Aspect Oriented Programming – Transaction Management

29 Pages·2006·0.57 MB·English

by  Lorenzo Clementi

Aspect Oriented Programming – Transaction Management
Presentation outline
● Transaction management: why?
A simple banking system – Example
● Existing solutions – without AOP
Enterprise JavaBeans (JTA)
Transaction Support for the bankning example – the conventional solution
● Basic AOP transaction management
An AOP solution for the banking example
● Improved AOP transaction management
AOP desing patterns
● Conclusion

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Aspect Oriented Programming – Transaction Management
Presentation outline
● Transaction management: why?
A simple banking system – Example
● Existing solutions – without AOP
Enterprise JavaBeans (JTA)
Transaction Support for the bankning example – the conventional solution
● Basic AOP transaction management
An AOP solution for the banking example
● Improved AOP transaction management
AOP desing patterns
● Conclusion

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Aspect Oriented Programming – Transaction Management
Transaction – ACID properties
A transaction is a set of operations respecting the ACID properties.
ACID stands for:
Atomicity
Consistency
Isolation
Durability
The most important feature is atomicity: the transaction is committed only if all its updates complete
successfully. Otherwise, it is rolled back.

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Aspect Oriented Programming – Transaction Management
A simple banking system structure
Let's introduce the example of a simple banking system.
nested transaction

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Aspect Oriented Programming – Transaction Management
Nested transaction
The method transfer contains a nested transaction:
   public static void transfer(Account from, Account to, float amount)
throws InsufficientBalanceException {
to.credit(amount);
from.debit(amount);
}
Both credit and debit perform a database update.

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Aspect Oriented Programming – Transaction Management
Why are transactions important?
Imagine we want to execute the following operations:
public static void main(String[] args) throws Exception {
Account account1 = new AccountJDBCImpl(1);
Account account2 = new AccountJDBCImpl(2);
account1.credit(300);
account1.debit(200);
InterAccountTransferSystem.transfer(account1, account2, 100);
InterAccountTransferSystem.transfer(account1, account2, 100);
}
The last operation fails and the database is left in an inconsistent state.

Example 1

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Aspect Oriented Programming – Transaction Management
Presentation outline
● Transaction management: why?
A simple banking system – Example
● Existing solutions – without AOP
Enterprise JavaBeans (JTA)
Transaction Support for the bankning example – the conventional solution
● Basic AOP transaction management
An AOP solution for the banking example
● Improved AOP transaction management
AOP desing patterns
● Conclusion

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Aspect Oriented Programming – Transaction Management
Existing transaction management solutions
Several companies offer transaction management systems (try to type transaction management in
Google).
We are going to look closer at how transaction management is handled in the “Java world”.
● JDBC (Java DataBase Connectivity)
● J2EE and JTA (Java Transaction API)

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Aspect Oriented Programming – Transaction Management
EJB Server and Java Transaction API (JTA)
Let's look at the structure of an EJB server:
● The EJB Components implement the program business logic.
● The EJB Container makes several services available to the Components. One of these
services is transaction management.

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Aspect Oriented Programming – Transaction Management
JTA transactions
JTA is able to perform transactions over several data sources at the same time. JTA manages all the
low level details.
A JTA transaction can be demarcated in two different ways:
● Programmatic demarcation: the transaction is hardcoded. This is not much different from a
JDBC transaction.
● Declarative demarcation: an xml configuration file defines for each method (or class), what
kind of transaction action has to be carried out. The EJB Component methods do not contain
transaction code anymore.

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