Hash Map key check in JSTL

Question

Need help.I have a hash map which is returned from a spring controller to JSP.Is there a way just to check if a certain key exists irrespective of any value(the value may be null too)

Say, the below hash map is being sent from the controller

HashMap hmap = new HashMap();
hmap.put("COUNTRY", "X");
hmap.put("REGION", null);

If the key REGION exists ( value may be anything including null) then display some section in the jsp.

I am trying to access the key as ${hmap['REGION']}

Thanks in advance.

score 11 · Answer 1 · answered Aug 07 '14 at 08:51

11

try using containsKey:

${hmap.containsKey('REGION')}

answered Aug 07 '14 at 08:51

Vipul Paralikar

1,508
10
22

2

@Amz - In order to invoke the map's containsKey() or containsValue() methods, then you need to ensure that you're running a Servlet 3.0 compatible container like Tomcat 7, Glassfish 3, JBoss AS 6, etc and that your web.xml is declared conform Servlet 3.0. This way you can utilize a new EL 2.2 feature: invoking non-getter methods with arguments. – Vipul Paralikar Aug 07 '14 at 11:19
if you don't have a new version of tomcat you can use the fn:containsKey(map,key) from the functions taglib – EdgeCaseBerg Oct 24 '14 at 17:41
1

@EdgeCaseBerg Eh? fn:containsKey? Never heard of this JSTL function! https://docs.oracle.com/javaee/5/jstl/1.1/docs/tlddocs/fn/tld-summary.html – Geeb Oct 20 '15 at 10:55

score 4 · Answer 2 · answered Aug 07 '14 at 08:28

4

<c:forEach var="entry" items="${hmap }" varStatus="status">        
      <c:if test="${entry.key == 'REGION'}">
        <tr>
           <td>${entry.key}</td>
           <td>${entry.value}</td>
        </tr>
      </c:if>
</c:forEach>

Check this, if this solution works or not ? And post if not working and also post your JSP's jstl code.

answered Aug 07 '14 at 08:28

user3145373 ツ

7,858
6
43
62

Thank you ,I am trying to access the key as ${hmap['REGION']} – Amar Aug 07 '14 at 08:29
`${hmap['REGION']}` should work. How you are `sending the HashMap`, check that `HashMap received on JSP` or not ? – user3145373 ツ Aug 07 '14 at 08:33
2

Why on earth would you use a loop? – user207421 Aug 07 '14 at 08:53
@EJP - I think that OP ll iterate the hashmap and if condition match it ll show data otherwise not. What's strange in that ? On earth still yet does anyone haven'r use loop in jstl ? – user3145373 ツ Aug 07 '14 at 08:55
@user3145373ツ : I have the data of the map in the JSP.I am looking for a check where I am trying to identify if the key exist. – Amar Aug 07 '14 at 10:12
@Amz : ok then there are 2 ways, one is to check like a said or second one is other answer given by the : Vipul Paralikar. – user3145373 ツ Aug 07 '14 at 10:55

score 3 · Answer 3 · answered Apr 07 '15 at 12:10

I know that you want to test for where the value may include null, but there's a solution by using the empty operator that is elegant when one might want to also exclude null values in that it will evaluate to true if the value is null or does not exist.

<c:if test="${not empty hmap['REGION']}">
    <%-- conditional block --%>
</c:if>

Hash Map key check in JSTL

3 Answers3

Linked