Custom Spring Tag with nested Tags

I want to create a custom spring tag that uses other pre created or custom tags to render the content. My tag extends from AbstractHtmlElementBodyTag and inside the method renderDefaultContent I'm trying to add some other tags like a input tag, error messages, aso. But it doesnt work. if I append markup like <form:input ... /> to the tagWriter, the markup will just be outputed but not rendered. I'm also unable to find the correct way to render the created tag if the tag is created by new InputTag().

How can I do that?

thanks for help