<init>

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.

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.

 @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.

Author
Chris Beams

Author
Juergen Hoeller

Since
3.0

See Also
LazyBeanComponentScanorg.springframework.stereotype.Component