"IllegalArgumentException: At least one JPA metamodel must be present" - when trying to connect application both to mongo and sql - spring

Question

We have a Spring application that connects with no problems to a MongoDB, with #Autowire and all the rest.
Now we also need the app to connect also to an SQL database.
So we crated an #entity class:
#Entity(name = "SqlCarRecord")
#Table(name = "Cars")
final public class SqlCarRecord {
#Id #GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "name", nullable = false)
private String name;
....
And a #repository interface:
#Repository
public interface SqlCarsRepository extends JpaRepository<SqlCarRecord, Long> {
...
And a #Configuraion class like the example here https://www.petrikainulainen.net/programming/spring-framework/spring-data-jpa-tutorial-part-one-configuration/
And in the applicationContext we added
<jpa:repositories base-package="path.to.interface.package" />
In the pom.xml we already have
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
and we added:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
<version>2.0.0.M3</version>
</dependency>
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>javax.persistence</artifactId>
<version>2.1.0</version>
</dependency>
<!-- DataSource (HikariCP) -->
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>2.6.2</version>
</dependency>
<!-- JPA Provider (Hibernate) -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>5.2.10.Final</version>
</dependency>
<!-- Spring Data JPA -->
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-jpa</artifactId>
<version>1.11.6.RELEASE</version>
</dependency>
<!-- adding this to avoid "java.lang.NoClassDefFoundError: org/w3c/dom/ElementTraversal" -->
<dependency>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
<version>1.4.01</version>
</dependency>
<!-- adding this to avoid "ClassNotFoundException: org.springframework.data.util.CloseableIterator" -->
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-commons</artifactId>
<version>1.13.6.RELEASE</version>
</dependency>
And in the #Service class we added:
....
#Autowired
private SqlCarsRepository carsRepository;
The project is built successfully, but when we try to run it, we get this error:
Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean
with name 'jpaMappingContext': Invocation of init method failed; nested
exception is java.lang.IllegalArgumentException: At least one JPA metamodel
must be present!
Some of the things We tried:
change the different versions of spring in the pom,
we tried to comment some of them,
we tried to change the interface to extend CrudRepository,
tried to add an empty constructor to the entity and some other things
with no luck.
Will appriciate help.
Thanks in advance.

Answer 1

I solved the same error message by changing the #SpringBootApplication annotation to this:
#SpringBootApplication(exclude = {JndiConnectionFactoryAutoConfiguration.class,DataSourceAutoConfiguration.class,
HibernateJpaAutoConfiguration.class,JpaRepositoriesAutoConfiguration.class,DataSourceTransactionManagerAutoConfiguration.class})
If you are using the #EnableAutoConfiguration directly, try this:
#EnableAutoConfiguration(exclude = {JndiConnectionFactoryAutoConfiguration.class,DataSourceAutoConfiguration.class,
HibernateJpaAutoConfiguration.class,JpaRepositoriesAutoConfiguration.class,DataSourceTransactionManagerAutoConfiguration.class})
It seems that the root problem is that the Spring Boot is trying to add something that is already on the classpath.
Most of answer taken from https://stackoverflow.com/a/30597861/7470360