es the context necessary to parse an expression.
Specifically, if the expression uses a Jakarta Expression Language function 
(for example <code>${fn:toUpperCase(customer.name)}</code>) or a Jakarta Expression Language 
variable, then <a href="../../jakarta/el/FunctionMapper.html" title="class in jakarta.el"><code>FunctionMapper</code></a> and <a href="../../jakarta/el/VariableMapper.html" title="class in jakarta.el"><code>VariableMapper</code></a>
objects must be available within the <code>ELContext</code>