barcode font vb.net The @TransactionAttribute annotation in Java

Drawer DataMatrix in Java The @TransactionAttribute annotation

6.2.3 The @TransactionAttribute annotation
Draw Data Matrix In Java
Using Barcode creation for Java Control to generate, create Data Matrix 2d barcode image in Java applications.
www.OnBarcode.com
Decode Data Matrix In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Although the container does most of the heavy lifting in CMT, you still need to tell the container how it should manage transactions. To understand what this means, consider the fact that the transaction which wraps around your bean s method could be started by the container specifically when calling your method, or it could be inherited from a client calling your method (otherwise called joining a transaction). Let s explore this idea a little more using our example. The placeSnagItOrder method in listing 6.1 calls a number of methods such as bidsExisting, validateCredit, chargeCustomer, and removeItemFromBidding. As figure 6.3 shows, these method calls could simply be forwarded to other session bean invocations, such as BidManagerBean.bidsExist, BillingManagerBean.validateCredit, BillingManagerBean.chargeCustomer, and ItemManagerBean.removeFromBidding. We already know that the placeSnagItOrder method is managed by a transaction. What if all the session beans we are invoking are also managed by CMT Should the container reuse the transaction created for our method to invoke the other methods Should our existing transaction be independent of the other session beans transactions What happens if any of the methods cannot support transactions The @TransactionAttribute annotation tells the container how to handle all these situations. The annotation can be applied either to individual CMT bean methods or to the entire bean. If the annotation is applied at the bean
1D Barcode Creation In Java
Using Barcode encoder for Java Control to generate, create Linear image in Java applications.
www.OnBarcode.com
Make European Article Number 13 In Java
Using Barcode generator for Java Control to generate, create EAN13 image in Java applications.
www.OnBarcode.com
Figure 6.3 The method invocations from the CMT session bean is actually forwarded to other session beans that may be using various transaction attributes.
UPC-A Generation In Java
Using Barcode printer for Java Control to generate, create GS1 - 12 image in Java applications.
www.OnBarcode.com
Draw UCC.EAN - 128 In Java
Using Barcode creation for Java Control to generate, create GTIN - 128 image in Java applications.
www.OnBarcode.com
Transactions and security
Printing Code-39 In Java
Using Barcode generator for Java Control to generate, create ANSI/AIM Code 39 image in Java applications.
www.OnBarcode.com
Generating RM4SCC In Java
Using Barcode printer for Java Control to generate, create RM4SCC image in Java applications.
www.OnBarcode.com
level, all business methods in the bean inherit the transaction attribute value specified by it. In listing 6.1, we specify that the value of the @TransactionAttribute annotation for the placeSnagItOrder method should be TransactionAttributeType.REQUIRED. There are six choices for this annotation defined by the enumerated type TransactionAttributeType. Table 6.2 summarizes their behavior.
Data Matrix 2d Barcode Creation In Java
Using Barcode generation for Java Control to generate, create Data Matrix 2d barcode image in Java applications.
www.OnBarcode.com
Data Matrix ECC200 Reader In Visual Studio .NET
Using Barcode decoder for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Table 6.2 Effects of transaction attributes on EJB methods Caller Transaction Exists No Yes REQUIRES_NEW No Yes Effect Container creates a new transaction. Method joins the caller s transaction. Container creates a new transaction. Container creates a new transaction and the caller s transaction is suspended. No transaction is used. Method joins the caller s transaction. javax.ejb.EJBTransactionRequiredException is thrown. Method joins the caller s transaction. No transaction is used. The caller s transaction is suspended and the method is called without a transaction. No transaction is used. javax.ejb.EJBException is thrown.
Generate EAN128 In None
Using Barcode maker for Office Word Control to generate, create USS-128 image in Office Word applications.
www.OnBarcode.com
Create Code 3 Of 9 In Objective-C
Using Barcode maker for iPhone Control to generate, create Code-39 image in iPhone applications.
www.OnBarcode.com
Transaction Attribute REQUIRED
Generating UPC A In Java
Using Barcode drawer for Android Control to generate, create UPC-A Supplement 2 image in Android applications.
www.OnBarcode.com
GS1 - 13 Decoder In Java
Using Barcode recognizer for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
SUPPORTS
Encode UPC-A Supplement 5 In .NET
Using Barcode creator for Reporting Service Control to generate, create UCC - 12 image in Reporting Service applications.
www.OnBarcode.com
EAN / UCC - 13 Creator In .NET Framework
Using Barcode creation for ASP.NET Control to generate, create UPC - 13 image in ASP.NET applications.
www.OnBarcode.com
No Yes
ANSI/AIM Code 128 Printer In None
Using Barcode printer for Office Word Control to generate, create Code 128 Code Set C image in Office Word applications.
www.OnBarcode.com
Making EAN 13 In None
Using Barcode printer for Microsoft Excel Control to generate, create EAN-13 Supplement 5 image in Office Excel applications.
www.OnBarcode.com
MANDATORY
Barcode Maker In .NET Framework
Using Barcode generation for Reporting Service Control to generate, create Barcode image in Reporting Service applications.
www.OnBarcode.com
Generate USS Code 39 In Java
Using Barcode printer for Android Control to generate, create Code 3/9 image in Android applications.
www.OnBarcode.com
Yes NOT_SUPPORTED No Yes
NEVER
No Yes
Let s take a look at what each value means and where each is applicable. REQUIRED REQUIRED is the default and most commonly applicable transaction attribute value. This value specifies that the EJB method must always be invoked within a transaction. If the method is invoked from a nontransactional client, the container will start a transaction before the method is called and finish it when the method returns. On the other hand, if the caller invokes the method from a transactional context, the method will join the existing transaction. In case of transactions
Container-managed transactions
propagated from the client, if our method indicates that the transaction should be rolled back, the container will not only roll back the whole transaction but will also throw a javax.transaction.RollbackException back to the client. This lets the client know that the transaction it started has been rolled back by another method. Our placeSnagItOrder method is most likely invoked from a nontransactional web tier. Hence, the REQUIRED value in the @TransactionAttribute annotation will cause the container to create a brand-new transaction for us when the method is executed. If all the other session bean methods we invoke from our bean are also marked REQUIRED, when we invoke them they will join the transaction created for us. This is just fine, since we want the entire ordering action to be covered by a single umbrella transaction. In general, you should use the REQUIRED value if you are modifying any data in your EJB method and you aren t sure whether the client will start a transaction of its own before calling your method. REQUIRES_NEW The REQUIRES_NEW value indicates that the container must always create a new transaction to invoke the EJB method. If the client already has a transaction, it is temporarily suspended until our method returns. This means that the success or failure of our new transaction has no effect on the existing client transaction. From the client s perspective:
1 2 3 4
Its transaction is paused. Our method is invoked. Our method either commits or rolls back its own transaction. The client s transaction is resumed as soon as our method returns.
The REQUIRES_NEW attribute has limited uses in the real world. You should use it if you need a transaction but don t want a rollback to affect the client. Also use this value when you don t want the client s rollback to affect you. Logging is a great example. Even if the parent transaction rolls back, you want to be able to record the failure in your logs. On the other hand, failing to log a minor debugging message should not roll back your entire transaction and the problem should be localized to the logging component. SUPPORTS The SUPPORTS attribute essentially means the EJB method will inherit whatever the transactional environment of the caller is. If the caller does not have a transaction, the EJB method will be called without a transaction. On the other hand, if the
Copyright © OnBarcode.com . All rights reserved.