Cross Cutting

:"For other uses, see Cross cut."

Cross cutting

Even though most classes in an object-oriented programming model will perform a single, specific function, they often share common, secondary requirements with other classes. These secondary requirements are said to cross-cut into the primary requirements.

For example, a typical application comprises cross cutting concerns like logging within the data access layer and also in the user interface layer whenever a thread enters or exits a method. Even though the primary functionality of each class is very different, the code needed to perform the secondary functionality, in this case, logging, is often identical.

Example code

public class SomeBusinessClass extends OtherBusinessClass { // Core data members // Other data members: Log stream, data-consistency flag // Override methods in the base class public void performSomeOperation(SomeOperationInformation info) { // Ensure authentication // Ensure info satisfies contracts // Lock the object to ensure data-consistency in case other // threads access it // Ensure the cache is up to date // Log the start of operation // = Perform the core operation =

// // // // = End performing the core operation =

// Log the completion of operation // Unlock the object } // More operations similar to above public void save(PersitanceStorage ps) { } public void load(PersitanceStorage ps) { } }

In the code above, we must consider at least three issues:
# Other data members do not belong to this class's core concern.
# Implementation of performSomeOperation() seems to do more than perform the core operation; it seems to handle the peripheral data logging, authentication, multithread safety, contract validation, and cache management concerns. In addition, many of these peripheral concerns would likewise apply to other classes.
# It is not clear if save() and load() performing persistence management should form the core part of the class.

See also

*Aspect
*AspectJ
*Aspect-oriented programming
*Pointcut

External links

* [http://eclipse.org/aspectj AspectJ Home Page]
* [http://eclipse.org/ajdt AJDT Home Page]
* [http://aosd.net AspectOriented Software Development HomePage]