Data representation issue on AppEngine Datastore Object

Question

Structure of Data:

• 2-D string array of column length 3.

• Eg. {["One","Two","Three"],["One","Two","Three"],["One","Two","Three"],...}

Datatypes tried & did not work:

• String[][3]
• ArrayList<String[3]>

How this data be represented , if not by above Datatypes ?

Answer 1

If you're using the com.google.appengine.api.datastore API, entity properties must be of one of the datastore native types, or a Collection of values of a datastore native type (or types). A single property value can't represent a two-dimensional list without serialization, nor can multiple values for a single property name (the Collection case).

If you can serialize, then that's a potential answer. If you have requirements for indexing values in your array for queries, then you'll need to describe those to figure out an answer. For example, entries in the array could be separate entities, each with a "first", "second", and "third" property; the main entity has a List of Keys.