UnitOfWorkProtocol

Overview

The UnitOfWorkProtocol aspect makes the Unit Of Work management transparent in the user code.

It will allow you to write your code like this:

AddressBook book = new AddressBook(...);
book.addContact(contact);

Instead of like this:

UnitOrWork unitOfWork = UnitOfWork.begin();
try {
    AddressBook book = new AddressBook(...);
    unitOfWork.registerNew(book); 
    book.addContact(contact);
    unitOfWork.registerDirty(book); 
    unitOfWork.commit();
} 
catch(Exception e) {
    unitOfWork.rollback();  
}
finally {
    unitOfWork.dispose();
}

and still all the transaction and persistence management will take place.

Definition

The UnitOfWorkProtocol aspect has abstract pointcuts that you have to define in your aop.xml file (a "transactional object" is an object that is set to participate in the Unit Of Work transaction, meaning that the Unit Of Work will keep track of its state):

• txRequires - picks out all points in the code where you want a TX REQUIRES transaction to begin, commit and rollback
• txRequiresNew - picks out all points in the code where you want a TX REQUIRES_NEW transaction to begin, commit and rollback
• txSupports - picks out all points in the code where you want a TX SUPPORTS transaction to begin, commit and rollback
• txMandatory - picks out all points in the code where you want a TX MANDATORY transaction to begin, commit and rollback
• txNever - picks out all points in the code where you want a TX NEVER transaction to begin, commit and rollback
• transactionalObjects - picks out all transactional object, this pointcut is used by the Transactional Mixin
• transactionalObjectCreationPoints - picks out all points in the code where a transactional object is created
• transactionalObjectModificationPoints - picks out all points in the code where a transactional object is being modified (best done with a set(...) pointcut)

Here is an example on how to define this in XML:

<aspect class="org.codehaus.aware.unitofwork.UnitOfWorkProtocol">
    <pointcut name="txSupports" expression="execution(* org.codehaus.aware.app.service.*.*(..))"/>
    <pointcut name="txRequires" expression="execution(* org.codehaus.aware.app.domain.*.*(..))"/>

    <pointcut name="transactionalObjects" expression="within(org.codehaus.aware.app.domain.*)"/>
    <pointcut name="transactionalObjectCreationPoints" expression="call(org.codehaus.aware.app.domain.*.new(..))"/>
    <pointcut name="transactionalObjectModificationPoints" expression="set(* org.codehaus.aware.app.domain.*.*)"/>
</aspect>