How to do if-else in Thymeleaf

Question

What s the best way to do a simple if-else in Thymeleaf   I want to achieve in Thymeleaf the same effect as   lt c choose gt     lt c when test    potentially complex expression   gt        lt h2 gt Hello  lt  h2 gt     lt  c when gt     lt c otherwise gt        lt span class  xxx  gt Something else lt  span gt     lt  c otherwise gt   lt  c choose gt    in JSTL   What I ve figured so far    lt div th with  condition   potentially complex expression   th remove  tag  gt       lt h2 th if    condition   gt Hello  lt  h2 gt       lt span th unless    condition   class  xxx  gt Something else lt  span gt   lt  div gt    I don t want to evaluate potentially complex expression twice  That s why I introduced local variable condition  Still I don t like using both th if    condition  and th unless    condition     An important thing is that I use two different HTML tags  let s say h2 and span   Can you suggest a better way to achieve it

User · Answer

Another solution is just using not to get the opposite negation    lt h2 th if    potentially complex expression   gt Hello  lt  h2 gt   lt span class  xxx  th if    not potentially complex expression   gt Something else lt  span gt    As explained in the documentation  it s the same thing as using th unless  As other answers have explained      Also  th if has an inverse attribute  th unless  which we could have   used in the previous example instead of using a not inside the OGNL   expression   Using not also works  but IMHO it is more readable to use th unless instead of negating the condition with not

User · Answer

Thymeleaf has an equivalent to  lt c choose gt  and  lt c when gt   the th switch and th case attributes introduced in Thymeleaf 2 0   They work as you d expect  using   for the default case    lt div th switch    user role   gt      lt p th case   admin   gt User is an administrator lt  p gt     lt p th case    roles manager   gt User is a manager lt  p gt     lt p th case     gt User is some other thing lt  p gt    lt  div gt    See this for a quick explanation of syntax  or the Thymeleaf tutorials    Disclaimer  As required by StackOverflow rules  I m the author of Thymeleaf

User · Answer

I tried this code to find out if a customer is logged in or anonymous  I did using the th if and th unless conditional expressions  Pretty simple way to do it    lt  -- IF CUSTOMER IS ANONYMOUS -- gt   lt div th if    customer anonymous   gt      lt div gt Welcome  Guest lt  div gt   lt  div gt   lt  -- ELSE -- gt   lt div th unless    customer anonymous   gt      lt div th text    Hi       customer name   gt Hi  User lt  div gt   lt  div gt

User · Answer

Use th switch as an if-else   lt span th switch    isThisTrue   gt     lt i th case  true  class  fas fa-check green-text  gt  lt  i gt     lt i th case  false  class  fas fa-times red-text  gt  lt  i gt   lt  span gt    Use th switch as a switch   lt span th switch    fruit   gt     lt i th case  Apple  class  fas fa-check red-text  gt  lt  i gt     lt i th case  Orange  class  fas fa-times orange-text  gt  lt  i gt     lt i th case     class  fas fa-times yellow-text  gt  lt  i gt   lt  span gt

User · Answer

Another solution - you can use local variable    lt div th with  expr result     potentially complex expression   gt       lt div th if    expr result   gt           lt h2 gt Hello  lt  h2 gt       lt  div gt       lt div th unless    expr result   gt           lt span class  xxx  gt Something else lt  span gt       lt  div gt   lt  div gt    More about local variables  http   www thymeleaf org doc tutorials 2 1 usingthymeleaf html local-variables

User · Answer

This work for me when I wanted to show a photo depending on the gender of the user   lt img th src  quot   generou    Femenino       images user mujer jpg      images user jpg  quot   alt  quot AdminLTE Logo quot  class  quot brand-image img-circle elevation-3 quot  gt

User · Answer

lt div style  width 100   gt   lt span th each  i      numbers sequence 1  3    gt   lt span th if    i    curpage   gt   lt a href   listEmployee   i   class  btn btn-success custom-width  th text    i   gt  lt  a  lt  span gt   lt span th unless    i    curpage   gt   lt a href   listEmployee   i   class  btn btn-danger custom-width  th text    i   gt  lt  a gt    lt  span gt   lt  span gt   lt  div gt    enter image description here

User · Answer

You can use   If-then-else    if     then     else    Example    User is of type        user isAdmin       Administrator       user type      Unknown      It could be useful for the new people asking the same question

User · Answer

lt div th switch    user role   gt    lt p th case   admin   gt User is an administrator lt  p gt   lt p th case    roles manager   gt User is a manager lt  p gt   lt p th case     gt User is some other thing lt  p gt    lt  div gt     lt div th with  condition   potentially complex expression   th remove  tag  gt   lt h2 th if    condition   gt Hello  lt  h2 gt   lt span th unless    condition   class  xxx  gt Something else lt  span gt   lt  div gt

User · Answer

I d like to share my example related to security in addition to Daniel Fern  ndez    lt div th switch     authentication      authorization expression  isAuthenticated          false   gt       lt span th case    false   gt User is not logged in lt  span gt       lt span th case    true   gt Logged in user lt  span gt       lt span th case     gt Should never happen  but who knows    lt  span gt   lt  div gt    Here is complex expression with mixed  authentication  and  authorization  utility objects  which produces  true false  result for thymeleaf template code   The  authentication  and  authorization  utility objects came from thymeleaf extras springsecurity3 library  When  authentication  object is not available OR authorization expression  isAuthenticated     evaluates to  false   expression returns   false   otherwise   true

User · Answer

In simpler case  when html tags is the same     lt h2 th text    potentially complex expression     Hello     Something else   gt  h2 gt

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