@Target(value={TYPE,METHOD}) @Retention(value=RUNTIME) @Documented public @interface Primary
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.
Lazy
,
Bean
,
ComponentScan
,
Component