JSF drop down problem

[Nareshkumar Kapilavai]

Hi,
Iam very new to the JSF, i developed the page with two dropdown boxes(using selectOneMenu tags).my aim is when the user select the value of the first dropdown,the second dropdown should show the coresponding values for the first drop down selected value. for this i used valueChangeListener attribute and i wrote some methode to add coresponding values to the list for the specific selection. if i clicks on the submit button first time it is working fine and going to success page.second time it is throwing some "java.util.NoSuchElementException". i am using <managed-bean-scope>request</managed-bean-scope> in faces-conifg.xml,insted of this if i use <managed-bean-scope>session</managed-bean-scope> it is working fine but second dropdown is not refreshing. it is showing all the values.not showing only the values for the sfecific selection. my jsf code is :


<h:outputText value="Project:" />
<h:selectOneMenu id="projectName" value="#{projectDetails.projectName}" styleClass="ComboBoxBig"
valueChangeListener="#{projectDetails.projectChanged}" immediate="true" onchange="submit()">
<f:selectItems value="#{projectDetails.allProjects}" />
</h:selectOneMenu>
<h:outputText value="Location:" />
<h:selectOneMenu id="locationName" value="#{projectDetails.locationName}" styleClass="ComboBoxBig" >
<f:selectItems value="#{projectDetails.allLocations}" />
</h:selectOneMenu>
<h:commandButton id="submit" action="#{projectDetails.action}" value="Submit"/>

please suggest me to solve this problem. and please refer some documents on jsf to learn quickly.

Thanks&Regards!
Naresh kumar Kapilavai.

[Srivatsa Katta]

Originally posted by Nareshkumar Kapilavai:

<h:selectOneMenu id="projectName" value="#{projectDetails.projectName}" styleClass="ComboBoxBig"
valueChangeListener="#{projectDetails.projectChanged}" immediate="true" onchange="submit()">
<f:selectItems value="#{projectDetails.allProjects}" />
</h:selectOneMenu>

Could you please explain what is the purpose of onchange="submit()", i could get that valueChangeListener is for filtering the values of the next drop down, but why is onchange event ??

Regards,
Srivatsa Katta

[Nareshkumar Kapilavai]

i thought it is required to add javascript event to call that listener.and i am also not sure about this. cause it is not calling that methode with out writing that onChange = "submit()"..

[Gabriel Claramunt]

If you use "request" scope, you'll loose all the bean values each time the page is refreshed. The onChange="submit()" submits the page when the value has changed, immediate="true" skips the validations (you don't want to validate the other fields when you change the combo box).
Make sure the screen values are refreshed while on the changeListener (I'll post an example later)

BTW, feel free to check my blog (I had a paper introducing the JSF framework)

[Nareshkumar Kapilavai]

Hi,
Thank you very much.

[Gabriel Claramunt]

Here is an example of parent-child selection with multiple child selection, and the list of childs is not rendered until a parent is selected...

In the JSF page:

...
<h:selectOneMenu id="parent" immediate="true"
value="#{BackingBean.selectedParent}"
valueChangeListener="#{BackingBean.changeParent}"
        onchange="submit()" >
 <f:selectItems value="#{BackingBean.parentsList}"/>
</h:selectOneMenu>
...
 <h:selectManyListbox id="childs"
value="#{BackingBean.selectedChilds}"
rendered="#{BackingBean.parentId !=-1 }"
size="4" >
<f:selectItems value="#{BackingBean.childsList}"/>
</h:selectManyListbox>
...

In the backing bean:

...
 public void changeParent(ValueChangeEvent event)
 {
   Long parentId = (Long) event.getNewValue();
   selectedChilds=new Long[0];
   childList = getChildList(parentId);
 }
...

[ June 19, 2007: Message edited by: Gabriel Claramunt ]

[Nareshkumar Kapilavai]

Hi,
thanks to all.
naresh.