code: protected boolean condition() throws JspTagException {
          try {
              Object r = ExpressionEvaluatorManager.evaluate(
                      "test", test, Boolean.class, this, pageContext);
              if (r == null) {
                  throw new NullAttributeException("when", "test");
              } else {
                  return (((Boolean) r).booleanValue());
              }
          } catch (JspException ex) {
              throw new JspTagException(ex.toString(), ex);
          }
      }
docs: Supplied conditional logic