How do I map "id" property into "id" field in Mongo without @Field annotation?

Question

I have multiple classes with the id field. I would like to store their instances in MongoDB using spring-data-mongodb. I would like to map id property in these classes to id field in Mongo.

So here is what my classes look like:

public class Entity {
    private final String id; // = 42

    ...
}

And here is what I am expecting to be in Mongo collection:

{
    "_id": ObjectId("5fba805dfdaaa760974d45de"),
    "id": "42"
}

By default, spring-mongodb maps id property to _id field in Mongo. I know that the simplest way to avoid this is to put @org.springframework.data.mongodb.core.mapping.Field("id") annotation on id property in a Java class. But I prefer not to use this annotation since I would like to keep my model independent of Mongo, or Spring, or whatever. Which options are possible here?

Here is what I have tried or checked:

1. Registering custom AbstractMongoEventListener in order to modify Mongo documents just before they are written to Mongo, or just after they have been read from Mongo. It does not work for me since custom listener is called only during get and insert operations, but not during the update or upsert operations (see discussion here for details).

2. Providing custom FieldNamingStrategy — it does not work since in the spring-data-mongodb code they use strategy only if field name is not id or _id.

3. Providing custom converter for each of my classes. I believe it should work. But this approach seems to be too complicated since I have many classes with many properties in each of them and I'm not sure I would like to have many converters with boilerplate code inside.

Any help would be appreciated.

Answer 1

Don't you think that id with _id is already confusing?

If you have a strong valid reason to have an id (different than DB one); give it a name .e.g: version_id, old_id, other_services_id ... some meaningful name.

And yes using @Field in your case is the simplest way