Younghoe.Info (final edition)

I found the difference between the javadoc for the @Bean annotation and the reference doc in RC 3.0 release.

The javadoc reads:

• <h3>Constraints</h3>
• <ul>
• <li>Bean methods are valid only when declared within an {@link Configuration @Configuration}-annotated class

But, the reference(3.10.4 Defining bean metadata within components) says:

@Component
public class FactoryMethodComponent {

private static int i;

@Bean @Qualifier("public")
public TestBean publicInstance() { return new TestBean("publicInstance"); }

Constraints

• Bean methods are valid only when declared within an {@link Configuration @Configuration}-annotated class
• Bean methods must be non-void, non-final, non-private
• Bean methods may not accept any arguments
• Bean methods may throw any exception, which will be caught and handled by the Spring container on processing of the declaring {@link Configuration @Configuration} class.

Usage

Bean methods may reference other Bean methods by calling them directly. This ensures that references between beans are strongly typed and navigable. So called 'inter-bean references' are guaranteed to respect scoping and AOP semantics.

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.

@Component
public class FactoryMethodComponent {

    private static int i;

    @Bean @Qualifier("public")
    public TestBean publicInstance() {
        return new TestBean("publicInstance");
    }

    // use of a custom qualifier and autowiring of method parameters

    @Bean @BeanAge(1)
    protected TestBean protectedInstance(@Qualifier("public") TestBean spouse,
                                         @Value("#{privateInstance.age}") String country) {
        TestBean tb = new TestBean("protectedInstance", 1);
        tb.setSpouse(tb);
        tb.setCountry(country);
        return tb;
    }

    @Bean @Scope(BeanDefinition.SCOPE_SINGLETON)
    private TestBean privateInstance() {
        return new TestBean("privateInstance", i++);
    }

    @Bean @Scope(value = WebApplicationContext.SCOPE_SESSION,
                 proxyMode = ScopedProxyMode.TARGET_CLASS)
    public TestBean requestScopedInstance() {
        return new TestBean("requestScopedInstance", 3);
    }
}