Problem with application with spring-boot-starter-data-mongodb and spring-boot-starter-data-jdbc

I have an synthetic application that runs with a mongodb in the persistence layer with a MongoRepository. I use spring-boot-starter-data-mongodb for this. That works.

Now I want to add another DataSource to connect to a Database with JDBC. I want to use spring-boot-starter-data-jdbc in the same project.

Both solutions work perfectly without the other one

Configuration

pom.xml

        <dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-mongodb</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jdbc</artifactId>
		</dependency>
       <!-- db2 driver -->
		<dependency>
			<groupId>com.ibm.db2.jcc</groupId>
			<artifactId>db2jcc</artifactId>
			<version>db2jcc4</version>
		</dependency>

application.properties

spring.datasource.driver-class-name=com.ibm.db2.jcc.DB2Driver
spring.datasource.url=jdbc:db2://db2host:58440/db
spring.datasource.username=user
spring.datasource.password=thePassword

spring.data.mongodb.host=mongohost

I have two Repositories:

KundeRepository

package com.example.demo.adapter;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.repository.MongoRepository;

public interface KundeRepository  extends MongoRepository<KundeRepository.Kunde, String>{

    Kunde findByName(String name);
     
    public static record Kunde(@Id String id, String name) {
    }

}

package com.example.demo.adapter;

import java.math.BigDecimal;
import java.time.LocalDate;
import java.util.List;

import org.springframework.data.jdbc.repository.query.Query;
import org.springframework.data.relational.core.mapping.Column;
import org.springframework.data.repository.Repository;
import org.springframework.data.repository.query.Param;


public interface KometRepository extends Repository<KometRepository.Abrechnungsdaten, Long> {

        @Query("""
                        SELECT NEID, LIEGID, SALDO
                          FROM THETABLE AS ena
                                WHERE ena.LIEGID = :blubb 
                                                """)
        List<Abrechnungsdaten> abrechnungsdaten(@Param("blubb") Long blubb);


        public static record Abrechnungsdaten(
                        @Column("LIEGID") Long liegid,
                        @Column("NEID") Byte neid,
                        @Column("SALDO") BigDecimal saldo) {
        }

}

package com.example.demo.adapter;

import java.time.LocalDate;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class EvalController {

    @Autowired
    KometRepository kometRepository;
    @Autowired
    KundeRepository kundeRepository;

    @GetMapping("komet")
    public KometRepository.Abrechnungsdaten steuerdaten(){
        return kometRepository.abrechnungsdaten(5675384L);
    }

    
    @GetMapping("mongo")
    public KundeRepository.Kunde bla(){
        var name = "Jens";
        kundeRepository.save(new KundeRepository.Kunde("nne", name));
        return kundeRepository.findByName(null);
    }

    
}

Both Repositories works without the other. However, together I get this Error:

***************************
APPLICATION FAILED TO START
***************************

Description:

Field kometRepository in com.example.demo.adapter.EvalController required a bean of type 'com.example.demo.adapter.KometRepository' that could not be found.

The injection point has the following annotations:
        - @org.springframework.beans.factory.annotation.Autowired(required=true)


Action:

Consider defining a bean of type 'com.example.demo.adapter.KometRepository' in your configuration.

What do I miss?

I made it work by adding the annotation @Table("THETABLE") to the Abrechnungsdaten class. A record should work in the same way.

Anyways, I found the hint in JdbcRepositoriesAutoConfiguration. It only gets active for classes annotated with org.springframework.data.relational.core.mapping.Table.

Spring boot seems to be less strict when you only have a single repository (e.g. the JDBC-repository) in place and then assumes that you want to use that.

On the other hand, when you have multiple options, you need to 'tell' Spring Boot that the entity is based on a relational table.