ModelMapper Spring Data integration

Extension of ModelMapper to automatically map identifiers to aggregate instances using Spring Data repositories to look up aggregate instances.

// Some aggregate plus a repository
class SomeAggregateRoot { }

interface SomeRepository extends CrudRepository<AggregateRoot, UUID> { }

// Some DTO to bind request payloads to
class SomeDTO {
  UUID aggregate;
}

// Some domain object referring to aggregates
class SomeDomainType {
  SomeAggregateRoot aggregate;
}

The AggregateMappingModule will enable mapping SomeDTO to SomeDomainType and vice versa:

• The to-aggregate resolution will convert the incoming identifier to the id type of the aggregate and use the repository to look up the aggregate instance.

• The to-identifier mapping will extract the identifier from the aggregate instance.

The AggregateIdentifierProcessor SPI allows to pre- and post-process the identifier values. For example, UriTemplateIdentifierProcessor allows to easily map the identifiers from and to URIs:

class SomeDTO {
  URI aggregate;
}

@Configuration
class SomeConfiguration {

  @Bean UriTemplateIdentifierProcessor uriProcessor() {
    return new UriTemplateIdentifierProcessor(SomeAggregate.class, "/path/{id}");
  }
}

Given that setup, the following JSON would map aggregate in the DTO to the aggregate in the target instance with the identifier 9ebd9beb-5af6-4c69-9b79-f04b472d1bec extracted and converted into the aggregates identifier type in turn.

{
  "aggregate" : "/path/9ebd9beb-5af6-4c69-9b79-f04b472d1bec"
}

Spring Boot auto-configuration

There’s Spring Boot auto-configuration will register the following beans:

• A ModelMapper instance (unless one is already present) collecting all Module beans declared in the ApplicationContext and registering them with the mapper.

• The AggregateMappingModule if Spring Data is on the classpath and no instance of that is already present in the ApplicationContext. All IdentifierProcessor instances available in the context will be registered. The prepared module instance can be customized by registering AggregateMppingConfigurer beans.