HazelcastSerializationException: Failed to serialize Interface-based Projections

Question

I want to cache result of Interface-based Projections but I got this error

Caused by: com.hazelcast.nio.serialization.HazelcastSerializationException: Failed to serialize 'java.util.ArrayList'

@Repository
    public interface CustomerRepository extends JpaRepository<CustomerRepository, Long> {       
        @Cacheable(value = "customer")
        @Query("select c.first_name as firstName from customer where customer_id in :customerId")
        List<NamesOnly> findByCustomerId( @Param("customerId") List<String> customerId);
    }

    public interface NamesOnly extends Serializable {

        String getCustomerFirstName();

    }

it seems extends Serializable not working

Answer 1

This is a Spring issue, buried in the depths is this:

java.io.NotSerializableException: org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor

Might be another occurrance of this

As a workaround, you could change

List<NamesOnly> findByCustomerId( @Param("customerId") List<String> customerId);

to

List<String> findByCustomerId( @Param("customerId") List<String> customerId);

as your projection only returns a single column, firstName , which presumably is a string.

Without @Cacheable what you get back is a list ( serializable ) of proxy classes ( not serializable ). With @Cacheable the list gets sent to the distributed store (Hazelcast) for caching, and this fails as the list is serializable but the list elements aren't.