JavaEE6 CDI规范的使用1
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2022-08-08
19:42:36
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CDI --Context dependencies Inject 上下文依赖注入，它是一种规范而不是一个具体的实现
一般 JavaEE 应用服务器中默认会提供 CDI 的实现，下面是如何在 tomcat 中使用 CDI
The JSF specification was ahead of the pack when it came to working with and
annotating
managed beans.
However, as the JSF 2.0 specification was getting wrapped up,
another JSR specification, JSR 299, was being developed as well. Frustratingly, JSR 299, the
Contexts and Dependency Injection (CDI) specification, provides a much more flexible and
extendible implementation than the fairly limited JSF implementation. As a result, it's
recommended that if you're developing a JSF application that will be depolyed to a Java EE 6
compliant applicaiton server, then you should be using CDI, and not the standard JSF
annotations.
Having two standards and sets of annotations is pretty confusing. Gavin King stepped into the
fray on the issue of why we have two specifications, and why one should be used instead of
the other. I'd like to take the liberty to quote him on the topic:
Given that EJB and CDI provide arguably more convenient ways to
identify a managed bean, you might wonder precisely what
@ManagedBean is needed for. The answer, as alluded to by Dan, is
that if you have CDI available in your environment (for example, if you
are using EE6), then @ManagedBean is just not really needed.
@ManagedBean is really there for use by people who are using JSF2
without CDI...
To summarize, if you do have CDI available to you, it provides a far
superior programming model to the
@ManagedBean/@ManagedProperty model that JSF2 inherits from
JSF1. So superior, in fact, that the EE 6 web profile does not require
support for @ManagedProperty etc. The idea being that you should
just use CDI instead.
I'm going to recreate the Rock-Paper-Scissors application and use CDI annotations instead of
the JSF ones. To keep things separate, I'm actually going to copy my current, working, JSF
application which is saved in a folder named _easyjsf, and copy it all to a folder named
_easyweld. With that done, I'm going to edit the GameBean to make is Serializable, and to
make it use the CDI annotations that correspond to the JSF annotations we've been using up
to this point.
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