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Errata - Java EE Module 1, Chapter 6

27-Apr-2017 in Errata JavaEE

We've recently been made aware of a small issue which affects chapter 6 (the CDI chapter) of Java EE with Wildfly, Module 1. You might experience this issue if you're using some versions of Java 8 to create your project - we're aware it is a problem in Java 8.60 and above.

In the video we talk about the different ways to tell JavaEE which implementation of a particular interface should be injected at runtime, when multiple implementations exist in your project. We first demonstrate the @Default and @Alternative annotations, then we look at specifying the required implementation in beans.xml, and finally we discuss qualifiers, which allow us to specify a different implementation in one specific area of our code.

In the video, we end up with all 3 methods in our project in use at the same time, and this worked fine at the time of recording. However we have found that when you then add in your own custom annotations (such as @ProductionDao - the example we use in the video) the deployment might fail. It appears that there is a bug in Java 8 which means that you can't use custom annotations together with beans.xml.

So you are fine to use @Default and custom annotations together, but not beans.xml and custom annotations. As most users will agree that using @Default and @Alternative are much easier than editing the xml file, this probably won't cause much difficulty in practice, but if you are getting a message that the build has failed, this will be why. If you're following along with the chapter, simply remove beans.xml from your project, and you will be able to continue with no further issues.

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About Matt

I'm a Java developer and trainer for Virtual Pair Programmers, where I present video based training courses on Java, Spring and associated frameworks. I'm currently working on a few different web projects.

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