NOT EMPTY or NOT NULL?

[Daniel Gee]

I am uncertain about a JSTL tag that I am using.

From a Struts action, I pass a Collection "logdata" in a request scope to my JSP page. Of course, I stored that Collection in an object" "LogData".

The Collection "logdata" can be a null because if I do not find any records in the database table, I return a null.

Now, I am looking at my JSP page (see the code below). I first set a variable called "logRows" and then test it using "${not empty logRows}". Is it correct?

<c:set var="logRows" value="${requestScope.LogData}" />
 
<c:choose>
<c:when test="${not empty logRows}">
<table>
 .....
</table>
</c:when>
<c :-o	 therwise>
   <td colspan="7" align="center" bgcolor="#f5f5f5">No Failed Log-in So Far.</td>
</c :-o	 therwise>
</c:choose>

[alan do]

you could do both...
${not empty logRows || logRows != null}

[Marc Peabody]

"not empty" also does a null check, making it VERY useful. In fact, I never write null checks in JSTL because I always use "not empty".

So your usage is correct.

[Daniel Gee]

I use the NOT EMPTY to do the testing. But, I got an Internal Server Error 500 problem (The log is shown after my code snippet.) I am unable to see the problem with my <c:when ....> tag.

<c:set var="logRows" value="${requestScope.LogData}" />
 
<c:choose>
<c:when test="${NOT EMPTY logRows}">
  .....
</c:when>
<c:otherwise>
   <td colspan="7" align="center" bgcolor="#f5f5f5">No Failed Log-in So Far.</td>
</c:otherwise>
</c:choose>

Root cause of ServletException.
javax.servlet.jsp.JspTagException: javax.servlet.jsp.JspException: An error occurred while evaluating custom action attribute "test" with value "${NOT EMPTY log
Rows}": Encountered "EMPTY", expected one of ["}", ".", ">", "gt", "<", "lt", "=
=", "eq", "<=", "le", ">=", "ge", "!=", "ne", "[", "+", "-", "*", "/", "div", "%
", "mod", "and", "&&", "or", "||", ":", "("] (null)

[Marc Peabody]

Lowercase, partner.