Many to many relationship using spring boot and mongoDB - mongodb

Question

I am new to spring boot technology.
I have a problem, how to map many to many relationships using spring boot when passed the objectId of another collection and retrieve the details of that object too.
Ex:
There are two models named Vehicles & Categories. When creating a new vehicle type we can pass the Category Id like below.
When retrieving the Vehicle should display like this.
This example developed using node.js and express.js.
Like that way how I can do that for spring boot. I tried with #JoinColumns, #DBRef and none of them doesn't work for me.
Here are my models.
Vehicle model
#Document(collection = "Vehicle")
public class Vehicle {
#Id
private String id;
private String name;
private String type;
private List<Category> categoryList;
//getters and setters go here
Category model
#Document(collection = "Category")
public class Category {
#Id
private String id;
private String name;
private Double amount;
//getters and setters go here
It's better if you can tell me the way of implementing the Controller and Service or Repository according to this.
Thanks in advance.

Answer 1

can't help you with spring-boot stuff but you need to do a $lookup operation to join the foreign documents using the mongodb driver you're using.
the following is how it's done using mongo shell:
db.Vehicle.aggregate(
[
{ $match: { _id: "vehicle-id" } },
{
$lookup: {
from: "Category",
localField: "categories._id",
foreignField: "_id",
as: "categories"
}
}
])
see it in action here: https://mongoplayground.net/p/OgXrAxE2uXu
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