BEA WebLogic Interview Questions and Answers 16

Which is the only method defined in the javax.ejb.Handle interface?
a. getEJBhome
b. getEJBObject
c. getPrimaryKey
d. gethomeHandle

Choice B is correct. The Handle is a serializable reference to the EJBObject. The EJBObject.getHandle() method returns a Handle object. The Handle allows us to recreate an EJB object remote reference that points to the same type of session bean or the same unique bean that the handle came from.
The Handle interface specifies only one method, getEJBObject(). Calling this method returns the EJB Object from which the handle was created. After getting the object back, we can narrow or cast it to the appropriate remote interface type. The getEJBhome method is defined in the homeHandle interface and the getPrimaryKey method in the Entity Context interface. The gethomeHandle method is defined in the EJBhome interface.

In CORBA, which of the following files generated by the "idltojava" compiler must be compiled before running the server application?
a. Only The Holder Classes
b. Only The Helper and Holder Classes
c. The implementation class(es) written by the user to provide body to the methods defined in the interface class
d. All idltojava generated files (stubs, skeletons, helper, holder and interface classes)

Choice C and D are correct. The Helper class (a final class) provides auxiliary functionality, notably the narrow() method required to cast CORBA object references to their proper types. The Holder class provides operations for out and in out arguments, which CORBA has but which do not map easily to Java's semantics. The server application cannot be compiled successfully until the implementation class(es) has/have been written and compiled. All the other generated files however must be compiled to form '.class' files from the '.java' files. Thus all the implementation classes written by the user and all the "idltojava" generated files must be complied to run the CORBA Server.

Considering the code below, which of the lines of code (given in the choices) should be placed at line 4 to make this JSP prints "My score is : 100"? Please ignore the line numbers for the purpose of validity of the JSP code.
1:
2:
3:
My Progress Report
4:
5: <% score++; %>
6: <%= "My score is : " + score %>
7:
8:
a. <%! int score = 99; %>
` b. <% int score; %> `
c. <%@ int score = 99; %>
` d. < score =" 99;">

A is the correct choice. The above JSP will work on declaring and initializing the variable score. The syntax for declaring and initializing a variable in JSP is as follows:

<%! variable=variable_value ; %>

Thus A is the correct choice. The <%@ ... %> tag is used to declare directives like include directive. Thus choice C is incorrect. The <% ... %> code is used to insert scriptlet (lines of code in java) like the one at line 5. The code written inside the scriptlet becomes part of the service() method of the generated Servlet. Thus 'score' becomes the local variable of the service method. And for this JSP to compile properly, the variable 'score' should have been initialized. If "<% int score; %>" is replaced by "<% int score=99; %>" , the choice B would also be correct. In the present scenario, the choice B will give compilation error saying "Variable score may not have been initialized". Choice D is incorrect as it's not a valid tag.

How do I increase WebLogic Server memory?
Increase the allocation of Java heap memory for WebLogic Server. (Set the minimum and the maximum to the same size.) Start WebLogic Server with the -ms32m option to increase the allocation, as in this example:
$ java ... -ms32m -mx32m ...
This allocates 32 megabytes of Java heap memory to WebLogic Server, which improves performance and allows WebLogic Server to handle more simultaneous connections. You can increase this value if necessary.

What causes Java.io exceptions in the log file?
You may see messages like these in the log file:
(Windows NT)
java.io.IOException Connection Reset by Peer
java.io.IOException Connection Reset by Peer

(Solaris)
java.io.Exception: Broken pipe
These messages occur when you are using servlets. A client initiates an HTTP request, and then performs a series of actions on the browser:
1. Click Stop or enter equivalent command or keystrokes
2. Click Refresh or enter equivalent command or keystrokes
3. Send a new HTTP request.
The messages indicate that WebLogic Server has detected and recovered from an interrupted HTTP request.

Java-CORBA integration: RMI-IIOP or Java IDL?
It is important to understand the distinction between these two ways of integrating Java with CORBA.
RMI-IIOP is for Java programmers who want to program to the RMI interfaces but use IIOP as the underlying transport. RMI-IIOP provides interoperability with other CORBA objects implemented in various languages, but only if all the remote interfaces are originally defined as Java RMI interfaces. It is of particular interest to programmers using Enterprise JavaBeans (EJBs), because the remote object model for EJB is RMI-based.
Java IDL is for CORBA programmers who want to program in Java based on interfaces defined in CORBA IDL. This is "business as usual" CORBA programming, supporting Java in exactly the same way as other languages like C++ or COBOL.

How do an RMI-IIOP application and an existing CORBA object interoperate?
If the existing CORBA object has its remote interfaces defined originally in CORBA IDL, then interoperability is not possible. RMI-IIOP applications can interoperate with other CORBA objects only when their remote interfaces are originally defined as Java RMI interfaces.
For example, to interoperate between an RMI-IIOP client and a C++ object you need to:
1. Define the remote interface of the object in Java as an RMI interface.
2. Run rmic -iiop against the interface to produce the stub for your RMI-IIOP client.
3. Run rmic -idl against the interface to produce IDL compatible with the RMI interface.
4. Run a C++ stub compiler against the IDL file to produce the C++ skeleton for your C++ server object