@Override
    public VariableResolver getVariableResolver(String name) {
        VariableResolver vr = variableResolvers.get(name);
        return vr != null ? vr : (nextFactory == null ? null : nextFactory.getVariableResolver(name));
    }
@see org.mvel2.integration.impl.BaseVariableResolverFactory#getVariableResolver(java.lang.String)
test/common/src/main/java/io/apiman/test/common/util/TestVariableResolverFactory.java