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Mock Exam Question:

 
Gareth Llewellyn
Greenhorn
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(The following exam question appears from EJBCertificate.com and is not taken from the real SCBCD exam set.)

What I need is an expert opinion on the why option number 5 is correct. Why can't an EJB class have a package structure? Head First EJB even suggests a package structure is possible given the contents of an ejb jar are the META-INF directory AND the PACKAGE DIRECTORIES. Is this question wrong?? What's all this talk of a security hole? That certainly didn't get mentioned in HFEJB!


Identify correct programming restrictions that a Bean provider must follow to ensure that the enterprise bean is portable and can be deployed in any compliant EJB 2.0 Container. [Select all correct answers]

1 The enterprise bean cannot define read and write to static fields.
2 The enterprise bean cannot make use of the Java Swing API.
3 The enterprise bean cannot make use of interfaces to define business methods.
4 The enterprise bean cannot make use of the Sun JavaMail API.
5 The enterprise bean must not attempt to define a class in a package.

Explanation
Answers 1, 2 and 5 are correct.

Answer 1 is correct. This rule is required to ensure consistent runtime semantics because while some EJB Containers may use a single JVM to execute all enterprise bean's instances, others may distribute the instances across multiple JVMs.

Answer 2 is correct. Most servers do not allow direct interaction between an application program and a keyboard/display attached to the server system.

Answer 5 is correct. This function is reserved for the EJB Container. Allowing the enterprise bean to perform this function would create a security hole.

Answer 3 is incorrect. It is possible to create an interface and implement the interface to make available in the enterprise bean business method.

Answer 4 is incorrect. The enterprise bean can make use of the JavaMail API.
 
B.Sathish
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Refer to page 496 of the spec. The terminology you found is taken directly from the spec. I think this does not refer to the package structure of the bean class or interfaces. We know that they can be in a package. I think this means "the bean class cannot define an inner class in a package". Even I am not very clear about this. Would be glad if Peer or someone else can provide an explanation
 
Ramakrishnan Viswanathan
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There a few posts in this forum with relevance to this discussion. I picked some of them.

http://www.coderanch.com/t/159007/java-EJB-SCBCD/certification/package-class

http://www.coderanch.com/t/158164/java-EJB-SCBCD/certification/EJB-spec

http://www.coderanch.com/t/159917/java-EJB-SCBCD/certification/Imitations-EJB-Model
 
Peer Reynders
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Originally posted by B Sathish:
Would be glad if Peer or someone else can provide an explanation


I've already added my part to the speculation in Help on EJB Programing Restrictions!!.
It certainly looks like the focus is on java.lang.ClassLoader.defineClass() and java.lang.ClassLoader.definePackage()
 
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