public interface Item
功能描述: if you use item in DataRangers, you should define item in DataRangers before using it
example: the item has properties {id,item_name,title,price}
then you should define a class like
class BookItem implements Item{
private String item_id;// =>id
private String item_name;// =>item_name
private String title;
private float price;
}
Note: the id in DataRangers is the same as item_id in sdk