Spring Boot Mongo findById returns null - spring

Question

I have a collection, with documents having a field named _id of type String, not generated manually.
I have been trying to get a document using its id.
val criteria = Criteria.where("_id").`is`("a2z3e44R")
val document = mongoTemplate.findOne(Query.query(criteria), MyDocument::class.java) // returns null
val criteria = Criteria.where("_id").`is`(ObjectId("a2z3e44R"))
val document = mongoTemplate.findOne(Query.query(criteria), MyDocument::class.java) // returns null
val document = mongoTemplate.findById("a2z3e44R", MyDocument::class.java) // returns null
mongoTemplate.findAll(MyDocument::class.java).first { myDocument ->
myDocument._id == "a2z3e44R"
} // OK...
MyDocument is
data class MyDocument(val _id: String, val name: String)
Trying to find a document by another field works.
An idea of what I could be missing or a workaround?

Answer 1

You should indicate the type of the id like this
public class Article {
#MongoId(value = FieldType.OBJECT_ID)
private String id;
private String title;
private String desc;
}

Answer 2

Try mark _id with annotation #Id. The #Id annotation is used to specify the identifier for Spring.
data class MyDocument(#Id val _id: String, val name: String)

Answer 3

Ypu could define in your repository:
public interface MyDocumentRepository extends MongoRepository<MyDocument, String> {
Pets findBy_id(ObjectId _id);
}
and use it :
myDocumentRepository.findBy_id("a2z3e44R");
for more info see
or
ObjectId objID = new ObjectId("a2z3e44R");
query.addCriteria(Criteria.where("_id").lt(objID));
like this other answer link