String Concatenation in EL

Question

I would like to concatenate a string within a ternary operator in EL Expression Language    Suppose there is a variable named value  If it s empty  I want to use some default text  Otherwise  I need to append it with some static text      empty value    none    value     enabled     This will not compile however  What would be a correct way to write this  Or is this even possible

User · Answer

If you re already on EL 3 0  Java EE 7  WildFly  Tomcat 8  GlassFish 4  etc   then you could use the new    operator for this    lt c out value    empty value    none    value      enabled      gt    If you re however not on EL 3 0 yet  and the value is a genuine java lang String instance  and thus not e g  java lang Long   then use EL 2 2  Java EE 7  JBoss AS 6 7  Tomcat 7  GlassFish 3  etc  capability of invoking direct methods with arguments  which you then apply on String concat      lt c out value    empty value    none    value concat   enabled       gt    Or if you re even not on EL 2 2 yet  then use JSTL  lt c set gt  to create a new EL variable with the concatenated values just inlined in value    lt c set var  enabled  value    value  enabled    gt   lt c out value    empty value    none    enabled     gt

User · Answer

This answer is obsolete  Technology has moved on  Unless you re working with legacy systems see Joel s answer     There is no string concatenation operator in EL  If you don t need the concatenated string to pass into some other operation  just put these expressions next to each other     value    empty value    none      enabled

User · Answer

it also can be a great idea using concat for EL   MAP   JSON problem like in this example      myMap    concat myid   content

User · Answer

With EL 2 you can do the following      this  concat   is   concat   a   concat   test

User · Answer

1 The   operator  has not effect to that in using EL  2 so this is the way to use that    lt c set var  enabled  value    value  enabled    gt     lt c out value    empty value    none    enabled     gt    is this helpful to You

User · Answer

Mc Dowell s answer is right  I just want to add an improvement if in case you may need to return the variable s value as      empty variable     lt variable is empty gt     variable

User · Answer

Since Expression Language 3 0  it is valid to use    operator for string concatenation      empty value    none    value      enabled       valid as of EL 3 0   Quoting EL 3 0 Specification      String Concatenation Operator        To evaluate   A    B           Coerce A and B to String    Return the concatenated string of A and B

[java] String Concatenation in EL

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