Spring Data Mongodb - repository for collection with different types

Question

I have a mongo collection that may contain three types of entities that I map to java types:

• Node
• LeafType1
• LeafType2

Collecti

Answer 1

If Node\LeafType1\LeafType2 are sub-classes of AbstractMyCollectionNode, then things will be easy. Just declare the repository like you write:

public interface MyCollectionRepository extends MongoRepository { }

We have done this in a project, and it works good. Spring Data will add an property named '_class' to the documents in mongodb collection, so that it can finger out which class to instantiate.

Documents that stored in one collection may have some similarity, maybe you can extract a generic class for them.

Here are some code copied from one of our projects:

Entity:

public abstract class Document {
    private String id;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
    ....

---

public class WebClipDocument extends Document {
    private String digest;
    ...

Repository:

public interface DocumentDao extends MongoRepository{
...

And, if your documents in mongodb collection does not have the "_class" property. You can use Converter:

When storing and querying your objects it is convenient to have a MongoConverter instance handle the mapping of all Java types to DBObjects. However, sometimes you may want the `MongoConverter’s do most of the work but allow you to selectively handle the conversion for a particular type or to optimize performance.