I am working on an xhtml page that containt one very big form.
Within this form there is a loop driven from database results. Each row returned has a corresponding fragment which contains form inputs contributing to the outer form.I have wrapped this entire structure in a panelGroup for easy updating via Ajax. The problem is that these fragments each contain multiple modal dialogs which have fields that should be submitted independently from the outer structure
Is there any technique/ or something in omnifaces that can allow me to exclude specific components from the execute/render process?
rendered attribute allow to exclude component from rendering. Modal dialog(s) can be moved outside form.
I think the answer is no, but the question has been put to me so I'd like to confirm. My understanding is that any custom XBL control that I create for use in Form Builder can have one and only one value. Is this correct?
I have always assumed this because the control name is then used in the data instance as the name of the node which contains the the value.
This question comes from the desire to have reusable components with multiple values, for example, an Address control so that addresses can be recorded consistently and the same set of fields does not need to be added many times. Orbeon does have some support for this in the form of Section Templates but because the control names stay the same in each instance of a Section Template this does not work well with our design.
The best idea I've had is that a custom control which records multiple values could encode all the values into a single text string for example in JSON. Of course, this is not ideal.
Are there any other options?
It is possible for controls to have multiple values. When that happens the values are typically stored in nested elements. I.e. a control could bound to an element <address>, and could create nested elements <street>, <city>,<country>, etc to store the different parts of the address.
In practice, you can look at how this is done in the Image Annotation annotation control (see wpaint.xbl), which creates nested elements <image> and <annotation>, leveraging the xxbl:mirror="true" functionality.
There are lot of materials out there differentiating value attribute and binding attribute in JSF.
I'm interested in how both approaches differ from each other. Given:
public class User {
private String name;
private UICommand link;
// Getters and setters omitted.
}
<h:form>
<h:commandLink binding="#{user.link}" value="#{user.name}" />
</h:form>
It is pretty straight forward what happens when a value attribute is specified. The getter runs to return the name property value of the User bean. The value is printed to HTML output.
But I couldn't understand how binding works. How does the generated HTML maintain a binding with the link property of the User bean?
Below is the relevant part of the generated output after manual beautification and commenting (note that the id j_id_jsp_1847466274_1 was auto-generated and that there are two hidden input widgets).
I'm using Sun's JSF RI, version 1.2.
<form action="/TestJSF/main.jsf" enctype="application/x-www-form-urlencoded"
id="j_id_jsp_1847466274_1" method="post" name="j_id_jsp_1847466274_1">
<input name="j_id_jsp_1847466274_1" type="hidden" value="j_id_jsp_1847466274_1">
Name
<input autocomplete="off" id="javax.faces.ViewState" name="javax.faces.ViewState"
type="hidden" value="-908991273579182886:-7278326187282654551">
</form>
Where is the binding stored here?
How does it work?
When a JSF view (Facelets/JSP file) get built/restored, a JSF component tree will be produced. At that moment, the view build time, all binding attributes are evaluated (along with id attribtues and taghandlers like JSTL). When the JSF component needs to be created before being added to the component tree, JSF will check if the binding attribute returns a precreated component (i.e. non-null) and if so, then use it. If it's not precreated, then JSF will autocreate the component "the usual way" and invoke the setter behind binding attribute with the autocreated component instance as argument.
In effects, it binds a reference of the component instance in the component tree to a scoped variable. This information is in no way visible in the generated HTML representation of the component itself. This information is in no means relevant to the generated HTML output anyway. When the form is submitted and the view is restored, the JSF component tree is just rebuilt from scratch and all binding attributes will just be re-evaluated like described in above paragraph. After the component tree is recreated, JSF will restore the JSF view state into the component tree.
Component instances are request scoped!
Important to know and understand is that the concrete component instances are effectively request scoped. They're newly created on every request and their properties are filled with values from JSF view state during restore view phase. So, if you bind the component to a property of a backing bean, then the backing bean should absolutely not be in a broader scope than the request scope. See also JSF 2.0 specitication chapter 3.1.5:
3.1.5 Component Bindings
...
Component bindings are often used in conjunction with JavaBeans that are dynamically instantiated via the Managed
Bean Creation facility (see Section 5.8.1 “VariableResolver and the Default VariableResolver”). It is strongly
recommend that application developers place managed beans that are pointed at by component binding expressions in
“request” scope. This is because placing it in session or application scope would require thread-safety, since
UIComponent instances depends on running inside of a single thread. There are also potentially negative impacts on
memory management when placing a component binding in “session” scope.
Otherwise, component instances are shared among multiple requests, possibly resulting in "duplicate component ID" errors and "weird" behaviors because validators, converters and listeners declared in the view are re-attached to the existing component instance from previous request(s). The symptoms are clear: they are executed multiple times, one time more with each request within the same scope as the component is been bound to.
And, under heavy load (i.e. when multiple different HTTP requests (threads) access and manipulate the very same component instance at the same time), you may face sooner or later an application crash with e.g. Stuck thread at UIComponent.popComponentFromEL, or Threads stuck at 100% CPU utilization in HashMap during JSF saveState(), or even some "strange" IndexOutOfBoundsException or ConcurrentModificationException coming straight from JSF implementation source code while JSF is busy saving or restoring the view state (i.e. the stack trace indicates saveState() or restoreState() methods and like).
Also, as a single component basically references the rest of the entire component tree via getParent() and getChildren(), when binding a single component to a view or session scoped bean, you're essentially saving the entire JSF component tree in the HTTP session for nothing. This will get really costly in terms of available server memory when you have relatively a lot of components in the view.
