<T> Method getPrimaryRangeKeyGetter(Class<T> clazz) {
        synchronized (primaryRangeKeyGetterCache) {
            if ( !primaryRangeKeyGetterCache.containsKey(clazz) ) {
                Method rangeKeyMethod = null;
                for ( Method method : getRelevantGetters(clazz) ) {
                    if ( method.getParameterTypes().length == 0
                            && ReflectionUtils.getterOrFieldHasAnnotation(method, DynamoDBRangeKey.class)) {
                        rangeKeyMethod = method;
                        break;
                    }
                }
                primaryRangeKeyGetterCache.put(clazz, rangeKeyMethod);
            }
            return primaryRangeKeyGetterCache.get(clazz);
        }
    }
Returns the annotated {@link DynamoDBRangeKey} getter for the class
given, or null if the class doesn't have one.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBReflector.java