How can i check if an attribute is set (not null and not an empty string) with jstl?

Question

E.g.

<c:if test="${post}">
    <h3>${post.title}</h3>  
</c:if>

although if `title` does not exist (ie. the property does not belong to this variable/bean), you want to catch the `javax.el.PropertyNotFoundException` , see question `Checking attribute exists in JSP` on http://stackoverflow.com/questions/2522562/checking-attribute-exists-in-jsp — Adriano, Oct 01 '14 at 08:24
Your question should probably be reformulated as "check if an attribute is **set**" (not null and not an empty string) — Adriano, Oct 01 '14 at 08:31

score 108 · Accepted Answer · answered May 15 '09 at 09:18

108

Use the empty keyword

<c:if test="${not empty post}">
   <h3>${post.title}</h3>   
</c:if>

answered May 15 '09 at 09:18

krosenvold

2

This is definitely the best way. I believe it also checks for `null`. – Alex May 15 '09 at 09:31
1

This is misleading. If the attribute is a list, it is set and is empty, this conditional would return true. – stepanian Oct 07 '17 at 20:15

hejiaming007 · Answer 2 · 2016-10-12T06:15:40.647

12

You can also use '!' instead 'not' :

<c:if test="${!empty post}">
    <h3>${post.title}</h3>
</c:if>

edited Oct 12 '16 at 06:15

answered Aug 10 '13 at 02:36

hejiaming007

2 Answers2