Spring boot MongoDb complex query - spring

Question

I have been learning myself MongoDB implementation in Spring Boot.
However, I came into a problem with complex queries.
I cannot find any right solution for how to implement complex queries to MongoDB from Spring boot.
I am querying the database with MongoRepository interface implementation.
Let's say that I have three collections:
Person - 1 Person can have many Pets.
Pet - 1 Pet can have 1 PetToy and 1 Person who owns him.
PetToy - 1 PetToy can belong to 1 Pet.
POJO classes are bellow
What do I want to achieve?
I want to make a query, which would be returned me a Person, whose Pet has a Toy (PetToy) with the name "Teddy".
I could not have found a way how to do it. Furthermore, is it the best practice to even use such complex queries, or is it better to write more of little ones in MongoDB?
POJOs:
#Document
#Data
#ToString
public class Person {
#Id
private String id;
private String firstname;
private String lastname;
private int age;
#DBRef
private Pet pet;
}
#Document
#Data
#ToString
public class Pet {
#Id
private String id;
private String name;
private int age;
#DBRef
private List<PetToy> toys;
}
#Document
#Data
#ToString
public class PetToy {
#Id
private String id;
private String name;
}
I have tried to use MongoRepositories; however, I was not able to make the complex query.
How can one write such a query to a MongoDB from Spring Boot?
Thank you very much in advance.

Answer 1

If you can use embedded attributes, the class model should be:
#Document
#Data
#Builder
public class Person {
#Id
private String id;
private String firstName;
private String lastName;
private int age;
private List<Pet> pets;
}
#Data
#Builder
public class Pet {
private String name;
private int age;
private List<PetToy> toys;
}
#Data
#Builder
public class PetToy {
private String name;
}
The repository with the method that achieves what you want:
public interface PersonRepository extends MongoRepository<Person, String> {
List<Person> getByPetsToysName(String name);
}
The getByPetsToysName method basically navigate between Person's attributes Person->pets->toys->name. More info here.
An example
#Configuration
#EnableMongoRepositories
public class TestMongo implements CommandLineRunner {
private final PersonRepository repository;
public TestMongo(PersonRepository repository) {
this.repository = repository;
}
#Override
public void run(String... args) throws Exception {
repository.save(Person.builder()
.firstName("John")
.lastName("Doe")
.age(20)
.pets(Stream.of(Pet.builder()
.name("Ursa")
.age(1)
.toys(Stream.of(PetToy.builder()
.name("Teddy")
.build())
.collect(Collectors.toList()))
.build())
.collect(Collectors.toList()))
.build());
repository.save(Person.builder()
.firstName("Phillip")
.lastName("Larson")
.age(21)
.pets(Stream.of(Pet.builder()
.name("Bella")
.age(5)
.toys(Stream.of(PetToy.builder()
.name("Lolo")
.build())
.collect(Collectors.toList()))
.build())
.collect(Collectors.toList()))
.build());
List<Person> persons = repository.getByPetsToysName("Teddy");
System.out.println(persons.size());
List<Person> persons1 = repository.getByPetsToysName("Lolo");
System.out.println(persons1.size());
}
}
Logs:
find using query: { "pets.toys.name" : "Teddy" } fields: Document{{}} for class: class Person in collection: person
If you want more complex queries you can to take a look at the Spring Data MongoDB docs.