We do have a small page which is using the viewParam to convert a given Id to a concrete object. This converter is called on leaving (blur) of an inputText field, which is validated. Why? Could I rework this, so that the converter is not called every time?
This is annoying, because the converter calls the set-method for the corresponding object in the BackingBean and this bean is then null, if the page is called the first time for creating this object.
<f:metadata>
<f:viewParam name="id" value="#{bean.object}"
converter="#{objectConverter}"
converterMessage="#{msgs['converter.msg.object']}"/>
<f:viewAction action="#{bean.init}"/>
</f:metadata>
<p:inputText id="text" value="#{cc.attrs.value}"
styleClass="inputTextValidated"
required="#{cc.attrs.required}"
requiredMessage="#{cc.attrs.requiredmessage}"
label="text" validatorMessage="#{cc.attrs.msg}" title="#cc.attrs.title}"
readonly="#{cc.attrs.readOnly}">
<cc:insertChildren/>
<p:ajax update="msg_text" event="blur"/>
</p:inputText>
<p>
<p:message id="msg_text" for="text" display="msg"/>
</p>
If we do not use a converter but just the viewAction to convert the Id to the corresponding object (or create a new object if applicable), everything is fine. Is this the only/correct solution for this problem?
We do use primefaces 6.1 with CDI. The converter is a #Named and #ApplicationScoped bean implementing the Converter Interface.
Using p:fragment around the inputtext-field did not help either.
That is the nature of how JSF works. If you want to not have it do that I suggest you check out OminFaces ViewParam: http://showcase.omnifaces.org/components/viewParam
From their documentation:
Stateless mode to avoid unnecessary conversion, validation and model
updating on postbacks The standard UIViewParameter implementation
calls the model setter again after postback. This is not always
desired when being bound to a view scoped bean and can lead to
performance problems when combined with an expensive converter. To
solve this, this component by default stores the submitted value as a
component property instead of in the model (and thus in the view state
in case the binding is to a view scoped bean).
The standard UIViewParameter implementation calls the converter and
validators again on postbacks. This is not always desired when you
have e.g. a required="true", but the parameter is not retained on form
submit. You would need to retain it on every single command
link/button by . To solve this, this component doesn't call
the converter and validators again on postbacks.
Related
I'm using an <f:viewParam> to pass a parameter as follows.
<ui:define name="metaData">
<f:metadata>
<f:viewParam name="id" value="#{bean.entity}" converter="#{converter}"/>
</f:metadata>
</ui:define>
Is it possible to process this <f:viewParam>, only when the page is loaded/refreshed?
It is just because the converter as specified with the <f:viewParam> is costly that converts the value passed through the query-string to a JPA entity. Hence, it involves an expensive database transaction, even when doing ajaxical postbacks using components like <p:commandButton>, <p:commandLink> which is unnecessary.
So, when for example, a <p:commandLink> (ajaxical) is clicked, the expensive business service (in the converter) should not be executed. Can this be done?
This somehow works (strange enough nevertheless), when the rendered attribute is evaluated against facesContext.postback like rendered="#{not facesContext.postback}" but the attribute rendered is not documented. Hence, it is unreliable.
You can achieve this by creating a custom tag extending <f:viewParam> wherein you store the submitted value as an instance variable which isn't stored in JSF view state instead of in the JSF view state as the <f:viewParam> by default does. By end of request, all UI component instances are destroyed. They are recreated in beginning of the request. When submitted value is null, then it won't call the converter nor the model setter. This all is elaborated in Arjan Tijms' blog.
OmniFaces offers already since version 1.0 a ready to use solution in flavor of <o:viewParam>, see also my own blog on that. Based on your question history, you're already using OmniFaces, so all you basically need to do is to replace f: by o:.
<ui:define name="metaData">
<f:metadata>
<o:viewParam name="id" value="#{bean.entity}" converter="#{converter}"/>
</f:metadata>
</ui:define>
This won't call the model setter (nor the converter) during postbacks on the same view.
This somehow works (strange enough nevertheless), when the rendered attribute is evaluated against facesContext.postback like rendered="#{not facesContext.postback}" but the attribute rendered is not documented. Hence, it is unreliable.
That's because the <f:viewParam> is in essence an UIInput component (else it wouldn't be able to perform conversion, validation, model-update and all that stuff like usual input components) which is thus just an UIComponent supporting a rendered attribute. This is however not explicitly documented as it actually doesn't render anything to the HTML output (that's also why it's a f:xxx, not a h:xxx). But with this attribute you can actually control the behavior during postback as this attribute is also evaluated in processDecodes() method which is invoked during apply request values phase.
I would like to use a few #RequestScoped beans to make some simple business logic on my entities. In their #PostContruct method, I obtain the id of the entity from the request parameters map.
This kind of setup works well for creating streamed graphics contents, using something like the following (in this case part of a composite component):
<p:graphicImage value="#{myRequestScopedBean.picture}" >
<f:param name="entityId"
value="#{cc.attrs.value.id}" />
</p:graphicImage>
However, the <f:param> tag does not seem to work for all components. For instance, how am I supposed to pass them in a <ui:repeat>, <c:set>, or to call my bean method for any of the other attributes than value?
