As mentioned before, pointcuts are used to define a point where advice would be applied. So pointcut is one of the most important elements of an aspect in the application. Let's understand how to define pointcuts. In Spring AOP, we can use expression language to define the pointcuts. Spring AOP uses AspectJ's pointcut expression language for selecting where to apply advice. Spring AOP supports a subset of the pointcut designators available in AspectJ because as you know, Spring AOP is proxy-based and some designators do not support proxy-based AOP. Let's see following table has Spring AOP supported designators.
|
Spring supported AspectJ designators |
Description |
|
execution |
It matches the join points by method executions, it is primary pointcut designator supported by Spring AOP. |
|
within |
It matches the join points by limit within certain types. |
|
this |
It limits matching to join points where the bean reference is an instance of the given type. |
|
target |
It limits matching to join points where the target object is of a given type. |
|
args |
It limits matching to join points where the arguments are instances of the given types. |
|
@target |
It limits matching to join points where the target object has an annotation of the given type. |
|
@args |
It limits matching to join points where the runtime, type of the actual arguments passed have annotations of the given type. |
|
@within |
It limits matching to join points where the declared type of the target object has the given type annotation. |
|
@annotation |
It limits matching to join points where the subject of the join point has the given annotation. |
As listed earlier, Spring supported pointcut designators, execution is primary pointcut designator. So here I will only show you how to define pointcuts using execution designators. Let's see how to write the pointcut expression in the application.