Rating of Open Source AOP Frameworks in .NET

Introduction

In the days where business agility is becoming the definite need of any business / IT infrastructure, quite frequently we are ending up with facing scenarios where we need to develop applications that are flexible and easily manageable.

The flexibility in an application’s architecture is demanded by the emerging business competitions, pressure to sustain the challenges created by the innovative business models, need to sustain the growing customer’s base of an established business, etc. Say for example you are building an e-commerce system with an innovative business model, targeting a niche market. Soon, it is becoming hot in the market and your system is witnessing a rapidly growing user base, in a short span of time. The system starts crawling, failing to sustain the increased user load there by creating significant loss to your business and to the goodwill you have created with your hard work and innovation.

Situations that may pull your business down may be like:

• Changes in the regulations / policies of the government because of which you may need to incorporate some more rules into your system, while keeping it running
• Need to switch from your payment gateway to another one who is offering services at a discounted price, to increase the revenue
• Need to shift from one packaging company to other (like say from FedEx to UPS) as there is a need to increase of the speed of the delivery
• Demand to shift from a particular financial outsourcing services provider to another
• Etc.

The architecture that could excel in such an agile environment can be called “Pluggable Architecture”. There are proven methodologies (Patterns) that can constitute the design to realize such architectures. AOP is one of such available patterns / methodologies widely adopted in the market.

Background

AOP – Aspect Oriented Programming is a methodology that helps in keeping the “cross-cutting concerns” separate from the code blocks that encapsulate business logic. “Cross-cutting” here refers to the code blocks that are non-business specific and that are repeated across different classes spread across different layers. Examples of cross cutting concerns are: Logging, Exception Handling code blocks specific to instrumentation of the code, etc. There may be many numbers of such concerns which need to be abstracted from the business logic specific code.

The basic thumb rule to identify a cross-cutting concern is: If a concern is repeated across classes spread over layers / tiers, then it is a cross-cutting concern.

AOP Benefits

The facility to separate the cross-cutting concerns helps in:

1. Selectively applying the cross cutting concerns, as required. Say some logic related to profiling the code for performance monitoring would be required only at the time of testing but not in the production environment so they can be enabled/disabled based on the environment as required.
2. Applying any changes / fixing bugs in the cross-cutting code logic, without affecting the business logic code in the production environment.
3. Evolution of the different parts of the system in different paces.
4. Arriving at a final solution where the code is easy to understand and maintain

Need for a Rating Methodology

Having realizing the benefits of AOP, the next step is to look for ways to implement it in our application development. In this case, instead of starting from scratch, the best way is to leverage the research and effort put by many hardworking tech savvies around the world through the availability of open source frameworks / utilities.

When we are in the stage of looking for adopting an open source AOP framework, lots of open source AOP frameworks are available in the market and hence, we need to choose the best possible one for our development. Choosing the best possible one could be a difficult task as always there will be conflicts of thoughts and difference of opinions, especially when we are in a team. Especially when we are in a position to convince our customers for the adoption of a particular framework, we cannot choose a particular AOP framework, unless we have some good justifications.

Will it not be good, if we have rating methodology where we can analyze and evaluate the available AOP frameworks qualitatively and quantitatively enabling us to rate the AOP frameworks in the market so that we can make an informed decision in a short span of time. The result of such a thought process is the following “Frameworks Rating Methodology”.

Open Source AOP Frameworks Rating Methodology

As a part of this effort, I had identified some of the attributes (which can be expanded / refined) and assigned points for each of the AOP frameworks (which is subjective – It is based on my research and information available to me. You can change it as per your observation and conviction.)

The list of the open source AOP frameworks that are considered for this rating process are:

• Aspect#
• AspectDng
• NAspect
• PostSharp
• Policy Injection Application Block
• Sesar
• Spring.NET [Spring.AOP]

The Rating attributes identified and used for this rating process are:

I have assigned very low points if the information is not clear or if it is not available or if it is vague.

Guidance for Rating Attributes

• 0 – bad, Not known, Not clear, sufficient information not available
• 1 – To be improved, some information is available
• 2 – Good, sufficient information is available
• 3 – Very good, no major overhead, no major memory footprint, excellent information is available

Here is the resulting rating matrix:

Conclusion

Whenever we go for implementing a particular methodology or concept like AOP, we will always leverage the existing open source frameworks. Since there are a number of open source frameworks available in the market, it will always be good to have some concrete justifications as a base for selecting a particular framework for adoption.

Adopting a rating process like the one explained in this article will ensure that the frameworks are subjected to both qualitative & quantitative evaluation process, resulting in a meaningful decision.

From the matrix, the frameworks that emerged in the ‘top 3 ‘list of are:

• PostSharp
• Policy Injection Application Block
• Spring.Net [Spring.AOP]