The interface for an expression-language validator and evaluator.
Classes that implement an expression language expose their functionality
via this interface.
The validate() and evaluate() methods must be thread-safe. That is,
multiple threads may call these methods on the same ExpressionEvaluator
object simultaneously. Implementations should synchronize access if
they depend on transient state. Implementations should not, however,
assume that only one object of each ExpressionEvaluator type will be
instantiated; global caching should therefore be static. No release()
mechanism or robust lifecycle is specified, for language-interpreter
pluggability is experimental in EA2.
WARNING: This class supports experimentation for the EA2
release of JSTL; it is not expected to be part of the final RI or
specification. | 