How to use if-else option in JSTL

Question

Is there an if-else tag available in JSTL

User · Answer

There is no if-else  just if    lt c if test    user age ge 40   gt   You are over the hill   lt  c if gt    Optionally you can use choose-when    lt c choose gt     lt c when test    a boolean expr   gt      do something    lt  c when gt     lt c when test    another boolean expr   gt      do something else    lt  c when gt     lt c otherwise gt      do this when nothing else is true    lt  c otherwise gt   lt  c choose gt

User · Answer

you have to use this code   with  lt    taglib prefix  c  uri  http   www springframework org tags form   gt   and   lt c select gt               lt option value  RCV                    records 0  getDirection       RCV     selected  true         gt                   lt spring message code  dropdown Incoming  text  dropdown Incoming    gt               lt  option gt               lt option value  SND                    records 0  getDirection       SND    selected  true         gt                   lt spring message code  dropdown Outgoing  text  dropdown Outgoing    gt               lt  option gt           lt  c select gt

User · Answer

Besides the need to have an else  in many cases you will need to use the same condition on multiple locations  I prefer to extract the condition into a variable   lt c set var  quot conditionVar quot  value  quot   expression  quot   gt   And after that  you can use the condition variable as many times as you need it       lt c if test  quot   conditionVar  quot  gt              lt  c if gt   lt c if test  quot    conditionVar  quot  gt              lt  c if gt       lt c if test  quot   conditionVar  quot  gt              lt  c if gt   lt c if test  quot    conditionVar  quot  gt              lt  c if gt       The c choose element is good for more complicated situations  but if you need an if else only  I think this approach is better  It is efficient and has the following benefits   more readable if the variable name is well chosen more reusable because the condition is extracted and the resulting variable can be reused for other ifs and in other expressions  It discourages writing the same condition  and evaluating it  multiple times

User · Answer

Yes  but it s clunky as hell  e g    lt c choose gt     lt c when test    condition1   gt             lt  c when gt     lt c when test    condition2   gt             lt  c when gt     lt c otherwise gt             lt  c otherwise gt   lt  c choose gt

User · Answer

In addition with skaffman answer  simple if-else you can use ternary operator like this   lt c set value  34  var  num   gt   lt c out value    num   2 eq 0    even    odd     gt

User · Answer

This is good and efficient approach as per time complexity prospect  Once it will get a true condition   it will not check any other after this  In multiple If   it will check each and condition       lt c choose gt         lt c when test    condtion1   gt          do something condtion1        lt  c when gt         lt c when test    condtion2   gt          do something condtion2        lt  c when gt                                                                lt c when test    condtionN   gt          do something condtionn N        lt  c when gt           lt c otherwise gt          do this w        lt  c otherwise gt       lt  c choose gt

User · Answer

I got away with simply using two if tags  thought I d add an answer in case it s of use to anyone else    lt c if test    condition   gt         lt  c if gt   lt c if test     condition   gt         lt  c if gt    whilst technically not an if-else per se  the behaviour is the same and avoids the clunky approach of using the choose tag  so depending on how complex your requirement is this might be preferable

[jsp] How to use if-else option in JSTL

Examples related to jsp

Examples related to jstl