Adrian Alonso

In this post I wish to show how the combination of annotations and AOP can be used to perform a "parameter cannot be null" validation in a class' method.

Suppose we have the following method that is executed only if the parameter value is not null:

One possibility is to include the same code if (copy paste the same code pattern) in all methods that need this behavior. Another one ( much more elegant ) is design a solution based on AOP and Annotations. Let’s start by defining the NotNullParameter annotation as following:

The preceding code is read as simple as “Intercept all the execution of any method of any package or sub package of ar.adalon that accept one parameter (of type or subtype of object… hence is any instance) and is decorated with the @NotNullParameter annotation”. The around advise allows to continue (procced) or terminate (return;) with the intercepted method’s execution. Now, we can simplify our service to:

By this way, I intended to show you how AOP crosscutting allow to break up the business logic and additional validations .

Labels: Java

# posted by Adrian Alonso : 10:08 AM