code: private void evaluateExpressions() throws JspException {
          /* 
           * Note: we don't check for type mismatches here; we assume
           * the expression evaluator will return the expected type
           * (by virtue of knowledge we give it about what that type is).
           * A ClassCastException here is truly unexpected, so we let it
           * propagate up.
           */
  
          if (keySpecified) {
              keyAttrValue = (String) ExpressionEvaluatorManager.evaluate(
                      "key", key_, String.class, this, pageContext);
          }
  
          if (bundleSpecified) {
              bundleAttrValue = (LocalizationContext)
                      ExpressionEvaluatorManager.evaluate(
                              "bundle", bundle_, LocalizationContext.class, this,
                              pageContext);
          }
      }
docs: Evaluates expressions as necessary