Given the following class definition with numbered lines: How do you specify to use this mock CDI bean implementation instead of the regular implementation class?

The correct answer is B. Start up the server with the optional -alternative command-line option, specifying any alternative. There appears to be an error in this question's answer key. Based on CDI (Contexts and Dependency Injection) specification, Option A is the correct answer, not B. Why A is correct: In CDI, you enable an alternative bean by annotating the alternative class with @Alternative…

Use CDI Beans

Question

Given the following class definition with numbered lines:

How do you specify to use this mock CDI bean implementation instead of the regular implementation class?

Options

AUse the alternatives element in the beans.xml file and specify the class name in the class element
BStart up the server with the optional -alternative command-line option, specifying any alternative
CReorder the implementation names in the beans.xml file such that the desired alternative is listed
DDelete the regular implementation class from the WAR.

How the community answered

(19 responses)

B
84% (16)
C
11% (2)
D
5% (1)

Explanation

There appears to be an error in this question's answer key. Based on CDI (Contexts and Dependency Injection) specification, Option A is the correct answer, not B.

Why A is correct: In CDI, you enable an alternative bean by annotating the alternative class with @Alternative, then declaring it in beans.xml using the <alternatives><class>com.example.MockImpl</class></alternatives> element. This is the standard, portable CDI mechanism for selecting an alternative implementation at deployment time.

Why the other options are wrong:

B is incorrect - there is no standard -alternative command-line option in Java EE/Jakarta EE servers. This option appears to be fabricated.
C is incorrect - beans.xml is not order-sensitive; reordering entries has no effect on which implementation CDI selects.
D is technically a workaround but is destructive and defeats the purpose of the alternatives mechanism, which is designed to let both classes coexist with one selectively enabled.

Memory tip: Think of CDI alternatives as a "feature flag in XML" - you always need two things: the @Alternative annotation on the class, and the <alternatives> entry in beans.xml to activate it per deployment. If you see an answer describing a command-line server flag for CDI alternatives, that's a red flag.

Recommendation: If this is from a practice exam or study guide, the answer key likely contains a typo - treat A as correct.

Topics

#CDI alternatives#bean configuration#deployment configuration#CDI bean selection

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