Struts 2 and Spring how struts-created objects han

Question

We are using Struts 2 with spring frame work 4 (https://struts.apache.org/docs/spring-plugin.html). I have some question about Struts bean creation.

When we use Struts with Spring we can easily use spring @Inject, @Value, @Resource in Actions, Validators and Interceptors, without annotating any of them as @Component (or @Named). This seems that struts-created objects are spring managed beans.

This is not true, because when you look at applicationContext.getBeanDefinitionNames() you can not find any action, validator or interceptor.

So if Struts-created objects are not spring manage beans, why the spring annotations ( @Inject, @Value, ...) works quite well?

Is it technically possible that we create a new object (after spring start up) and pass it to Spring and let Spring setup it? How?!

Answer 1

Struts uses an ObjectFactory to build any object like actions, interceptors, validators, etc.:

ObjectFactory is responsible for building the core framework objects. Users may register their own implementation of the ObjectFactory to control instantiation of these Objects.

Struts-Spring plugin registers its own object factory StrutsSpringObjectFactory:

Struts object factory that integrates with Spring.

There, it overrides methods building Objects, such as buildBean().

Now if you look at the implementation, it is using method org.springframework.beans.factory.config.AutowireCapableBeanFactory#createBean()

which generally creates a new instance of the clazz argument.

Central method of this class: creates a bean instance, populates the bean instance, applies post-processors, etc.

Then, the newly created instance is passed for autowiring with org.springframework.beans.factory.config.AutowireCapableBeanFactory#autowireBeanProperties()

After that, this instance is passed to Guice for injection.

Now it's fully baked and ready to return.

---

Note that, if the bean is managed by Spring, it uses getBean method from application context, otherwise the new instance is created always by struts-spring plugin if the bean is not managed by Spring.