How does a composite component set a property in it's client's backing bean?

Question

I have a composite component with an interface that contains this:

<cc:attribute name="model"
                  shortDescription="Bean that contains Location" >
        <cc:attribute name="location" type="pkg.Location"
                      required="true" />
    </cc:attribute>
</cc:interface>

So I can access the Location object in the markup with #{cc.attrs.model.location}.

I also access that object from the backing bean of the composite component like this:

    FacesContext fc = FacesContext.getCurrentInstance();
    Object obj = fc.getApplication().evaluateExpressionGet(fc, 
            "#{cc.attrs.model.location}", Location.class);

So now my composite component has done its work -- how do I call the setter method on the model from the backing bean? (i.e. model.setLocation(someValue) ?

Answer 1

Use ValueExpression#setValue().

FacesContext facesContext = FacesContext.getCurrentInstance();
ELContext elContext = facesContext.getELContext();
ValueExpression valueExpression = facesContext.getApplication().getExpressionFactory()
    .createValueExpression(elContext, "#{cc.attrs.model.location}", Location.class);

valueExpression.setValue(elContext, newLocation);

The Application#evaluateExpressionGet() by the way calls ValueExpression#getValue() under the covers, exactly as described by its javadoc (if you have ever read it...)

---

Unrelated to the concrete problem, are you aware about the possibility to create backing UIComponent class for the composite component? I bet that this is much easier than fiddling with ValueExpressions this way. You could then just use the inherited getAttributes() method to get the model.

Model model = (Model) getAttributes().get("model);
// ...

You can find an example in our composite component wiki page.

Answer 2

what about the attribute "default" ? It seam that it is not implemented when using the backing component implementation.

xhtml :

<composite:interface>
    <composite:attribute name="test" 
                         type="java.lang.Boolean" 
                         default="#{false}"/>
</composite:interface>
<composite:implementation >
    TEST : #{cc.attrs.test}
</composite:implementation >

Java backing implementation :

 testValue = (Boolean) getAttributes().get("test");

if the test attribute is set in the main xhtml no problem : both xhtml and java backing have the same value. But when not set the default value is only on xhtml : The html contains

TEST : false 

But testValue is null in backing