Using binding on a bean property is bad practice
Regardless, using binding this way, binding a whole component instance to a bean property, even on a request scoped bean, is in JSF 2.x a rather rare use case and generally not the best practice. It indicates a design smell. You normally declare components in the view side and bind their runtime attributes like value, and perhaps others like styleClass, disabled, rendered, etc, to normal bean properties. Then, you just manipulate exactly that bean property you want instead of grabbing the whole component and calling the setter method associated with the attribute.
In cases when a component needs to be "dynamically built" based on a static model, better is to use view build time tags like JSTL, if necessary in a tag file, instead of createComponent(), new SomeComponent(), getChildren().add() and what not. See also How to refactor snippet of old JSP to some JSF equivalent?
Or, if a component needs to be "dynamically rendered" based on a dynamic model, then just use an iterator component (<ui:repeat>, <h:dataTable>, etc). See also How to dynamically add JSF components.
Composite components is a completely different story. It's completely legit to bind components inside a <cc:implementation> to the backing component (i.e. the component identified by <cc:interface componentType>. See also a.o. Split java.util.Date over two h:inputText fields representing hour and minute with f:convertDateTime and How to implement a dynamic list with a JSF 2.0 Composite Component?
Only use binding in local scope
However, sometimes you'd like to know about the state of a different component from inside a particular component, more than often in use cases related to action/value dependent validation. For that, the binding attribute can be used, but not in combination with a bean property. You can just specify an in the local EL scope unique variable name in the binding attribute like so binding="#{foo}" and the component is during render response elsewhere in the same view directly as UIComponent reference available by #{foo}. Here are several related questions where such a solution is been used in the answer:
Validate input as required only if certain command button is pressed
How to render a component only if another component is not rendered?
JSF 2 dataTable row index without dataModel
Primefaces dependent selectOneMenu and required="true"
Validate a group of fields as required when at least one of them is filled
How to change css class for the inputfield and label when validation fails?
Getting JSF-defined component with Javascript
Use an EL expression to pass a component ID to a composite component in JSF
(and that's only from the last month...)
See also:
How to use component binding in JSF right ? (request-scoped component in session scoped bean)
View scope: java.io.NotSerializableException: javax.faces.component.html.HtmlInputText
Binding attribute causes duplicate component ID found in the view
each JSF component renders itself out to HTML and has complete control over what HTML it produces. There are many tricks that can be used by JSF, and exactly which of those tricks will be used depends on the JSF implementation you are using.
Ensure that every from input has a totaly unique name, so that when the form gets submitted back to to component tree that rendered it, it is easy to tell where each component can read its value form.
The JSF component can generate javascript that submitts back to the serer, the generated javascript knows where each component is bound too, because it was generated by the component.
For things like hlink you can include binding information in the url as query params or as part of the url itself or as matrx parameters. for examples.
http:..../somelink?componentId=123 would allow jsf to look in the component tree to see that link 123 was clicked. or it could e htp:..../jsf;LinkId=123
The easiest way to answer this question is to create a JSF page with only one link, then examine the html output it produces. That way you will know exactly how this happens using the version of JSF that you are using.
I'm pretty new to JSF (Just 1 week old) and developing first component. Component is something like a table which takes a collection as input and renders the contents in a table format. In addition to that renders a "Remove" link at the end of each row.
I created "Composite" component (.xhtml) and ComponentType (a java class with #FacesComponent).
I got the complete table rendering and "Remove" link is displayed in each row. Now trying to add with action that is defined in my class with #FacesComponent.
<a4j:commandLink action="#{cc.removeRow(rowKey)}" value="Remove"/>
In my component (java class) I have this method removeRow(Integer rowKey) defined. But on clicking this "Remove" link the action is not triggered. I have "h:form" also defined in the component.
Any help or pointers is much appreciated.
EDITED: just looked at this question How to implement a dynamic list with a JSF 2.0 Composite Component? and it resembles almost my requirement. Just one thing I'm not sure is what would be the form action when it is rendered and if I click the button in the component, how it would call the method inside its own component bean.
Ok, this is the mistake I was doing.
I'm rendering a custom table using Guava "Table" Collection. This initialization of table happens in "encodeBegin" which was called once. So when I clicked on submit it was trying to re-render the table and it sees everything as null and hence throws NPE.
I now extracted the initialization of table to a separate method and a helper method to retrieve existing table if it's not null or re-initialize from the attributes.
It works now.
We are creating a component and want to mimic the concept behind Designer.GetComponentNames, where as we give can obtain a list of the available components on the form or any form in the uses. We haven't been able to get to the root of GetComponentNames. Any input would be much appreciated.
LE: Actually I take that back. I need this from the design time aspect.
Runtime? You have the Vcl.Forms.TScreen.Forms array for all the displayed forms, and you have Vcl.Forms.Application.Components containing all your forms IIRC. Then, each form has a Components array.
If I understand the first part of your question, you want to get a list of components owned by a form (by name) at designtime.
As background, I have a non-visual component (Call it TColorEdits.) that manages the colors of selected TWinControls on a form at runtime. This component has a TStrings property that contains the names of selected TWinControls on the form. The names of TWinControls to be managed may be selected at designtime using a dialog (dlgEditColors) that contains a couple listboxes, one of which is named DstList and shows all TWinControls available for management by TColorEdits.
So, here is some (simplified) code I use to get the names of TWinControls on a form at designtime and load the TWinControl names into DstList.
{ Load names of TWinControls owned by a form into TListBox DstList }
for i := 0 to TColorEdits(GetComponent(0)).Owner.ComponentCount - 1 do
if ((TColorEdits(GetComponent(0)).Owner.Components[i] is TWinControl) then
dlgEditColors.DstList.Items.Add(TColorEdits(GetComponent(0)).Owner.Components[i].Name);
You should be able to adjust the above code as part of a custom property editor for your component. Hope this helps with the first part of your question.