An XML document container reads and parses XML only when it is
accessed. JXPath traverses Containers transparently -
you use the same paths to access objects in containers as you
do to access those objects directly. You can create
XMLDocumentContainers for various XML documents that may or
may not be accessed by XPaths. If they are, they will be automatically
read, parsed and traversed. If they are not - they won't be
read at all.