Spring Boot : Error creating bean with name 'jpaMappingContext': java.lang.NullPointerException

Question

My combination of is Spring Boot + Spring Data Jpa + Multiple Databases. I am getting following NullPointer exception when starting the application. Feels like SPring Data with

Answer 1

Spring boot have AutoConfiguration classes enabled by default for the data sources allready on classpath. You should explicitly exclude AutoConfiguration class to disable.

Example :

@EnableAutoConfiguration(exclude = {JndiConnectionFactoryAutoConfiguration.class,DataSourceAutoConfiguration.class,
                                    HibernateJpaAutoConfiguration.class,JpaRepositoriesAutoConfiguration.class,DataSourceTransactionManagerAutoConfiguration.class})
@ComponentScan
public class MyBootApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyBootApplication.class, args);
    }
}

Answer 2

Many thanks to Vishal for the idea. In my case it was generic-less implementation of javax.persistence.AttributeConverter that provoked this exception. Changing class MapConverter implements AttributeConverter<Map, String> { ... } to class MapConverter implements AttributeConverter<Map<String, Object>, String> { ... } really helped.

Answer 3

I faced the mentioned issue with mapping in OnetoOne relationship..

My app had the following OneToOne relationship.

A ||---|| B

B ||---|| C

Since its OnetoOne, I kept entity B primary key same as entity A, using @MapsId as mentioned here 

https://vladmihalcea.com/the-best-way-to-map-a-onetoone-relationship-with-jpa-and-hibernate/

Similarly I kept entity C primary key same as entity B.

I fixed this by changing the relationship like this

A ||---|| B

A ||---|| C

Answer 4

For me this turned out to be due to a custom implementation of org.hibernate.usertype.UserType that I was using for mapping JSON types to Java objects.

In my particular case, it was mapping to a java.util.Map and this change in Spring Data JPA was causing a regression on upgrading to that version.

The fix was to explicitly set generic types for the Map - e.g. Map<String, Object> in my case.