Evaluate list contains string in JSTL

Question

I need to hide an element if certain values are present in the JSP   The values are stored in a List so I tried    lt c if test      mylist contains  myValue      gt style  display none   lt  c if gt    But  it doesn t work    How can I evaluate if a list contains a value in JSTL  the list and the values are strings

User · Answer

there is no built-in feature to check that - what you would do is write your own tld function which takes a list and an item, and calls the list's contains() method. e.g.

//in your own WEB-INF/custom-functions.tld file add this
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
        "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib
        xmlns="http://java.sun.com/xml/ns/j2ee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
        version="2.0"
        >
    <tlib-version>1.0</tlib-version>
    <function>
        <name>contains</name>
        <function-class>com.Yourclass</function-class>
        <function-signature>boolean contains(java.util.List,java.lang.Object)
        </function-signature>
    </function>
</taglib>

Then create a class called Yourclass, and add a static method called contains with the above signature. I m sure the implementation of that method is pretty self explanatory:

package com; // just to illustrate how to represent the package in the tld
public class Yourclass {
   public static boolean contains(List list, Object o) {
      return list.contains(o);
   }
}

Then you can use it in your jsp:

<%@ taglib uri="/WEB-INF/custom-functions.tld" prefix="fn" %>
<c:if test="${  fn:contains( mylist, myValue ) }">style='display:none;'</c:if>

The tag can be used from any JSP in the site.

edit: more info regarding the tld file - more info here

User · Answer

lt c if test    fn contains task subscribers  customer    gt    This works fine for me

User · Answer

fn contains  1 2 4 8   2     OR       lt c if test      fn contains theString   test     gt        lt p gt Found test string lt p gt     lt  c if gt      lt c if test      fn contains theString   TEST     gt        lt p gt Found TEST string lt p gt     lt  c if gt

User · Answer

If you are using Spring Framework  you can use Spring TagLib and SpEL    lt    taglib prefix  spring  uri  http   www springframework org tags    gt  ---  lt spring eval var  containsValue  expression  mylist contains myValue     gt   lt c if test    containsValue   gt style  display none   lt  c if gt

User · Answer

If you are using EL 3 0   the best approach in this case is as this other answer explained in another topic      For a Collection it s easy  just use the Colleciton contains     method in EL    lt h panelGroup id  p1  rendered    bean panels contains  p1     gt     lt  h panelGroup gt   lt h panelGroup id  p2  rendered    bean panels contains  p2     gt     lt  h panelGroup gt   lt h panelGroup id  p3  rendered    bean panels contains  p3     gt     lt  h panelGroup gt        For an Object    array   you d need a minimum of EL 3 0 and utilize   its new Lambda support    lt h panelGroup id  p1  rendered    bean panels stream   anyMatch v - gt  v     p1   get     gt     lt  h panelGroup gt   lt h panelGroup id  p2  rendered    bean panels stream   anyMatch v - gt  v     p2   get     gt     lt  h panelGroup gt   lt h panelGroup id  p3  rendered    bean panels stream   anyMatch v - gt  v     p3   get     gt     lt  h panelGroup gt        If you re not on EL 3 0 yet  you d need to create a custom EL   function

User · Answer

You need to use the fn contains   or fn containsIgnoreCase   function    lt    taglib prefix  fn  uri  http   java sun com jsp jstl functions   gt           lt c if test    not fn containsIgnoreCase mylist   apple     gt           lt p gt Doesn t contain  apple  lt  p gt       lt  c if gt    or     lt c if test    not fn contains mylist   Apple     gt               lt p gt Contains  Apple  lt  p gt           lt  c if gt    Note   This will work like mylist toString   contains  apple   and if this is not what you are looking for better use a other approach

User · Answer

Sadly  I think that JSTL doesn t support anything but an iteration through all elements to figure this out   In the past  I ve used the forEach method in the core tag library    lt c set var  contains  value  false    gt   lt c forEach var  item  items    myList   gt     lt c if test    item eq myValue   gt       lt c set var  contains  value  true    gt     lt  c if gt   lt  c forEach gt    After this runs    contains  will be equal to  true  if myList contained myValue

User · Answer

The following is more of a workaround than an answer to your question but it may be what you are looking for   If you can put your values in a map instead of a list  that would solve your problem  Just map your values to a non null value and do this  lt c if test    mymap myValue ne null   gt style  display none   lt  c if gt  or you can even map to style  display none  and simply output   mymap myValue

User · Answer

I found this solution amazing     lt    taglib prefix  c  uri  http   java sun com jsp jstl core    gt    lt    taglib uri  http   java sun com jsp jstl functions  prefix  fn    gt   lt      ArrayList list   new ArrayList       list add  one       list add  two       list add  three      gt   lt c set var  list  value   lt   list  gt     gt   lt html gt   lt body gt          My list is   list  lt br  gt   lt c if test    fn contains list   two     gt          My list contains two  lt br  gt   lt  c if gt   lt c if test    fn contains list         gt          My list contains     lt  c if gt   lt  body gt   lt  html gt     The output for the code above is   My list is  one  two  three   My list contains two  My list contains    I hope it helps someone

User · Answer

Another way of doing this is using a Map  HashMap  with Key  Value pairs representing your object    Map lt Long  Object gt  map   new HashMap lt Long  Object gt     map put new Long 1    one    map put new Long 2    two      In JSTL   lt c if test    not empty map 1    gt    This should return true if the pair exist in the map

[java] Evaluate list.contains string in JSTL

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