具有不同类型的Google App Engine数据存储区实体属性

Question

How do I create a property that can accept both a ArrayList<Integer> and ArrayList<String> ?

I tried setting it as ArrayList<Object> but it doesn't accept either parameters.

Answer 1

You can use a Low-level Datastore API to set the same property to either ArrayList<Integer> (which will be stored and retrieved as ArrayList<Long> , by the way) or ArrayList<String> . You should remember, however, to type-check when you retrieve the value of this property (casting from ArrayList<Long> to ArrayList<String> or vice versa is not possible), and you will have to write this code yourself.

In general, this is not a good practice. Strong typing is an advantage of Java. Use it.