@Target({TYPE,METHOD}) @Retention(RUNTIME) @Documented public @interface Primary

Indicates that a bean should be given preference when multiple candidates are qualified to autowire a single-valued dependency. If exactly one 'primary' bean exists among the candidates, it will be the autowired value.

Primary beans only have an effect when finding multiple candidates for single injection points. All type-matching beans are included when autowiring arrays, collections, maps, or ObjectProvider streams.

This annotation is semantically equivalent to the <bean> element's primary attribute in Spring XML.

May be used on any class directly or indirectly annotated with @Component or on methods annotated with @Bean.

Example

 @Component
 public class FooService {

     private FooRepository fooRepository;

     @Autowired
     public FooService(FooRepository fooRepository) {
         this.fooRepository = fooRepository;
     }
 }

 @Component
 public class JdbcFooRepository extends FooRepository {

     public JdbcFooRepository(DataSource dataSource) {
         // ...
     }
 }

 @Primary
 @Component
 public class HibernateFooRepository extends FooRepository {

     public HibernateFooRepository(SessionFactory sessionFactory) {
         // ...
     }
 }

Because HibernateFooRepository is marked with @Primary, it will be injected preferentially over the jdbc-based variant assuming both are present as beans within the same Spring application context, which is often the case when component-scanning is applied liberally.

Note that using @Primary at the class level has no effect unless component-scanning is being used. If a @Primary-annotated class is declared via XML, @Primary annotation metadata is ignored, and <bean primary="true|false"/> is respected instead.

Since:

3.0

Author:

Chris Beams, Juergen Hoeller

See Also:

Annotation Interface Primary

Example