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:

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...)

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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.