@Override
  public boolean evaluate(Resource resource) {
    Object propertyValue  = resource.getPropertyValue(getPropertyId());
    Object predicateValue = getValue();

    return predicateValue == null ?
        propertyValue == null :
        propertyValue != null && compareValueTo(propertyValue) == 0;
  }
Predicate that checks equality of a given value to a {@link Resource} property.
ambari-server/src/main/java/org/apache/ambari/server/controller/predicate/EqualsPredicate.java