B.20. Provided Visitors

The SQLStringVisitor is a special visitor that can traverse a tree of language interfaces and output the equivalent JBoss Data Virtualization SQL. This visitor can be used to print language objects for debugging and logging. The SQLStringVisitor does not use the HierarchyVisitor described in the last section; it provides both iteration and processing type functionality in a single custom visitor.

The CollectorVisitor is a handy utility to collect all language objects of a certain type in a tree. Some additional helper methods exist to do common tasks such as retrieving all elements in a tree, retrieving all groups in a tree, and so on.