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spring_conventions.md

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Spring DHIS2 conventions

Bean definitions

Spring Beans are normal classes annotated with one of the standard Spring stereotype annotations:

  • @Repository
  • @Service
  • @Component

Repository

The @Repository stereotype is used to indicate that the class provides the mechanism for storage, retrieval, search, update and delete operation on objects. DHIS2 *Store classes are annotated with @Repository.

@Service

The @Service annotation indicates that the class is responsible for some kind of business logic. DHIS2 *Service classes are annotated with @Service.

@Component

We can use @Component across the application to mark the beans as Spring’s managed components. In DHIS2, any class that is not a Service or a data store and requires to be managed by Spring, can be annotated with @Component.

Bean id

Each annotated Spring bean should have an id corresponding to the full path of the implementing interface.

@Service( "org.hisp.dhis.analytics.AnalyticsTableManager" )
public class JdbcAnalyticsTableManager implements AnalyticsTableManager
{
	...
}

Spring Configuration

Beans that are not defined using prototype annotations, are configured inside ad-hoc classes, annotated with @Configuration. Annotating a class with the @Configuration indicates that the class can be used by the Spring IoC container as a source of bean definitions.

Each @Configuration-annotated class is located in a config package, within each subproject. A simple naming convention has been used when possible to name the @Configuration classes. If a @Configuration contains only services or components, the name is ServiceConfig. If a @Configuration contains only “*Store” classes, the name is StoreConfig.

Additionally, in order to avoid conflicts with @Configuration classes having the same name, each @Configuration-annotated class should have a unique id defined - based on the package name.

For instance, @Configuration( "coreServiceConfig" ).

XML-based configuration

Spring XML-based configuration should be avoided.

Injection

All Spring Beans should only use consutructor-based injection.

  1. All the bean dependencies must be declared as final.
  2. The bean should have one constructor, where all the dependencies are resolved.
  3. The constructor should not be annotated with @Autowired.

Points 1. and 2. are fullfilled by lombok in the following example

import lombok.RequiredArgsConstructor;

@RequiredArgsConstructor
private final UserStore userStore;

    private UserGroupService userGroupService;

    private UserCredentialsStore userCredentialsStore;

    private UserAuthorityGroupStore userAuthorityGroupStore;

    private CurrentUserService currentUserService;

    private SystemSettingManager systemSettingManager;

    private PasswordManager passwordManager;

Bean initialization

Use the @PostConstruct annotation to execute initialization code for a Spring bean.