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.
           */
  
          xml = ExpressionUtil.evalNotNull(
                  "transform", "xml", xml_, Object.class, this, pageContext);
          xmlSystemId = (String) ExpressionUtil.evalNotNull(
                  "transform", "xmlSystemId", xmlSystemId_, String.class,
                  this, pageContext);
          xslt = ExpressionUtil.evalNotNull(
                  "transform", "xslt", xslt_, Object.class, this,
                  pageContext);
          xsltSystemId = (String) ExpressionUtil.evalNotNull(
                  "transform", "xsltSystemId", xsltSystemId_, String.class,
                  this, pageContext);
          result = (Result) ExpressionUtil.evalNotNull(
                  "transform", "result", result_, Result.class, this, pageContext);
  
      }
docs: /* Evaluates expressions as necessary