An aggregation can have multiple parameters, which is why this is returned as an array.
一个聚合可以有多个参数，这就是为什么要以数组的形式返回参数。
2
Provides a join point for multiple input messages that enables message aggregation.
提供多个输入消息的联接点，该联接点支持消息聚合。
3
This scenario involves a combination of the two previously described examples, having an aggregation of data from multiple sources embedded within a batch processing aggregation.