An Expression that refers to a method on an object.
The {@link ExpressionFactory#createMethodExpression} method
can be used to parse an expression string and return a concrete instance
of MethodExpression that encapsulates the parsed expression.
The {@link FunctionMapper} is used at parse time, not evaluation time,
so one is not needed to evaluate an expression using this class.
However, the {@link ELContext} is needed at evaluation time.
The {@link #getMethodInfo} and {@link #invoke} methods will evaluate the
expression each time they are called. The {@link ELResolver} in the
ELContext is used to resolve the top-level variables and to
determine the behavior of the . and []
operators. For any of the two methods, the {@link ELResolver#getValue}
method is used to resolve all properties up to but excluding the last
one. This provides the base object on which the method
appears. If the base object is null, a
PropertyNotFoundException must be thrown.
At the last resolution,
the final property is then coerced to a String,
which provides the name of the method to be found. A method matching the
name and expected parameters provided at parse time is found and it is
either queried or invoked (depending on the method called on this
MethodExpression).
See the notes about comparison, serialization and immutability in
the {@link Expression} javadocs. | 