问题描述
这可能是一个noob问题,但是在很多教程和示例中,我看到这些注释的使用就好像他们做了同样的事情。
然而,我遇到了一些限制使用 @Named
一(特别是依赖注入等)我找不到一个来源的差异被解释,我会非常感谢,如果有人可以粗略概述何时使用一个或另一个。
@Named
给予CDI托管bean一个EL名称用于查看技术,如JSF或JSP。请注意,在CDI应用程序中,您不要需要 @Named
注释来创建由CDI管理的bean(感谢@Karl的评论)
@ManagedBean
使由JSF管理的bean可以:
- 将其注入其他@ManagedBean注释的bean(但不是@Named beans!)
- 通过表达式语言从您的视图中访问它
看到这个,以获取有关注射在两种类型的bean之间如何工作的更多信息。
请注意,与bean的范围不同。它们来自不同的包,但命名相同(JSF: javax.faces.bean
,CDI: javax.enterprise.context
,所以如果你包含错误的类,它通常是一个错误和混乱的根源。
从我的经验来看:尽可能使用CDI bean,因为它们更灵活比JSF管理的bean只有缺点是CDI不知道一个视图范围,所以你需要回到@ManagedBean或使用像Seam这样的第三方扩展。
This might be a noob question, however in a lot of tutorials and examples I saw these annotations used as if they did the same thing.
However I ran into some limitations using the @Named
one (especially with dependency injection etc.) I couldn't find a source where the difference is explained and I'd be very thankful if someone can give a rough overview on when to use one or the other.
@Named
gives a CDI managed bean an EL name to be used in view technologies like JSF or JSP. Note that in a CDI application you don't need the @Named
annotation to make a bean managed by CDI (thanks to @Karl for his comment).
@ManagedBean
makes the bean managed by JSF and you can:
- inject it into other @ManagedBean annotated beans (but not into @Named beans!)
- access it from your views via expression language
See this related question for further information how injection works among both kind of beans.
Note that there is also a difference with the scope of the beans. They come from different packages but are named identically (JSF: javax.faces.bean
, CDI: javax.enterprise.context
, so it is often a source of error and confusion if you include the wrong class.
From my experience: You should use CDI beans whenever possible since they are more flexible than JSF managed beans. Only drawback is that CDI doesn't know a view scope, so you either need to fall back to @ManagedBean or use some third party extension like Seam.
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