How to use Mongo with Spring Data without ObjectId

Question

I have an existing mongo database in which ids (_id) are persisted as plain Strings.. This is sample data in Mongo DB:

{
    "_id" : "528bb0e2e4b0442f1479f1b4",
    "schoolId" : "URDLKYLFJXLWJGR193778316742298",
    "surname" : "Lewis",
    "admissionNumber" : "0347",
    "firstName" : "Martins"
}

I have a Java object which is of the form:

public class Student {

@Id
private String id;
private String schoolId;
private String surname;
private String admissionNumber;
private String firstName;
}

With Getters and Setters

I also have a repository:

public interface StudentRepository extends MongoRepository<Student, String> {

    Student findOneBySurname(String surname);
    Student findOneById(String id);
    Student findOneBySurnameAndFirstName(String surname, String firstName);
}

When I do a studentRepository.findAll() I am able to get all the Students in the database with all their fields populated correctly.

When I do a studentRepository.findOne("528bb0e2e4b0442f1479f1b4") or a studentRepository.findOneById)"528bb0e2e4b0442f1479f1b4") it returns null

When I do a debug of the mongo query I can see that it is calling:

2015-11-19 16:06:32.327 DEBUG 87081 --- [           main] o.s.data.mongodb.core.MongoTemplate      : findOne using query: { "id" : "528bb0e2e4b0442f1479f1b4"} fields: null for class: class com.ad.josh.domain.Student in collection: Student
    2015-11-19 16:06:32.331 DEBUG 87081 --- [           main] o.s.data.mongodb.core.MongoDbUtils       : Getting Mongo Database name=[joshdb]
    2015-11-19 16:06:32.333 DEBUG 87081 --- [           main] o.s.data.mongodb.core.MongoTemplate      : findOne using query: { "_id" : { "$oid" : "528bb0e2e4b0442f1479f1b4"}} in db.collection: josh.Student

Typically I can see that it is still querying with Object Id and not a plain String.

I have seen suggestions to:

Create a Converter which throws a RuntimeException

But this does not work; it just throws a RuntimeException.

Any suggestions on how to use Spring Data to access a Mongo database where the Ids are defined as String already (in an existing database) would be really appreciated.

Answer 1

I think the problem here is a wrong "_id" format and that is why Mongo cannot recognize any object with such id. It should looks like ObjectId("528bb0e2e4b0442f1479f1b4"), not plain String type.

        {
            "_id" : ObjectId("528bb0e2e4b0442f1479f1b4"),
            "schoolId" : "URDLKYLFJXLWJGR193778316742298",
            "surname" : "Lewis",
            "admissionNumber" : "0347",
            "firstName" : "Martins"
        }

So if you have imported .json with existing data to mongo you need to change id:

"_id": {$oid:"528bb0e2e4b0442f1479f1b4"},

And it should be converted to correct format.

Hope it can help someone.