In JSF we can use
valueChangeListener attribute
or
<f:valueChangeListener type=""/>
to listen for ValueChange Events for Individual components.
Is there any way that i can apply the ValueChangeListner to group of
components or entire form?
Edit:
The basic idea is, There is a huge form of around 30
components[input-texts,text-areas,select-many-menu,select-one-menu.....]
and some of them will be pre-populated.
I want to notify the user whenever there is value change in any one component of this entire
form.
No. You can apply the same value change listener for multiple components, and you will need to handle it programatically
Related
I've searched google and stack but can't seem to find a definitive answer. What I would like to do, is something like this:
Say I have custom control A, within which, is a radio button, when I click it, I want it to grab a custom property that is set on custom control B, lets say compositeData.Name as an example. Can I do this?
If I give custom control B an ID, lets say ccB, can the radio button in custom control A do something like, getComponent("ccB").getValue().compositeData.Name so I can get the value of the property I passed into custom control B using the custom property 'Name'?
If its a straight no, at least I know to stop playing around with the idea! Thanks
Reaching from one control into the inside of another control would break component isolation. You might want to take a different approach:
Option a - client side:
Your control emits a JavaScript event that bubbles up until it reaches a parent element that contains the control you want to change (presumably the parent Dom element). There you set the property of that element.
Option b - server side:
As Urs suggested: bind both to a bean and handle the updates inside the bean
When a JSF form field is wired into an entity bean field (which is mapped to a DB field), each setter in the entity bean is called regardless of whether the user changed the form field value in the front end, i.e. the setters on unchanged fields are invoked the same as those that have changed but their new value is the same as the old value.
My question is simple: Is there a way to configure JSF to only call the setters mapped to the fields that have changed in the front end? The reason for this is that I have a requirement by which I have to detect deltas on every persist and log them, more about which can be read in this question.
Maybe I didn't understand you clearly, but why are you mapping directly your entity beans to a JSF view ?! IMHO it would be better if you add managed beans between your JSF pages and the entities in order to better separate your business logic from data access.
Any way, I think the easiest solution to impelement for that case is by making use of Value Change Events which are invoked "normally" after the Process Validations phase (unless you make use of the immediate attribute).
The good news about Value Change Events (regarding your example) is they are invoked ONLY after you force form submit using JavaScript or Command components AND the new value is different from the old value.
So, as an example on how to use value change listeners, you can add valueChangeListner attribute to each of your JSF tags like following:
<h:inputText id="input" value="#{someBean.someValue}"
valueChangeListener="#{someBean.valueChanged} />
Then, implement your valueChanged() method to look something like:
public void valueChanged(ValueChangeEvent event) {
// You can use event.getOldValue() and event.getNewValue() to get the old or the new value
}
Using the above implementation, may help you to separate your logging code (it will be included in the listeners) from your managed properties setters.
NB: Value Change Listeners may also be implemetend otherwise using the f:valueChangeListener Tag, but this is not the best choice for your example (you can find some examples in the section below, just in case)
See also:
Valuechangelistener Doubt in JSF
JSF 2 valueChangeListener example
When to use valueChangeListener or f:ajax listener?
I have two jsf custom-components which are supposed to communicate.
These components are a DataTable and a pager.
I am looking for that when changing the model of the DataTable, an event triggers to allow the pager to be updated, and vice versa. and that maintaining their independence. is it possible to do so using the listener and the event?
Yes, pass the pager as property of the listener or just let the pager itself implement FacesListener.
I am trying to implement an audit trail functionality for my web application that records:
lastModified (timestamp)
modifiedBy (user information)
userComment (reason for value change)
for each of my input fields (input fields are spread over several forms with different backing beans and different valueHolder classes).
The first two (lastModified and modifiedBy) are easily done with the help of an JPA AuditListener and #PrePersit and #PreUpdate methods.
The third one is a bit tricky since it requires user interaction. Best would be a dialog that asks for the user comment.
So there are (at least) two open issues: Can I establish a "global" valueChangeListener for all input fields in my application? Is this possible without attaching <f:valueChangeListener> to each single input component? Second: How can I grab the user comment. My idea is to put a p:dialog in my web page template but this dialog needs to know from which input component it is called.
Can I establish a "global" valueChangeListener for all input fields in my application? Is this possible without attaching to each single input component?
Yes, with a SystemEventListener which get executed during PreRenderViewEvent. You need to walk through the component tree as obtained by FacesContext#getViewRoot() to find all components which are an instanceofEditableValueHolder (or something more finer-grained) and then add the new YourValueChangeListener() by the addValueChangeListener() method. See also this answer how to register the system event listener: How to apply a JSF2 phaselistener after viewroot gets built?
Second: How can I grab the user comment. My idea is to put a p:dialog in my web page template but this dialog needs to know from which input component it is called.
You could in YourValueChangeListener#processValueChange() set the component in question as a property of some request or view scoped which you grab by evaluateExpressionGet().
Recorder recorder = (Recorder) context.getApplication().evaluateExpressionGet(context, "#{recorder}", Recorder.class);
recorder.setComponent(event.getComponent());
// ...
It will execute the EL and auto-create the bean in its scope if necessary. The bean in turn should also hold the property representing the user comment. Finally, you can use it in your <p:dialog>.
<p>You have edited #{recorder.component.label}, please mention the reason:</p>
...
<h:inputText value="#{recorder.comment}" />
I have a JSF 1.2 Form which is composed of several parts.
I have validation with required tag turned on.
I want to be able to clear a certain part of the form which has required fields so on the 'clear' button i used the immediate tag.
Now the challenge - When pressing the 'clear' button all the values that were filled since the last submission are restored to the last submitted state while I would like only the certain part of the form to be affected. (Meaning, all the values that are not in that part of the form should be sumbitted although the button pressed is immediate)
Is there a way to do this?
EDIT - Can I submit a value after every time it was filled? This might be a solution.
Thanks!
If you want to take some fields along with the cancel button with immediate="true", then you should also put immediate="true" on those fields.
If you want to skip validation on those fields as well, then you need to change required="true" to required="#{empty param['formId:cancelButtonId']}" so that it is only required when the cancel button is not been used to submit the form.
As to submitting the values on change, that's best to be achieved with ajax in combination with a value change listener. To achieve that you would need to upgrade to JSF 2.0 or to introduce an ajaxified JSF component library.