barcode font vb.net If you re using a JMS resource, the differences between EJB 2 and EJB 3 are shown in table 14.4. in Java

Generator Data Matrix ECC200 in Java If you re using a JMS resource, the differences between EJB 2 and EJB 3 are shown in table 14.4.

If you re using a JMS resource, the differences between EJB 2 and EJB 3 are shown in table 14.4.
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Table 14.4 The use of JMS objects in EJB 2 was also very complex and has been simplified in EJB 3 by using dependency injection. EJB 2.x Define resource-ref in ejb-jar.xml Lookup resource Context ctx = new InitialContext(); QueueConnectionFactory qcf = (QueueConnectionFactory) ctx.lookup("java:comp/env/jms/Queue ConnectionFactory"); QueueConnection conn = qcf.createQueueConnection(); EJB3 @Resource(name = "jms/QueueConnectionFactory") private QueueConnectionFactory qcf;
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QueueConnection conn = qcf. createQueueConnection();
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Migrating session beans
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Our comparison on how resources are declared and found between EJB 2 and EJB 3 is intended to underscore how much more straightforward dependency injection is compared to JNDI (no casting required), and how much easier it is for developers to maintain.
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14.2.3 Transactions and security settings
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EJB 2 doesn t define any default transaction and security settings for EJBs. You have to specify the definitions yourself for each and every bean method in a session bean. If you don t, you ll see different behaviors in different EJB containers. As discussed in chapter 6, EJB 3 defines CMT as the default transaction management type for a bean, and REQUIRED as the default transaction attribute for bean methods. Therefore, you can simplify your transaction settings in your deployment descriptors by only specifying those that need a transaction attribute other than REQUIRED. Optionally, you can use annotations to define transaction settings. The same holds true for security settings. You can leave the security settings as is in the deployment descriptor, or use the security annotations discussed in chapter 6.
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14.2.4 Client applications
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Session beans are server-side components that encapsulate business logic and may be accessed either by remote or local clients. The client for an EJB could be another EJB in the same container, a separate container, a web module, or an application client. When you migrate any session bean to EJB 3, the clients will be impacted. This is mostly due to the fact that home interfaces are no longer needed. All client applications will have to be modified to use the EJB 3 client view. The ejb-ref or ejb-local-ref element in the client application s descriptor will also need to be modified to remove the home element, and the client code will have to be updated to look up the business interface instead of the home interface. The old EJB 2 client code for the PlaceBid session bean would look like this:
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Context context = new InitialContext(); PlaceBidHome placeBidHome = (PlaceBidHome) PortableRemoteObject.narrow( context.lookup("java:comp/env/PlaceBid"), PlaceBidHome.class); PlaceBid placeBid = placeBidHome.create(); newBidId = placeBid.addBid(userId, itemId, bidPrice);
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The migrated client code for the PlaceBid EJB will look like this if you continue to use JNDI:
Migrating to EJB 3
Context context = new InitialContext(); PlaceBid placeBid = (PlaceBid)context.lookup("java:comp/env/PlaceBid"); Long newBidId = placeBid.addBid(userId, itemId, bidPrice);
If your client is a managed class and uses the Java EE 5 API, you can migrate the client to use dependency injection and further simplify the client code:
@EJB private PlaceBid placeBid; Long newBidId = placeBid.addBid(userId, itemId, bidPrice);
So the original EJB 2 lookup took around eight lines of code. The EJB 3 refactoring reduced this to two lines of code, regardless of whether you use JNDI or dependency injection in this case. Of course, your mileage may vary but we think you ll immediately see some benefits to migrating this code to the new programming model available in EJB 3. Maintaining backward compatibility with EJB 2 clients There may be various cases when you cannot afford to migrate your client applications, but you want to move your session beans to EJB 3. This will primarily be an issue when you have a remote interface for a session bean that is used by separate applications, some of which you don t have control over. Or perhaps you re an independent software vendor (ISV) that sells packaged applications and customers may be using your EJB in their EJB 2 applications. To demonstrate this, imagine that many ActionBazaar Gold customers use rich client applications that remotely access EJBs such as PlaceBid. Now that PlaceBid has been migrated to EJB 3 (POJOs, regular interface, etc.), the rich client applications will break unless you update them. In this release of ActionBazaar you aren t making any client-side changes because you don t want to distribute a newer version of client applications to your customers. At the same time you don t want your client applications to break. Client applications of EJB 2 session beans use the create method on the home interface to create an EJB object instance. You can add a home interface and expose a create method in the home interface as follows:
import javax.rmi.RemoteException; import javax.ejb.*; public interface PlaceBidHome extends EJBHome { public PlaceBid create() throws CreateException, RemoteException; }
Then use the @RemoteHome annotation on the bean class to mark this as a remote home interface as follows:
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