Differences between ActiveRecord and Repository when generating JPA entity from a database schema using Spring Roo?

Question

As Spring Roo guide here to do DBRE on a schema, we have the below command to generate the entities and theirs related files.

We there can choose between taking the argument --activerecord or --repository; choosing the later will ignore the first.

My question is what are the differences between the two?

roo> database reverse engineer --schema DbSchemaName --package ~.domain --activeRecord --repository --service --testAutomatically --enableViews --includeTables --excludeTables --includeNonPortableAttributes --disableVersionFields --disableGeneratedIdentifiers

Use the --activeRecord option to create 'Active Record' entities (default if not specified).

Use the --repository option to create Spring Data JPA Repositories for each entity. If specified as true, the --activeRecord option is ignored.

Answer 1

Roo talk about those patterns at http://docs.spring.io/spring-roo/docs/1.3.1.RC1/reference/html/base-layers.html#d4e1932

Active Record Pattern

• The active record pattern is an approach to accessing data in a database. A database table or view is wrapped into a class. Thus, an object instance is tied to a single row in the table.

• Example: persist new instance (create new row):

  Part part = new Part();
  part.name = "Sample part";
  part.price = 123.45;
  part.save();
  

Repository pattern

• A Repository mediates between the domain and data mapping layers, acting like an in-memory domain object collection. Conceptually, a Repository encapsulates the set of objects persisted in a data store and the operations performed over them, providing a more object-oriented view of the persistence layer. Repository also supports the objective of achieving a clean separation and one-way dependency between the domain and data mapping layers.

• Example: persist new instance (create new row):

  Part part = new Part(); 
  part.name = "Sample part"; 
  part.price = 123.45; 
  
  //RepositoryFactorySupport ;
  factory = ...; // Instantiate factory here or similar PartRepository 
  repository = factory.getRepository(PartRepository.class); 
  repository.save(part);