| Summary: | empty operator doesn't work with java.util.Set instances | ||
|---|---|---|---|
| Product: | Taglibs | Reporter: | Willis Boyce <wboyce> |
| Component: | Standard Taglib | Assignee: | Tomcat Developers Mailing List <dev> |
| Status: | RESOLVED INVALID | ||
| Severity: | normal | ||
| Priority: | P3 | ||
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Hardware: | All | ||
| OS: | All | ||
Submitted by Michael Santos: ---- Regarding this bug: That's the expected behaviour in JSTL 1.0, according to the spec. I don't have a bugzilla user and I am not a committer, so, I am unable to help this user more. Reference: http://weblogs.java.net/pub/wlg/730 Regards, Michael Nascimento Santos ---- In your bug report, you didn't specify which version of JSTL you are using. If you are using JSTL 1.0 then this is the expected behavior. If you look at section A.3.8 of the JSTL 1.0 specification you will find the empty operator defined as follows: empty A is evaluated as follows: ■ If A is null, return true, ■ Otherwise, if A is the empty string, then return true. ■ Otherwise, if A isan empty array, then return true. ■ Otherwise, if A is an empty Map, return true ■ Otherwise, if A is an empty List, return true, ■ Otherwise return false. With JSTL 1.1 the EL was moved to the JSP 2.0 specification domain. With JSTL 1.1 it is now up to the domain of the JSP container to support the JSP 2.0 EL implementation. In JSP 2.0 the empty operator behavior has changed slightly. In JSP 2.0 section JSP.2.3.7, the empty operator behaves as follows: • If A is null, return true, • Otherwise, if A is the empty string, then return true. • Otherwise, if A is an empty array, then return true. • Otherwise, if A is an empty Map, return true, • Otherwise, if A is an empty Collection, return true, • Otherwise return false. Moving to JSTL 1.1 and a JSP 2.0 container will address your problem. |
${empty someSet} will return false if someSet is an instance of java.util.Set, even if it is, in fact, empty. This is because EmptyOperator.java checks for an empty Map and an empty List but not an empty Collection. All that needs to be done is to replace List with Collection, as a List is, of course, a Collection.