I'm using an <f:viewParam> to pass a parameter as follows.
<ui:define name="metaData">
<f:metadata>
<f:viewParam name="id" value="#{bean.entity}" converter="#{converter}"/>
</f:metadata>
</ui:define>
Is it possible to process this <f:viewParam>, only when the page is loaded/refreshed?
It is just because the converter as specified with the <f:viewParam> is costly that converts the value passed through the query-string to a JPA entity. Hence, it involves an expensive database transaction, even when doing ajaxical postbacks using components like <p:commandButton>, <p:commandLink> which is unnecessary.
So, when for example, a <p:commandLink> (ajaxical) is clicked, the expensive business service (in the converter) should not be executed. Can this be done?
This somehow works (strange enough nevertheless), when the rendered attribute is evaluated against facesContext.postback like rendered="#{not facesContext.postback}" but the attribute rendered is not documented. Hence, it is unreliable.
You can achieve this by creating a custom tag extending <f:viewParam> wherein you store the submitted value as an instance variable which isn't stored in JSF view state instead of in the JSF view state as the <f:viewParam> by default does. By end of request, all UI component instances are destroyed. They are recreated in beginning of the request. When submitted value is null, then it won't call the converter nor the model setter. This all is elaborated in Arjan Tijms' blog.
OmniFaces offers already since version 1.0 a ready to use solution in flavor of <o:viewParam>, see also my own blog on that. Based on your question history, you're already using OmniFaces, so all you basically need to do is to replace f: by o:.
<ui:define name="metaData">
<f:metadata>
<o:viewParam name="id" value="#{bean.entity}" converter="#{converter}"/>
</f:metadata>
</ui:define>
This won't call the model setter (nor the converter) during postbacks on the same view.
This somehow works (strange enough nevertheless), when the rendered attribute is evaluated against facesContext.postback like rendered="#{not facesContext.postback}" but the attribute rendered is not documented. Hence, it is unreliable.
That's because the <f:viewParam> is in essence an UIInput component (else it wouldn't be able to perform conversion, validation, model-update and all that stuff like usual input components) which is thus just an UIComponent supporting a rendered attribute. This is however not explicitly documented as it actually doesn't render anything to the HTML output (that's also why it's a f:xxx, not a h:xxx). But with this attribute you can actually control the behavior during postback as this attribute is also evaluated in processDecodes() method which is invoked during apply request values phase.
Is there a way to do pass an input value as a action's parameter without using managed properties?
i.e.
<h:form>
<h:inputText id="input" />
<h:commandButton action="#{someBean.doSome(input)}" />
</h:form>
Yes, it's during the form submit already there in the JSF component state. Just bind the input component to the view by binding attribute, which will reference an UIInput instance, which in turn has a getValue() method for the very purpose of retrieving the input value (so that you can pass it as action method argument):
<h:form>
<h:inputText ... binding="#{input}" />
<h:commandButton ... action="#{someBean.doSome(input.value)}" />
</h:form>
The properness of this approach is however highly questionable and depends on concrete functional requirements. This approach is namely basically tight-coupling the view with the model and therefore considered a bad practice.
See also:
How to send form input values and invoke a method in JSF bean
How does the 'binding' attribute work in JSF? When and how should it be used?
Is there a defined behaviour in JSF, if two input fields are bound to the same session scoped Backing Bean property.
Here is my code snippet
<h:form id="myForm">
<h:inputText id="field1" value="#{TheBackingBean.theProperty}" />
<h:inputText id="field2" value="#{TheBackingBean.theProperty}" />
<h:commandButton id="continueButton" action="#{TheBackingBean.doSomething}" />
</h:form>
My question: If field1 and field2 receive different values, what will be bound to the backing bean property? Is this even allowed?
I know this is a crude scenario. My motivation is, that we have htmlunit tests running for our application. In our JSF application we want to use a cool ajaxified custom component. This doesnt work together very well with htmlunit. So my idea was, I just put in a hidden field that binds to the same property. The unit test then fills the hidden field instead of the "real" thing.
Regards
I think this kind of code is allowed, but I am not sure of the value of theProperty after the submission. What I think is that JSF will do the following:
TheBackingBean.setTheProperty(field1.value);
TheBackingBean.setTheProperty(field2.value);
However, nothing - as far as I know - specifies the order of the setter calls. Thus, after the update values JSF phase, you will not be sure if theProperty will be equal to field1.value or field2.value.
Concerning your scenario, you say that you want to bind the same property to an inputText and an hiddenText. As the hiddenText will not submit its value, unlike the inputText, this problem will not occur. Indeed, if you have this kind of JSF code:
<h:inputText id="field1" value="#{TheBackingBean.theProperty}"/>
<h:inputHidden id="field2" value="#{TheBackingBean.theProperty}"/>
then JSF will only do:
TheBackingBean.setTheProperty(field1.value);
during the submission phase.