java - Google App Engine Array List is Not a Supported Property Type -


when try persist 2 dimensional arraylist following error:

java.lang.illegalargumentexception: cng_content: java.util.arraylist not supported property type.

i constructing representation of matrix using 2 array lists , trying persist data store.

    key cngkey = keyfactory.createkey("cng", jsoncng.cngid);     entity cngentity = new entity("cng", cngkey);     cngentity.setproperty("cng_name", jsoncng.cngname);     cngentity.setproperty("cng_type", jsoncng.cngtype);     cngentity.setproperty("cng_content", cng);

in code snippet cng of type:

arraylist<arraylist<string>>

i used

arraylist<hashmap<byte,boolean>>

as type of object. however, found hashmaps not supported gae datastore. further, not intending query on stored object. store , retrieve them.

if not querying, persist them json or other text format. beware of maximum entity size.


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