Introducing Spring Framework

Chapter 8 ■ Give Advice to Your Spring Application
AOP Concepts
Let’s quickly review some of the AOP concepts over your SearchEngineService.java class (as shown in Listing 8-1).
Let’s also start thinking about the logging concerns (see Figure 8-2 and Table 8-1). Start by writing your concerns.
Figure 8-2. AOP Definitions
Table 8-1. AOP Concepts
ASPECT
ADVICE
POINTCUT
JOIN POINT
A set of pointcuts and related advices.
An action that will be executed at the join points in a particular pointcut.
A pattern (expression language) that bounds an advice with a single or many joint points.
A method exception where the advice will be executed.
Figure 8-2 explains the Table 8-1 concepts that you will find within your Log module. But I’ll explain them more
in detail here. In your case, you need to create a Log module that will log every method call you have. Figure 8-2 shows
the Log module that will define an advice.
Figure 8-2 shows how the aspect will be applied. So in this case, the Log module defines an advice, this advice
will be executed based on the defined pointcut. Figure 8-2 shows the (* findBy*(*)) pointcut expression. This
expression means the following:
• Select a method that has any return type (* findBy*(*)), that is what the first asterisk means.
• Select a method that contains a prefix findBy. (* findBy*(*)).
• With any number of parameters (* findBy*(*)), that is what the last asterisk means.
So based on the preceding explanation, then joint point will be the findByType(Type Document)method that
will execute the advice. In other words, the method findByType will be intercepted and the Log module logic will be
executed. All of this working together is an aspect.
The Spring Framework provides an AOP extension and supports four types of advices:
• Before advice: Runs before every method call.
• After returning advice: Runs after a method call and returns a result.
• Around advice: Runs before and after a method call, and combines advices.
• After throwing advice: Runs after throwing an exception.
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