OGNL expressions are not evaluated in a static environment, as Java programs are. Expressions are not compiled to bytecode at the expression level based on static class reachability. The same expression can have multiple paths through an object graph depending upon the root object specified and the dynamic results of the navigation. Objects that are delegated to handle all of the access to properties of objects, elements of collections, methods of objects, resolution of class names to classes and converting between types are collectively known as OGNL extensions. The following sections delve more deeply into these extensions and provide a roadmap as to how they are used within OGNL to customize the dynamic runtime environment to suit the needs of the embedding program.
