Question

Is there a way to call java.util.Map.contains() method in JSP where the Map is a property of a bean.

Answer 1

${fooBean.fooMap.containsValue("baz")}

The above will work in JSP 2.2 or better. If you’re using a pre-JSP 2.2 container (e.g. Java EE 5) then an EL function is probably the better solution.

Static Java method:

package contains;
import java.util.Map;
public class Maps {
    public static boolean containsValue(Map<?, ?> map, Object value) {
        return map.containsValue(value);
    }
}

The file WEB-INF/tlds/maps.tld:

<?xml version="1.0" encoding="UTF-8"?>
<taglib version="2.1"
  xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd">
  <tlib-version>1.0</tlib-version>
  <short-name>maps</short-name>
  <uri>/WEB-INF/tlds/maps</uri>
   <function>
    <description>Returns true if the value is contained</description>
    <name>containsValue</name>
    <function-class>contains.Maps</function-class>
    <function-signature>
      boolean containsValue(java.util.Map, java.lang.Object)
    </function-signature>
  </function>
</taglib>

Usage:

<%@taglib prefix="maps" uri="/WEB-INF/tlds/maps" %>
...
${maps:containsValue(fooBean.fooMap, "baz")}