ActionListener and Navigation Problem

An ActionListener does not return a String. However, an action method does. =)

This is a very easy thing to misunderstand about commandButtons and commandLinks. There are two ways to directly execute some actions after a submit click: ActionListener and action method. So lets talk about the differences.

The action method does not accept an ActionEvent. In fact, it doesn't accept any parameters at all, but it does return a String. The String returned from an action method is used in the faces-config.xml to determine the next page to view. Typically, the actions that happen in an action method are done to determine what page should be viewed next and to configure the state for the next page (if necessary).

The ActionListener does accept an ActionEvent, but doesn't return a String. An ActionListener does not get to determine the next page to be viewed. Instead, it performs any miscellaneous actions that you might need to execute after a "submit" click. ActionListeners can be used to configure the state for the next page... But typically, it really is for miscellaneous operations. For example, I have an application with an ActionListener that performs some logging of the current status of my app.

On the commandLink/Button, the action method is tied to the action attribute and the ActionListener is tied to the actionlistener attribute. If you do not need to determine the next page, or setup the application for the next page, then you can simply supply a String to the action attribute. i.e. action="questionTemplate". If you do that, you do not need to create an action method.

Hope this helps,

CowKing

IamCowKinga at 2007-7-12 3:24:43 >

my friend an action listener method is always called before action method.always remeber whenever an event is throw it would be handled by eventListener method first and then control is transferred to the other methods.

Therefore what ever changes you wanna do the your MODEL layer you can.Utilmately the action method is called to returned by action method as an outcome to fwd/redirect the page to another...

here is an example for you

Sample JSP View:

==============

<f:view>

..............................................

...............................................

..............................................

...............................................

<h:form>

................................................

...............................................

..............................................

...............................................

..............................................

...............................................

<h:commandButton actionlistener="#{UiBean.actionListen}" action="#{UiBean.action}" value="Sample Button" />

..............................................

...............................................

..............................................

...............................................

</h:form>

................................................

...............................................

</f:view>

ManagedBean:

============

public class UiManagedBean{

private String property;

.............................................

.............................................

.............................................

.............................................

.............................................

.............................................

.............................................

public void actionListen(ActionEvent ae){

/*

calling model layer or requesting for a specific service from model

and updating model accordingly

*/

//first get the question ID,questionType ,Question and Releated Answers

String surveyQuestionID = (String) event.getComponent().getAttributes().get("surveyQuestionID");

System.err.println("the question id is :"+surveyQuestionID);

String surveyQuestionDesc = (String) event.getComponent().getAttributes().get("surveyQuestionDesc");

String questionType = (String) event.getComponent().getAttributes().get("questionType");

ArrayList surveyQuestionList = (ArrayList) event.getComponent().getAttributes().get("surveyQuestionList");

Iterator it = surveyQuestionList.iterator();

while(it.hasNext()){

SelectItem selectItem = (SelectItem)it.next();

this.setAnswer(selectItem.getLabel());

this.setAnswer("\n");

}

this.setQuestion(surveyQuestionDesc);

this.setSelectedType(questionType);

}

public String action(){

....................................

.....................................

....................................

return "questionTemplate";

}

.............................................

.............................................

.............................................

.............................................

}

faces-config.xml:

==============

<navigation-rule>

<managed-bean-name>UiBean</managed-bean-name>

<managed-bean-class>UiManagedBean</managed-bean-class>

<managed-bean-scope>request</managed-bean-scope>

<navigation-case>

<from-outcome>questionTemplate</from-outcome>

<to-view-id>/content/questionSelection.jsp</to-view-id>

</navigation-case>

</navigation-rule>

Hope that might Help :)

REGARDS,

RaHuL

RahulSharnaa at 2007-7-12 3:24:43 >