@Override
    public ValueExpression resolveVariable(String variable) {
        ValueExpression ve = null;
        try {
            if (this.vars != null) {
                // try to resolve against the internal map
                ve = this.vars.get(variable);
            }

            if (ve == null) {
                // look in the wrapped variable mapper
                return this.wrapped.resolveVariable(variable);
            }

            return ve;
        }
        catch (Throwable e) {
            throw new ELException("Could not resolve variable: " + variable, e);
        }
    }
Utility class for wrapping a VariableMapper. Modifications occur to the internal Map instance.
The resolving occurs first against the internal Map instance and then against the wrapped VariableMapper
if the Map doesn't contain the requested ValueExpression.
primefaces-integration-tests/src/main/java/org/primefaces/integrationtests/common/VariableMapperWrapper.java