Why the following does not work for autowired

I have a class like

class A {
      @Autowired
      B b;
}

A a = new A()

I found b is not autowired

I already did &l开发者_JAVA百科t;context:component-scan base-package="*">, anything else missing?

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You have to get the bean from a bean factory, instead of creating an instance directly.

For example, here's how to do it with annotations. First, you need to add a bit more to your declaration of your class:

// Annotate to declare this as a bean, not just a POJO
@Component
class A {
    @Autowired
    B b;
}

Next, you do this once per application:

AnnotationConfigApplicationContext factory =
        new AnnotationConfigApplicationContext();
factory.register(A.class);
factory.register(B.class);
// Plus any other classes to register, or use scan(packages...) method
factory.refresh();

Finally, you can now get instances of the bean:

// Instead of: new A()
A a = factory.getBean(A.class);

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Spring will only autowire the A object if Spring instantiates it as a bean. if you instantiate your own, Spring knows nothing about it, so nothing gets autowired.