How does Wicket's @SpringBean annotation work?

How does Wicket's @SpringBean annotation work? Does it use reflection at run time? Does it make the compiler inject some code开发者_如何学C? Or what?

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@SpringBean works using Wicket's underlying Injector mechanism. When you instantiate a Wicket component, the constructor of Wicket's component base class introspects the class being instantiated, looking for the @SpringBean annotation. If the bean is found, then Wicket generates a proxy for the spring bean and injects it into the component's field. This is Wicket's equivalent of Spring's @Autowired annotation, the effect is similar.

It doesn't, however, have anything to do with Spring's own context/classpath scanning functionality (e.g. @Component), which is about auto-discovery of what is and isn't a bean, rather having anything to do with wiring.

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The class marked with a @SpringBean annotation has to have one of:

1. A no-args constructor
2. A superclass with a no-args constructor
3. Implement an interface

An exception will be thrown if these conditions are not met as Wicket will not be able to proxy the class.

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Spring uses the class loader and ASM at runtime to find all annotated classes.

You can configure where spring should search for beans:

<context:component-scan base-package="some.package.to.start.from"/>

This uses the ClassPathBeanDefinitionScanner internally which will use the PathMatchingResourcePatternResolver to find the classes and the ASM-based MetadataReader to read the annotations.