Given an HttpServletRequest request and an EJB SessionContext ctx. Which is a valid way to retrieve the Principal invoking either behavior?

Question

Options

• Arequest.getCallerPrincipal() and ctx.getCallerPrincipal()
• Brequest.getUserPrincipal() and ctx.getUserPrincipal()
• Crequest.getCallerPrincipal() and ctx.getUserPrincipal()
• Drequest.getUserPrincipal() and ctx.getCallerPrincipal()

• A
  94% (31)
• C
  3% (1)
• D
  3% (1)

Explanation

There is an error in the provided answer key - D is actually correct, not A.

HttpServletRequest exposes getUserPrincipal() (Servlet API), while SessionContext exposes getCallerPrincipal() (EJB API). These are two different APIs designed by different specs, which is exactly what option D reflects: request.getUserPrincipal() and ctx.getCallerPrincipal().

Why the other options are wrong:

• A is wrong because HttpServletRequest has no getCallerPrincipal() method - that method belongs to EJBContext only.
• B is wrong because SessionContext has no getUserPrincipal() method - that belongs to the Servlet API only.
• C mixes them the wrong way around: the getCallerPrincipal() call is incorrectly assigned to the request, and getUserPrincipal() to the context.

Memory tip: Think of EJBs as callers in a business-tier invocation chain (getCallerPrincipal), while HTTP requests come from users in a browser (getUserPrincipal). The naming reflects the layer: User → HTTP, Caller → EJB.

Note to you: The answer key provided marks A as correct, but this contradicts the Java EE specification. You may want to verify the source of this question, as it appears to contain a typo or error.

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