Spring Prototype scoped bean in a singleton

From Spring documentation:

You do not need to use the <aop:scoped-proxy/> in conjunction with beans that are scoped as singletons or prototypes. If you try to create a scoped proxy for a singleton bean, the BeanCreationException is raised.

It seems the documentation has changed a bit for version 3.2 documentation where you can find this sentence:

You do not need to use the <aop:scoped-proxy/> in conjunction with beans that are scoped as singletons or prototypes.

It seems that its not expected you use a proxied prototype bean, as each time it is requested to the BeanFactory it will create a new instance of it.

---

In order to have a kind of factory for your prototype bean you could use an ObjectFactory as follows:

@Component
public class SingletonBean {

    @Autowired
    private ObjectFactory<PrototypeBean> prototypeFactory;

    public void doSomething() {
        PrototypeBean prototypeBean = prototypeFactory.getObject();
        prototypeBean.setX(1);
        prototypeBean.display();
    }
}

and your prototype bean would be declared as follows:

@Component 
@Scope(value="prototype")
public class PrototypeBean {
    // ...
}

Singleton bean is created only once so the prototype bean which is injected also will be created once at the instantiation of singleton bean.The same instance of prototype bean will be used for every request.

If new instance of prototype bean will be created for each request at runtime ,the below method Injection can be used

Example

public class Singleton {
    private Prototype prototype;

    public Singleton(Prototype prototype) {
        this.prototype = prototype;
    }

    public void doSomething() {
         prototype.foo();
    }

    public void doSomethingElse() {
        prototype.bar();
    }
}

public abstract class Singleton {
    protected abstract Prototype createPrototype();

    public void doSomething() {
        createPrototype().foo();
    }

    public void doSomethingElse() {
        createPrototype().bar();
    }
}


<bean id="prototype" class="ch.frankel.blog.Prototype" scope="prototype" />
<bean id="singleton" class="sample.MySingleton">
   <lookup-method name="createPrototype" bean="prototype" />
</bean>