CODEWITHSUNDEEP
jspcollectionsjstlel
Vihung
Vihung

Reputation: 13407

How can I check if a collection contains an item using JSP/EL/JSTL

I am using Java 8, Tomcat 8, with Servlet 3.1.0, JSP 2.0 and JSTL 1.2.

I expected to be able to do the following. However, it does not work.

<c:forEach var="item" items="${itemList}" varStatus="status">
  <tr>
    <td>${status.index + 1}</td>
    <td>${item.itemCode}</td>
    <td>${item.displayName}</td>
    <td>
      <c:choose>
        <c:when test="${user.favourites.contains(item)}">Yes</c:when>
        <c:otherwise>No</c:otherwise>
      </c:choose>
    </td>
  </tr>
</c:forEach>

where user.favourites is a Set of items

Could it be that I do not have the right versions of the dependencies. My POM contains;

  <dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>javax.servlet-api</artifactId>
   <version>3.1.0</version>
   <scope>provided</scope>
  </dependency>

  <dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>jsp-api</artifactId>
   <version>2.0</version>
   <scope>provided</scope>
  </dependency>

  <dependency>
   <groupId>javax.servlet</groupId>
   <artifactId>jstl</artifactId>
   <version>1.2</version>
  </dependency>

servlet-api and jsp-api are provided by Tomcat. Is the version for jstl correct?

Upvotes: 4

Views: 18298

Answers (2)

Vihung
Vihung

Reputation: 13407

It turns out that it does work, but that I had another issue at hand.

My entities (item and user) are coming from Hibernate, from two different DAOs in two different queries, and so the item in the favourites list was a different object to the item in the itemList.

I had not implemented (overridden) the hashCode() and equals() methods in my User and Item classes, and so the Collection.contains() was just looking at object identity not equivalence.

As soon as I implemented hashCode() and equals() methods, it all worked as expected.

The way I found this out was I decided to implement a custom TLD function that invoked the Collection.contains(...) method, and then noticed that even that was returning false.

Upvotes: 4

Vicky
Vicky

Reputation: 889

You can use the contains function provided in JSTL tag library. Kindly find more details @ JSTL fn:contains() Function

This would help you.

Upvotes: -3

Related Questions