public SimpleSpELRule when(String condition) {
        this.condition = new SimpleSpELCondition(condition, parserContext, beanResolver);
        return this;
    }
Specify the rule's condition as SpEL expression.
@param condition of the rule
@return this rule
manager/api/rest-impl/src/main/java/io/apiman/manager/api/notifications/rules/SimpleSpELRule.java