org.springframework.context.annotation
Annotation Type Bean

@Target(value={METHOD,ANNOTATION_TYPE})
@Retention(value=RUNTIME)
@Documented
public @interface Bean

Indicates that a method produces a bean to be managed by the Spring container. The names and semantics of the attributes to this annotation are intentionally similar to those of the <bean/> element in the Spring XML schema.

Note that the @Bean annotation does not provide attributes for scope, primary or lazy. Rather, it should be used in conjunction with @Scope, @Primary, and @Lazy annotations to achieve those semantics. The same annotations can also be used at the type level, e.g. for component scanning.

While a name() attribute is available, the default strategy for determining the name of a bean is to use the name of the Bean method. This is convenient and intuitive, but if explicit naming is desired, the name() attribute may be used. Also note that name() accepts an array of Strings. This is in order to allow for specifying multiple names (i.e., aliases) for a single bean.

The @Bean annotation may be used on any methods in an @Component class, in which case they will get processed in a configuration class 'lite' mode where they will simply be called as plain factory methods from the container (similar to factory-method declarations in XML). The containing component classes remain unmodified in this case, and there are no unusual constraints for factory methods.

As an advanced mode, @Bean may also be used within @Configuration component classes. In this case, bean methods may reference other @Bean methods on the same class by calling them directly. This ensures that references between beans are strongly typed and navigable. Such so-called 'inter-bean references' are guaranteed to respect scoping and AOP semantics, just like getBean lookups would. These are the semantics known from the original 'Spring JavaConfig' project which require CGLIB subclassing of each such configuration class at runtime. As a consequence, configuration classes and their factory methods must not be marked as final or private in this mode.

A note on BeanFactoryPostProcessor-returning @Bean methods

Special consideration must be taken for @Bean methods that return Spring BeanFactoryPostProcessor (BFPP) types. Because BFPP objects must be instantiated very early in the container lifecycle, they can interfere with processing of annotations such as @Autowired, @Value, and @PostConstruct within @Configuration classes. To avoid these lifecycle issues, mark BFPP-returning @Bean methods as static. For example:

     @Bean
     public static PropertyPlaceholderConfigurer ppc() {
         // instantiate, configure and return ppc ...
     }

By marking this method as static, it can be invoked without causing instantiation of its declaring @Configuration class, thus avoiding the above-mentioned lifecycle conflicts. Note however that static @Bean methods will not be enhanced for scoping and AOP semantics as mentioned above. This works out in BFPP cases, as they are not typically referenced by other @Bean methods. As a reminder, a WARN-level log message will be issued for any non-static @Bean methods having a return type assignable to BeanFactoryPostProcessor.

Since:

3.0

Author:

Rod Johnson, Costin Leau, Chris Beams, Juergen Hoeller

See Also:

Component, Configuration, Scope, DependsOn, Lazy, Primary, Autowired, Value

Optional Element Summary

Autowire	autowire Are dependencies to be injected via autowiring?
String	destroyMethod The optional name of a method to call on the bean instance upon closing the application context, for example a close() method on a DataSource.
String	initMethod The optional name of a method to call on the bean instance during initialization.
String[]	name The name of this bean, or if plural, aliases for this bean.

name

public abstract String[] name

The name of this bean, or if plural, aliases for this bean. If left unspecified the name of the bean is the name of the annotated method. If specified, the method name is ignored.

Default:

{}

autowire

public abstract Autowire autowire

Are dependencies to be injected via autowiring?

Default:

org.springframework.beans.factory.annotation.Autowire.NO

initMethod

public abstract String initMethod

The optional name of a method to call on the bean instance during initialization. Not commonly used, given that the method may be called programmatically directly within the body of a Bean-annotated method.

Default:

""

destroyMethod

public abstract String destroyMethod

The optional name of a method to call on the bean instance upon closing the application context, for example a close() method on a DataSource. The method must have no arguments but may throw any exception.

Note: Only invoked on beans whose lifecycle is under the full control of the factory, which is always the case for singletons but not guaranteed for any other scope.

See Also:

ConfigurableApplicationContext.close()

Default:

""