Tuesday, November 10, 2009

JSF2 Notes

These are the notes I derived from blogs on JSF 2 :
  • Composite Components
Ed Burn's have a number of articles on developing 'composite components'. CC's are for creating true components that we can attach converters, listeners etc. Previously you could do the similar things with the help of the facelets, which was somewhat limited. Rick Hightower has an excelent series of articles about this, called 'Facelets fits JSF like glove'. Here is what a CC looks like in JSF2 :
displayName="label plus text"
<cc:attribute name="label" required="true" />
<cc:attribute name="id" required="true" />
<cc:attribute name="value" required="true" />
<h:outputLabel id="lbl_#{}" for="#{}"
value="#{cc.attrs.label}" />
<h:inputText id="#{}" value="#{cc.attrs.value}" />
This forms a common element with an inputtext and its label. Apparently there are many tricks to learn here. Its formed of two parts, first is the interface. As far as I can tell this is the UIComponent part. We define valueholders, attributes, actionsources that our CC will respond to. Second part is the implementation. This is like the renderer part. We glue the components together here.
One thing that I didn't like while trying out these was, with the facelets way I could use the CC with panelGrid component and the components forming the CC would be on different grids. This way I could easily align the components. Now on jsf2, CC truely acts like one component and all the sub components fit into the same grid.
  • We can define exception handlers on faces-config.
From Ryan Lubke's blog,
  • There is a javax.faces.PROJECT_STAGE context parameter we can play with which will make our application behave differently in different stages. Like on 'development' stage certain components will be added to the view root automatically like perhaps facestrace. We are able to access it through Application.getProjectStage()
  • There is a new Resource handling architecture. By default resources are searched under (webapp_root)/resource or (webapp_root)/META-INF/resources and there is a EL support to load them from the pages. #{resource['lion.jpg']} will generate a url to a image under these locations I mentioned. Spec also enables that different versions of the same resource be available to application.
  • Components can be annotated with @ResourceDependency annotation and provide the list of resources (css, js, images...) they need inorder to work. These resources might be rendered on different parts of the page with the help of h:body and h:head tags.
  • There is 'View Scope' which as long as the view is not changed. It's accessible using UIViewRoot.getViewMap and #{viewScope} through EL.
  • There is a system event listener api where you could listen to events like 'configuration complete'.
  • Now we have control over request parameters. We can validate convert them if needed.

Looks like JSF2 has more nice stuff in it like the 'View Declaration Language'. Spec it self seems to be the best resource at the moment though.

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