Configure Spring Boot with two DataSources

I am using Spring Boot 2.X with Hibernate 5.X to connect two MySQL databases (Bar and Foo). I want to be able to list the different entities, with all their attributes (ID, Name and relationships @OneToMany/@ManyToOne ), of each of the two databases from an @RESTController.

I can make the list for the database that I have marked as @Primary (in this case Foo), however, when I try to do the same list for the other database (Bar) I always get an exception when returning the @OneToMany attribute (declared as lazy). If I write the second database (Bar) as @Primary instead of Foo, I get the opposite effect. Is there a way to solve this by keeping the data like Lazy?

This is the exception I'm getting:

...w.s.m.s.DefaultHandlerExceptionResolver :
Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: 
    Could not write JSON document: failed to lazily initialize a collection of role: 
        com.foobar.bar.domain.Bar.manyBars, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]-com.foobar.bar.domain.Bar["manyBars"]); 
    nested exception is com.fasterxml.jackson.databind.JsonMappingException:
        failed to lazily initialize a collection of role: 
        com.foobar.bar.domain.Bar.manyBars, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]->com.foobar.bar.domain.Bar["manyBars"])

The configuration of the Foo database:

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactory",
        transactionManagerRef = "transactionManager",
        basePackages = {"com.foobar.foo.repo"})
public class FooDbConfig {

    @Primary
    @Bean(name = "dataSource")
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Primary
    @Bean(name = "entityManagerFactory")
    public LocalContainerEntityManagerFactoryBean entityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("dataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages("com.foobar.foo.domain")
                .persistenceUnit("foo")
                .build();
    }

    @Primary
    @Bean(name = "transactionManager")
    public PlatformTransactionManager transactionManager(
            @Qualifier("entityManagerFactory") EntityManagerFactory entityManagerFactory) {
        return new JpaTransactionManager(entityManagerFactory);
    }
}

The configuration of the Bar database:

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "barEntityManagerFactory",
        transactionManagerRef = "barTransactionManager", basePackages = {"com.foobar.bar.repo"})
public class BarDbConfig {

    @Bean(name = "barDataSource")
    @ConfigurationProperties(prefix = "bar.datasource")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "barEntityManagerFactory")
    public LocalContainerEntityManagerFactoryBean barEntityManagerFactory(
            EntityManagerFactoryBuilder builder, @Qualifier("barDataSource") DataSource dataSource) {
        return builder
                .dataSource(dataSource)
                .packages("com.foobar.bar.domain")
                .persistenceUnit("bar")
                .build();
    }

    @Bean(name = "barTransactionManager")
    public PlatformTransactionManager barTransactionManager(
            @Qualifier("barEntityManagerFactory") EntityManagerFactory barEntityManagerFactory) {
        return new JpaTransactionManager(barEntityManagerFactory);
    }
}

This is the REST driver:

@RestController
public class FooBarController {

    private final FooRepository fooRepo;
    private final BarRepository barRepo;

    @Autowired
    FooBarController(FooRepository fooRepo, BarRepository barRepo) {
        this.fooRepo = fooRepo;
        this.barRepo = barRepo;
    }

    @RequestMapping("/foo")
    public List<Foo> listFoo() {
        return fooRepo.findAll();
    }

    @RequestMapping("/bar")
    public List<Bar> listBar() {
        return barRepo.findAll();
    }

    @RequestMapping("/foobar/{id}")
    public String fooBar(@PathVariable("id") Integer id) {
        Foo foo = fooRepo.findById(id);
        Bar bar = barRepo.findById(id);

        return foo.getName() + " " + bar.getName() + "!";
    }

}

Repositories:

@Repository
public interface FooRepository extends JpaRepository<Foo, Long> {
  Foo findById(Integer id);
}

@Repository
public interface BarRepository extends JpaRepository<Bar, Long> {
  Bar findById(Integer id);
}

Entities for database @Primaria . The entities of the secondary database are equivalent (changing the name of the classes):

@Entity
@Table(name = "foo")
public class Foo {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;

    @Column(name = "name")
    private String name;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "foo")
    @JsonIgnoreProperties({"foo"})
    private Set<ManyFoo> manyFoos = new HashSet<>(0);

    // Constructors, Getters, Setters
}

@Entity
@Table(name = "many_foo")
public class ManyFoo {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;

    @Column(name = "name")
    private String name;

    @ManyToOne(fetch = FetchType.LAZY)
    @JsonIgnoreProperties({"manyFoos"})
    private Foo foo;

    // Constructors, Getters, Setters
}  

Finally, the main method:

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Thank you!