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EJB interview questions

  • what are Container-Managed Transactional attributes ? view answer
  • What's difference between httpsession and EJB session bean ? view answer
  • What are the Differences between EJB 3.0 and EJB 2.1? view answer
  • Q. what are Container-Managed Transactional arributes ? view answer
  • What is the default transaction attribute for an EJB? view answer
  • Difference between SessionBean remove() and EntityBean remove() method? view answer
  • Why do we have a remove method in both EJBHome and EJBObject? view answer
  • Is it possible to share an HttpSession between a JSP and EJB? What happens when I change a value in the HttpSession from inside an EJB? view answer
  • What is the difference between a ?Coarse Grained? Entity Bean and a ?Fine Grained? Entity Bean? view answer
  • What are the Interfaces need to create to implement Session Bean with Exmaple? view answer
  • What are the parameters must follow for Session Bean ? view answer
  • What are the callbacks method in Session Bean ? view answer
  • What are the ways for a client application to get an EJB object? view answer
  • What is handle and why it is used in EJB? view answer
  • What is an EJB Context? view answer
  • Implement Local and Remote Interfaces in EJB? view answer
  • How can I call one EJB from inside of another EJB? view answer
  • What is the difference between Message Driven Beans and Stateless Session beans? view answer
  • What happens if remove( ) is never invoked on a session bean? view answer
  • Can you control when passivation occurs? view answer
  • Can the primary key in the entity bean be a Java primitive type such as int? view answer
  • The EJB container implements the EJBHome and EJBObject classes. For every request from a unique client, does the container create a separate instance of the generated EJBHome and EJBObject classes? view answer
  • How can i maintain a user session between servlets and stateful session ejbs? view answer
  • What's difference between Servlet/JSP session and EJB session view answer
  • Is it possible to share an HttpSession between a JSP and EJB? What happens when I change a value in the HttpSession from inside an EJB? view answer
  • How to call any EJB from a servlet/JSP/Java Client? view answer
  • What are transaction isolation levels in EJB? view answer
  • What are transaction attributes? view answer
  • What is bean managed transaction? view answer
  • Can Entity Beans have no create() methods? view answer
  • What are the callback methods in Entity beans? view answer
  • What is the difference between Container-Managed Persistent (CMP) bean and Bean-Managed Persistent(BMP) ? view answer
  • What are the methods of Entity Bean? view answer
  • What is Entity Bean? view answer
  • What is Session Bean? view answer
  • What are the different kinds of enterprise beans? view answer

!!! EJB interview questions !!!

What are the Interfaces need to create to implement Session Bean with Exmaple?



Session bean class (CartBean)
Home interface (CartHome)
Remote interface (Cart)

Session bean class (CartBean) :
public class CartBean implements SessionBean {

String customerName;
String customerId;
Vector contents;

public void ejbCreate(String person)
throws CreateException {

if (person == null) {
throw new CreateException("Null person not allowed.");
}
else {
customerName = person;
}

customerId = "0";
contents = new Vector();
}

public void ejbCreate(String person, String id)
throws CreateException {

if (person == null) {
throw new CreateException("Null person not allowed.");
}
else {
customerName = person;
}

IdVerifier idChecker = new IdVerifier();
if (idChecker.validate(id)) {
customerId = id;
}
else {
throw new CreateException("Invalid id: "+ id);
}

contents = new Vector();
}

public void addBook(String title) {
contents.addElement(title);
}

public void removeBook(String title) throws BookException {

boolean result = contents.removeElement(title);
if (result == false) {
throw new BookException(title + "not in cart.");
}
}

public Vector getContents() {
return contents;
}

public CartBean() {}
public void ejbRemove() {}
public void ejbActivate() {}
public void ejbPassivate() {}
public void setSessionContext(SessionContext sc) {}

}


Home Interface:
public interface CartHome extends EJBHome {
Cart create(String person) throws
RemoteException, CreateException;
Cart create(String person, String id) throws
RemoteException, CreateException;
}

The signatures of the ejbCreate and create methods are similar, but differ in important ways. The rules for defining the signatures of the create methods of a home interface follow.

The number and types of arguments in a create method must match those of its corresponding ejbCreate method.
The arguments and return type of the create method must be valid RMI types.
A create method returns the remote interface type of the enterprise bean. (But an ejbCreate method returns void.)
The throws clause of the create method must include the java.rmi.RemoteException and the javax.ejb.CreateException

Remote Interface :
public interface Cart extends EJBObject {

public void addBook(String title) throws RemoteException;
public void removeBook(String title) throws
BookException, RemoteException;
public Vector getContents() throws RemoteException;
}
The method definitions in a remote interface must follow these rules:

Each method in the remote interface must match a method implemented in the enterprise bean class.
The signatures of the methods in the remote interface must be identical to the signatures of the corresponding methods in the enterprise bean class.
The arguments and return values must be valid RMI types.
The throws clause must include the java.rmi.RemoteException



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