Camel Split aggregator to merge exchanges as List

I am simply trying to split a list of Map instances , process them in a bean and merge them in a list object. So I have made this:

<camel:route>
            <camel:from uri="ref:contactHistoryDbRead"/>
            <camel:split parallelProcessing="true" streaming="true" strategyRef="groupedExchangeAggregationStrategy">
                <camel:simple>${in.body}</camel:simple>
                <camel:bean ref="contactHistoryRequestTransformer" method="transform"/>
            </camel:split>
            <camel:bean ref="contactHistoryService" method="createContactHistory"/>
            <camel:to uri="ref:contactHistoryDbUpdate"/>
        </camel:route>

In the end, it splits the List<Map> object, process them but just after the end of split, when I want to get the whole items as a List, it gives me only one of them.

Is it because of the org.apache.camel.processor.aggregate.GroupedExchangeAggregationStrategy? how can I make this?

Thx