Why ModelDriven not working?

[Daniele De Rossi]

My action class has 2 different methods which return each different Bean class.
This action class is mapped in strusts.xml like this;


==struts.xml==

<action name="Beans" class="Myaction" method="doSomething">
<result>result_mybean.jsp</result>
</action>

<action name="Beans" class="Myaction" method="doSomething2">
<result>result_mybean2.jsp</result>
</action>


==Myaction.java==

...implements ModelDriven, Prepare {

private MyBean bean;
private MyBean2 bean2;


public String doSomething() {
bean= new MyBean ();
...
setMyBean(bean); // <--this setter will push the bean to the valuestack.. right???

return SUCCESS;
}

public String doSomething2() {
bean2 = new MyBean2();
...
setMyBean2(bean2);

return SUCCESS;
}


public Object getModel() {
return null; //<-- It returns null because setter() will push the beans to the valuestakc..
}
public void prepare() {
//does nothing..
}

//...getters & setters of MyBean, MyBean2
...
}//end of MyAction




And I try to access to the propery of MyBean class in JSP

==result_mybean.jsp==
...
<s:property value="mybeanProperty" />

But it doens't work!

And this does work!
<s:property value="bean.mybeanProperty" />

I think I could access to the property without a class name due to the modeldriven interface and interceptor(in default interceptor Stack).

Teach me what I'm thinking wrong..



+)...I wonder that one action class should play only one role.

Or related tasks(like view, list, delete, update a Bean) can be together in one action class.

How you guys doing about action class??

[Ankit Garg]

Daniele you are not using the ModelDriven correctly. Calling setMyBean or setMyBean2 will not push the objects on the value stack. Actually after the action is finished processing, the whole action class object is added to the value stack. The bean properties of the action can then be used directly (like accessing bean2 calls getBean2 in the action class). ModelDriven is generally used with forms so that form values are automatically set with the property name and the bean name is not required. If you just want to access the properties of the bean without using the bean name, then you can manually push it on the value stack. In the JSP you can use the s:push tag to do this...

[David Newton]

Also, please UseCodeTags when posting code or configuration. Unformatted code and configuration is unnecessarily difficult to read. You can edit your post by using the button.

[Daniele De Rossi]

I figured out how to use ModelDriven exactly by now, sorry.

I had to do like this;

public Object getModel() {
	return bean;
}
public void prepare() throws Exception {
	bean = new MyBean();
	//...some logic
}

This works well with MyBean class.(Can get access to the property without a class name)

But as I said, two different methods is mapped in struts.xml


==struts.xml==

<action name="Beans" class="Myaction" method="doSomething"> 
  <result>result_mybean.jsp</result> 
</action> 

<action name="Beans" class="Myaction" method="doSomething2"> 
  <result>result_mybean2.jsp</result> 
</action> 

And each result page tries to do with different beans class.

So, getModel() and prepare() have to work different depends on which method was called.

I mean when doSomething() is called, getModel() and prepare() must do with MyBean class.

And when doSomething2() is called, getModel() and prepare() must do with MyBean2 class.

Is it possible??

This is why I asked you before post, one action must do one task or can do many related tasks.

I hope you all understand what I mean..

(Thanks for you tips, David Newton)

[David Newton]

Use a parameter to name the class, use a factory that's injected into the action, etc.

[Daniele De Rossi]

I tried to make object instance by class.forName(). I didn't do the Factory Pattern because I want to simplify the problem.

And faced a problem.It seems that the methods call sequence like this;

prepare()(by Prepare Interceptor) -> ... -> getModel() -> execute() or other methods mapped in struts.xml(doSomething() in here)

Because prepare() is called before doSomething(), there's no way to know the class.forName() in prepare();

... implements ModelDriven<Object>, Preparable	{
	private Object object;
	public String doSomething() throws Exception	{
		object = MyDAO.returnMyBean();
		
		return SUCCESS;
	}
	public void prepare() throws Exception {
		Class c = Class.forName(object.getClass().getName()); //<- getClass() throws NullPointerException
		object = c.newInstance();
	}

getClass() throws NullPointerException because object is null.

I don't know when and where to create object instance..

And get back to my last question, Do I have to create each actions on each tasks?(action1 does the MyBean1, action2 does the MyBean2...)?

[David Newton]

You can re-order or re-call interceptors as necessary (for example, see the prepareParamsPrepare stack).