How do I show a tree with all kind of different nodes in Vaadin 24?

Question

Earlier versions of Vaadin used to have an actual tree component, like in Vaadin 6 (https://vaadin.com/download/book-of-vaadin/vaadin-6/html/components.tree.html) But the current component set does not have a Tree.

There is TreeGrid, which seems to be more like a table with one level of child nodes that -weirdly enough- have to be of the same Class as the table itself (given it needs to share the addColumns with the toplevel). At least I can't seem to figure out how to make it work with a different class as the child nodes.

And there is a 3rd party add-on (https://vaadin.com/directory/component/tree) but that also seems to support a tree of one class (Departments in the example).

I can of course hack this by using some kind of TreeNode intermediate class. But IMHO If you create a tree that takes domain objects as input, you would expect a renderer-class logic, and support for multiple classes in the same tree.

So suppose I have a domain with cities, streets, buildings, appartements, and rooms, how would I represent that in a 5 level deep tree structure in Vaadin (24+)?

Answer 1

The thinking behind TreeGrid is to let the Java type system help you avoid programming mistakes. You can always opt out from type safety on that level by using Object as the item type (i.e. as TreeGrid<Object>) and handling the differences between different types with instanceof checks in various places.

The other alternative is like you mentioned to make the types explicit by introducing some kind of TreeNode class (or even a class hierarchy). In either case, you typically end up with roughly the same amount of code and it's mostly a subjective question on how you want to structure it.