应用场景：

当有时候要在一个长生命周期的bean里面生命一个较短生命周期的应用的时候（例如在一个Singolton的bean里生命一个session bean），如果直接使用会发现创建Bean失败。

@Scope("session")
public SessionBean {
}

@Scope("singoleton")
public SingletonBean {
     @Inject
      private SessionBean sessionBean
}
这时候会抛出这样的异常：

Caused by: org.springframework.beans.factory.BeanCreationException: 
Could not autowire field: private SessionBeanSingletonBEan.SessionBean; 
nested exception is org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'SessionBean': Scope 'session' is not active 
for the current thread; consider defining a scoped proxy for this bean if 
you intend to refer to it from a singleton; nested exception is
java.lang.IllegalStateException: No thread-bound request found: Are you referring 
to request attributes outside of an actual web request, or processing a request 
outside of the originally receiving thread? If you are actually operating within 
a web request and still receive this message, your code is 
probably running outside of DispatcherServlet/DispatcherPortlet: In this case, 
use RequestContextListener or RequestContextFilter to expose the current request.

解决方案：

1. Lookup method inject 具体可以参考这里

2. 使用代理注入bean， 在调用的时候决定使用哪一个实例化的被引用bean

@Scope(value = "session", proxyMode = ScopedProxyMode.TARGET_CLASS)
public SessionBean {
}

@Scope("singoleton")
public SingletonBean {
     @Inject
      private SessionBean sessionBean
}

或者：

<bean name="singletonBean" class="somepkg.SingletonBean"> 
<property name="someProperty" ref="sessionBean"/> 
</bean> 

<bean name="sessionBean" class="somepkg.SessionBean" scope="session"> 
<aop:scoped-proxy/> 
</bean> 

这个在Refer spring-framework-reference 3.0，  Section 3.5 - Bean scopes, Sub topic - Scoped beans as dependencies 中有详细的论述。