I wanted to create a custom component and ended up doing few things the wrong way. Some will find these thing obvious, but I belive to some it will be usefull as well.
beforeRenderTemplate / beforeRenderBody
Documentation clearly states that if a component doesn't have body, RenderBody phase is skipped, never the less I used that phase to create a custom component that outputs HTML by it self. What happened is that it worked when I used the component this way:
<t:MyComp source="listData"> </t:MyComp>
but it did not work when the space between tags was removed, or written as single tag
<t:MyComp source="listData"/>
If you don't intend to use the template supplied to your component's body (between tags), the proper place for your code is inside beforeRenderTemplate.
HINT: you can use @BeforeRenderTemplate, @BeforeRenderBody annotations instead method names
non component classes/interfaces in myApp.pages and myApp.components and myApp.base packages
pages and components are instrumented by tapestry, they are also in a separate class loader, and you should avoid using their packages for any non component classes/interfaces. You are most likely to get ClassCastException or CoercionException.
For me these problems were result of trying to make a component as fast as I can. I was eager to use the class reloading feature, and was also lazy to separate an interface to a top level class, so I created an interface for a ListModel in my component and implemented it as inner class of the test page. I was perplexed by the exceptions that were thrown, and at first thought that the cause was in me using generics. At this time I can not in detail explain why these errors occur, but to recommend avoiding this situation.