Access Enum value using EL with JSTL

Question

I have an Enum called Status defined as such   public enum Status         VALID  valid    OLD  old         private final String val       Status String val            this val   val             public String getStatus             return val             I would like to access the value of VALID from a JSTL tag  Specifically the test attribute of the  lt c when gt  tag  E g    lt c when test    dp status eq Status VALID  gt    I m not sure if this is possible

User · Answer

Here are two more possibilities  JSP EL 3 0 Constants As long as you are using at least version 3 0 of EL  then you can import constants into your page as follows   lt    page import  quot org example Status quot    gt   lt c when test  quot   dp status eq Status VALID  quot  gt   However  some IDEs don t understand this yet  e g  IntelliJ  so you won t get any warnings if you make a typo  until runtime  This would be my preferred method once it gets proper IDE support  Helper Methods You could just add getters to your enum  public enum Status      VALID  quot valid quot    OLD  quot old quot       private final String val     Status String val        this val   val         public String getStatus         return val         public boolean isValid         return this    VALID         public boolean isOld         return this    OLD         Then in your JSP   lt c when test  quot   dp status valid  quot  gt   This is supported in all IDEs and will also work if you can t use EL 3 0 yet  This is what I do at the moment because it keeps all the logic wrapped up into my enum  Also be careful if it is possible for the variable storing the enum to be null  You would need to check for that first if your code doesn t guarantee that it is not null   lt c when test  quot   not empty db status and dp status valid  quot  gt   I think this method is superior to those where you set an intermediary value in the JSP because you have to do that on each page where you need to use the enum  However  with this solution you only need to declare the getter once

User · Answer

A simple comparison against string works    lt c when test    someModel status     OLD    gt

User · Answer

In Java Class       public class EnumTest        Other property link     private String name                    public enum Status                   ACTIVE NEWLINK  BROADCASTED  PENDING  CLICKED  VERIFIED  AWARDED  INACTIVE  EXPIRED  DELETED BY ADMIN                         private Status statusobj          Getter and Setters     So now POJO and enum obj is created   Now EnumTest you will set in session object using in the servlet or controller class session setAttribute  enumTest   EnumTest     In JSP Page   lt c if test    enumTest statusobj     ACTIVE    gt     TRUE    THEN PROCESS SOME LOGIC

User · Answer

Add a method to the enum like   public String getString         return this name        For example  public enum MyEnum       VALUE 1      VALUE 2      public String getString             return this name              Then you can use    lt c if test    myObject myEnumProperty string eq  VALUE 2    gt     lt  c if gt

User · Answer

If using Spring MVC  the Spring Expression Language  SpEL  can be helpful    lt spring eval expression  dp status    T com example Status  VALID  var  isValid    gt   lt c if test    isValid   gt     isValid  lt  c if gt

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I do not have an answer to the question of Kornel  but I ve a remark about the other script examples  Most of the expression trust implicitly on the toString    but the Enum valueOf   expects a value that comes from matches the Enum name   property  So one should use e g     lt   pageContext setAttribute  Status OLD   Status OLD name       gt       lt c when test    someModel status    Status OLD    gt     lt  c when gt

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When using a MVC framework I put the following in my controller   request setAttribute RequestParameterNamesEnum INBOX ACTION name    RequestParameterNamesEnum INBOX ACTION name       This allows me to use the following in my JSP Page    lt script gt  var url    http   www nowhere com    INBOX ACTION      someValue  lt  script gt    It can also be used in your comparison   lt c when test    someModel action    INBOX ACTION   gt    Which I prefer over putting in a string literal

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So to get my problem fully resolved I needed to do the following    lt   pageContext setAttribute  old   Status OLD     gt    Then I was able to do    lt c when test    someModel status    old    gt     lt  c when gt    which worked as expected

User · Answer

I do it this way when there are many points to use     public enum Status         VALID  valid    OLD  old         private final String val       Status String val            this val   val             public String getStatus             return val             public static void setRequestAttributes HttpServletRequest request            Map lt String String gt  vals   new HashMap lt String String gt             for  Status val   Status values                  vals put val name    val value                     request setAttribute  Status   vals              JSP   lt    page import     Status    gt   lt   Status setRequestAttributes request    gt    lt c when test    dp status eq Status VALID   gt

User · Answer

I generally consider it bad practice to mix java code into jsps tag files  Using  eq  should do the trick     lt c if test    dp Status eq  OLD    gt         lt  c if gt

User · Answer

For this purposes I do the following    lt c set var  abc  gt       lt   Status OLD getStatus    gt   lt  c set gt    lt c if test    someVariable    abc   gt            lt  c if gt    It s looks ugly  but works

User · Answer

A simple comparison against string works    lt c when test    someModel status     OLD    gt

User · Answer

lt    page import  com example Status    gt   1    dp status eq Title VALID getStatus    2    dp status eq Title VALID  3    dp status eq Title VALID toString       Put the import at the top  in JSP page header If you want to work with getStatus method  use  1 If you want to work with the enum element itself  use either  2 or  3 You can use    instead of eq

User · Answer

You have 3 choices here  none of which is perfect    You can use a scriptlet in the test attribute    lt c when test   lt    dp getStatus      Status VALID   gt   gt   This uses the enum  but it also uses a scriptlet  which is not the  right way  in JSP 2 0  But most importantly  this doesn t work when you want to add another condition to the same when using      And this means all the variables you want to test have to be declared in a scriptlet  or kept in request  or session  pageContext variable is not available in  tag files   You can compare against string    lt c when test    dp status     VALID    gt   This looks clean  but you re introducing a string that duplicates the enum value and cannot be validated by the compiler  So if you remove that value from the enum or rename it  you will not see that this part of code is not accessible anymore  You basically have to do a search replace through the code each time  You can add each of the enum values you use into the page context    lt c set var  VALID  value   lt   Status VALID  gt    gt   and then you can do this    lt c when test    dp status    VALID   gt    I prefer the last option  3   even though it also uses a scriptlet  This is because it only uses it when you set the value  Later on you can use it in more complex EL expressions  together with other EL conditions  While in option  1  you cannot use a scriptlet and an EL expression in the test attribute of a single when tag

[java] Access Enum value using EL with JSTL

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