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Evaluate list.contains string in JSTL

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青春惊慌失措
青春惊慌失措 2020-12-07 14:08

I need to hide an element if certain values are present in the JSP

The values are stored in a List so I tried:
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  • 遥遥无期
    2020-12-07 14:51

    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.

    <h:panelGroup id="p1" rendered="#{bean.panels.contains('p1')}">...</h:panelGroup>
<h:panelGroup id="p2" rendered="#{bean.panels.contains('p2')}">...</h:panelGroup>
<h:panelGroup id="p3" rendered="#{bean.panels.contains('p3')}">...</h:panelGroup>

    For an Object[] (array), you'd need a minimum of EL 3.0 and utilize its new Lambda support.

    <h:panelGroup id="p1" rendered="#{bean.panels.stream().anyMatch(v -> v == 'p1').get()}">...</h:panelGroup>
<h:panelGroup id="p2" rendered="#{bean.panels.stream().anyMatch(v -> v == 'p2').get()}">...</h:panelGroup>
<h:panelGroup id="p3" rendered="#{bean.panels.stream().anyMatch(v -> v == 'p3').get()}">...</h:panelGroup>

    If you're not on EL 3.0 yet, you'd need to create a custom EL function. [...]

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  • 暗喜
    2020-12-07 14:53

    You need to use the fn:contains() or fn:containsIgnoreCase() function.

    <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>

    ...

     <c:if test="${not fn:containsIgnoreCase(mylist, 'apple')}">
        <p>Doesn't contain 'apple'</p>
    </c:if>

    or 

    <c:if test="${not fn:contains(mylist, 'Apple')}">
            <p>Contains 'Apple'</p>
        </c:if>

    Note: This will work like mylist.toString().contains("apple") and if this is not what you are looking for better use a other approach.

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  • 南方客
    2020-12-07 14:53

    I found this solution amazing. 

    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> 
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%
   ArrayList list = new ArrayList();
   list.add("one");
   list.add("two");
   list.add("three");
%>
<c:set var="list" value="<%=list%>" />
<html>
<body>
        My list is ${list}<br/>
<c:if test='${fn:contains(list, "two")}'>
        My list contains two <br/>
</c:if>
<c:if test='${fn:contains(list, ",")}'>
        My list contains , 
</c:if>
</body>
</html>

    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.

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  • 猫巷女王i
    2020-12-07 14:57

    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 <c:if test="${mymap.myValue ne null}">style='display:none;'</c:if> or you can even map to style='display:none; and simply output ${mymap.myValue}

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