Mapping a document with partly-defined schema

问题

I'm writing a demo app using Spring & MongoDB as a database.

My main domain class looks like:

@Document
public class Person {

    @Id
    private String id;

    //Some other fields
    private DBObject additionalData;

}

The key is that additionalData is a subdocument with no schema specified, it is kind of user-defined JSON. But when I am parsing this json (using (DBObject) JSON.parse(value) expression), it is stored as a string in MongoDB, and I need it to be a nested document structure.

Searched for couple of hours, found no solution. Any ideas?

回答1:

I'm not really sure of the expected result of casting the result of

JSON.parse(value)

to DBObject, which is an interface, not a class. Try casting the result to an implementation of DBObject BasicDBObject (or BasicDBList), or a Map<String, Object> as mentioned in the comments (it is also an interface, but it does work).

If you're working with Spring Data Rest, you will probably not need to deserialize "manually", Spring will do it for you. Check this answer for a basic example of what to do. Having data with no schema specified may not be the best idea around (mongodb saves you from doing it at the database level, but you should do it at the application level), but I use similar tricks in production, and you can somehow make it work.

来源：https://stackoverflow.com/questions/36406195/mapping-a-document-with-partly-defined-schema