Hello all!

My first post here :)
I can say i am new to Java, but my situation i think is more related to Spring Data.

I am working on a project, using MongoDB, and i need to save this kind of structure:

Java Code:
MyObject:{
"_id" : ObjectId( "4fe86664da06e6a3b93bde30" ),
"_class" : "com.data.entity",
"name" : "the name",
"description" : "the description",
"rules": {
		"column1":"value1", 
		"column2":"value2", 
		"column3": {ObjectId(), ObjectId}
	},
}

.....

@Id
private ObjectId id;

private String name;
private String description;
private ?? rules;
I already have my Entity / class with all the getters and setters to create "MyObject" object, but with this new "rule" list in my mongodb collection, i really don't know how to specify it on Java and also how to handle it.
I mean, what type should it have (List, ArrayList) ? and in terms of setters, what would be the best way to store a structure like the "rules" into my object =

Any help will be appreciated!
Please tell me if i wasn't clear enough...

Thank in advance!