriven Interface has one method :
  public Object getModel()
• Properties of the model are flattened :
  “name” instead of “user.name”
• Applies to UI tags, form field names, and so forth

public class Birthday extends ActionSupport implements ModelDriven {

   ...

   public Object getModel() {

     return user;

   }

}

Applying the ModelDrivenInterceptor

In struts.xml

<action name=“birthday" class=“happy.Birthday">

  <interceptor-ref name="modelDriven"/>

  <interceptor-ref name="defaultStack"/>

  <result>/Model/success.jsp</result>

  <result name="input">/Model/form.jsp</result>

</action>

The ModelDrivenInterceptor pushes the Model onto the ValueStack.