How to check null and empty condition using Thymeleaf in one single operation?

Question

Is there any way to check both null and empty condition in Thymeleaf?

Approach 1

1) .variable1?.variable2?.variable3
2) variable!=null 
3) variable!=''

If we combine two conditions like (variable!='' And variable!=null) I am having issue when rendering.

I am trying following sample

${#strings.concat(#strings.concat('class ',variable1?.variable2), ' ', variable1?.variable2?.variable3)}

I also used containsKey as well but it is behaving differently.

See `${#strings.isEmpty(variable)}`. It will check for empty or null and call `trim()`. — riddle_me_this, Jul 12 '18 at 15:51
Can you also post what you're trying to do? It seems like you may really want `th:classappend` but I can't readily tell. — riddle_me_this, Jul 12 '18 at 15:53
@vphilipnyc if you've posted your first comment as an answer, you could earn +300 reputation in 18 months. see [proof](https://stackoverflow.com/a/54048650/1429387). — naXa stands with Ukraine, Jul 23 '20 at 13:27
@naxa Lol, maybe you can buy me a beer with all of those points — riddle_me_this, Jul 23 '20 at 17:31
@vphilipnyc ahah! no, problem :) contact me and request your free beer https://t.me/nullgz — naXa stands with Ukraine, Jul 24 '20 at 05:28

score 71 · Answer 1 · answered Jan 05 '19 at 03:12

71

Try ${#strings.isEmpty(variable)}.

From Tutorial | Using Thymeleaf | Strings:

/*
 * Check whether a String is empty (or null). Performs a trim() operation before check
 */
${#strings.isEmpty(name)}

answered Jan 05 '19 at 03:12

naXa stands with Ukraine

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shouldn't it be `${#!string.isEmpty(variable)}` with a **!** in front? – Faraz Apr 03 '19 at 22:30
7

@FarazDurrani it depends on what you need. `${#strings.isEmpty(name)}` is true if `name` is null or empty. `${!#strings.isEmpty(name)}` or `${not #strings.isEmpty(name)}` is true if `name` is not null and not empty. – naXa stands with Ukraine Apr 04 '19 at 05:41
1

Thanks for your time and effort – Ahmed Mahmoud Sep 16 '20 at 12:38
This should be the selected answer. – levacjeep Jul 30 '21 at 17:23
1

also works with ${#arrays.isEmpty(myArray)} – robjwilkins Sep 10 '21 at 10:31

score 21 · Accepted Answer · edited Jan 05 '19 at 02:55

21

In order to check null or empty string using thymeleaf expressions, Use this approach : ---

<div th:if= "${searchResults.results != null}">

OR, this :--

<div th:if= "${searchResults.results != ''}">

Furthermore, you can check the empty or null object on your controller itself and then send the response on your thymeleaf-html page accordingly, like this :--
1.) Your Controller :-

 List ls = //some data from you DAO
    if(ls.isEmpty()){
         model.addAttribute("response","NoData");
      }else{
         model.addAttribute("response",ls);
     }

2.) Then on your Thymleaf page :- - -

<th:block th:if="${response=='NoData'}"> No Data Found </th:block>

PS - I've answered the same question here which helps the questioner hope it helps you as well :-- ThymeLeaf: Not Equal expression in th:if

edited Jan 05 '19 at 02:55

naXa stands with Ukraine

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answered Jul 13 '18 at 13:59

Sumit

917
1
7
18

Hi Sumit I have already tried this .I need both null and empty condition as one single operation rather than as separate condition.I hope u understand what I need – Pradeep Jul 14 '18 at 17:47
For that use **'or'** in between 2 condition , like this :-- **
** Put **""** properly otherwise your page would end up with error.

Sumit

Jul 15 '18 at 05:20

Moreover you can also use **'and'** in a similar way like **or** . Just put **and** in between 2 conditions and it'll work. – Sumit Jul 15 '18 at 05:30

hi Sumit I tried with all these approaches but no luck. Let me try one more time and update you .Thanks for your help – Pradeep Jul 16 '18 at 07:38

**'or' ** And **'and'** operator will definitely work with two conditions in thyemleaf cz I've been using the same approach in my project as well.Hope it works out for you as well. – Sumit Jul 16 '18 at 08:11

score 0 · Answer 3 · answered May 22 '23 at 13:22

0

If you want to print only if NOT a null value or empty sting, then:

 th:if="${not #strings.isEmpty(variableName)}"

answered May 22 '23 at 13:22

Tomas Pinto

121
6

How to check null and empty condition using Thymeleaf in one single operation?

3 Answers3

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