Evaluate list.contains string in JSTL

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 tldpublic 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

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:

<c:set var="contains" value="false" /><c:forEach var="item" items="${myList}">  <c:if test="${item eq myValue}">    <c:set var="contains" value="true" />  </c:if></c:forEach>

After this runs, ${contains} will be equal to "true" if myList contained myValue.

Another way of doing this is using a Map (HashMap) with Key, Value pairs representing your object.

Map<Long, Object> map = new HashMap<Long, Object>();map.put(new Long(1), "one");map.put(new Long(2), "two");

In JSTL

<c:if test="${not empty map[1]}">

This should return true if the pair exist in the map