jmolecules-spring

JMolecules Spring integration

This module contains core Spring Framework integration for jMolecules abstractions particularly in the domain model and conversion space.

AssociationResolver

The AssociationResolver is compatible with both jMolecules as well as Spring Data’s CrudRepository. That means that Spring Data repository implementations can simply add AssociationResolver as additional fragment interface and by that expose API to easily resolve Association instances into their target aggregate:

class Order implements AggregateRoot<Order, OrderIdentifier> {
  Association<Customer, CustomerIdentifier> customer;
}

class Customer implements AggregateRoot<Customer, CustomerIdentifier> { /* … */ }

interface Customers extends AssociationResolver<Customer, CustomerIdentifier> { /* … */ }

Customers customers = … // obtain repository
Customer customers.resolveRequired(order.customer); // resolve Association

Converter implementations

The module contains a set of primitive and transitive implementations of Spring’s Converter infrastructure to convert between primitives, Identifier implementations and Associations.

• PrimitivesToIdentifierConverter converts from primitive values to Identifier implementations by expecting a static factory method named of(…) on the identifier type taking the primitive value as argument. By default, both String and UUID are supported for that.

• PrimitivesToAssociationConverter uses the just mentioned one but adds a conversion step using Association.forId(…) to create an Association instance.

Additional converters for the translation back into primitives exist, too.

Base class for JPA AttributeConverter implementations to persist Associations

The AssociationAttributeConverter base class allows easy implementation of JPA AttributeConverter implementations to persist Association instances. If you want to implement them manually, this looks like this:

@Converter
class CustomerAssociationConverter extends AssociationAttributeConverter {

  CustomerAssociationConverter() {
    super(CustomerIdentifier.class);
  }
}

@Entity
class Order {

  @Id OrderIdentifier id;
  @Convert(converter = CustomerAssociationConverter.class)
  Association<Customer, CustomerIdentifier> customer;
}

As you can see, you need to provide a custom sub class of AssociationAttributeConverter to set up the converter with the identifier type it is supposed to work with and annotate the Association field to use that converter implementation. You can avoid all this boilerplate code by using the jMolecules ByteBuddy Plugin that will transparently create such a class based on the type declared in the Association declaration and automatically annotate the entity’s association field to use the generated converter.

Support code to implement for Persistable for MongoDB, JPA and JDBC

The jMolecules ByteBuddy plugin allows to generate implementations of Spring Data’s Persistable for domain types mapped by JPA, JDBC and MongoDB. The necessary infrastructure code (NotNewCallback, MutablePersistable) is contained in this module.