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项目作者： deecarneiro

项目描述 ：
AspectJ practices from AOP practical classes.
高级语言： AspectJ
项目地址: git://github.com/deecarneiro/AOP.git
创建时间： 2021-02-27T14:30:39Z
项目社区：https://github.com/deecarneiro/AOP
开源协议：
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AOP

A simple introduction to Aspect Oriented Programming with AspectJ.

What’s AOP?

AOP (aspect-oriented programming) is a programming style that can be adopted to define certain policies that in turn are used to define and manage the cross-cutting concerns in an application. In essence, it’s a programming paradigm that enables your application to be adaptable to changes.

Libs/Frameworks

  • AspectJ: an aspect-oriented programming (AOP) extension created at PARC for the Java programming language. It is available in Eclipse Foundation open-source projects, both stand-alone and integrated into Eclipse. AspectJ has become a widely used de facto standard for AOP by emphasizing simplicity and usability for end users. It uses Java-like syntax, and included IDE integrations for displaying crosscutting structure since its initial public release in 2001.

Code Snippet

Hello World

  • Class Exe01, print World on screen
  1.     public class Exe01 {
  2.          public static void printHelloWorld(){
  3.                 System.out.print(" World");
  4.             }
  6.             public static void main(String[] args){
  7.                 Exe01.printHelloWorld();
  8.             }
  10.     }
  • AspectJ class with pointcuts and advices that will be applied on function printHelloWorld()
  1. public aspect Exe01Aspect {
  3.       pointcut nome(): execution (* Exe01.printHelloWorld());
  5.         before() : nome() {
  6.             System.out.print("Hello");
  7.         }
  9.         void around() : nome(){
  10.             //proceed(); Advice is executed after pointcut 
  11.             System.out.print(" Nobody!"); //without proceed method, advice replaces pointcut 
  12.             // proceed(); Advice is executed before pointcut
  13.         }
  15.         after() : nome(){
  16.             System.out.print(", DeeCarneiro!!");
  17.         }
  18. }

Pointcuts

They allow a programmer to specify join points (well-defined moments in the execution of a program, like method call, object instantiation, or variable access). All pointcuts are expressions (quantifications) that determine whether a given join point matches. For example, this point-cut matches the execution of printHelloWorld() method in an object of type Exe01:

  1.       pointcut nome(): execution (* Exe01.printHelloWorld());

Advices

They allow a programmer to specify code to run at a join point matched by a pointcut. The actions can be performed before, after, or around the specified join point. Here, the advice print on the screen a string after printHelloWorld() method execution:

  1.        after() : nome(){
  2.             System.out.print(", DeeCarneiro!!");
  3.         }

More examples

  1.     //Intercepts the execution of the method Solve with int type parameter
  2.     public pointcut point01() : execution ( void PointcutExample.Solve(int));
  4.     //Intercepts the calling of the constructor of the PointcutExample
  5.     public pointcut point02() : call (PointcutExample.new());
  7.     //Intercepts the calling of the constructor of the PointcutExample with parameters
  8.     public pointcut point03() : call (PointcutExample.new(String, int));
  10.     //Intercepts the getting of the diff attribute from PointExample class
  11.     public pointcut point04() : get (* PointcutExample.diff);
  13.     //Intercepts the setting of any attribute from PointExample class
  14.     public pointcut point05() : set( * PointcutExample.*);
  16.     //Intercepts the calling of any method with int type parameter from PointExample class
  17.     public pointcut point06() : call ( * PointcutExample.*(int));
  19.     //Intercepts the calling of any method that starts with S on any part of system
  20.     public pointcut point07() : call (* *.S*(..));
  22.     //Intercepts the execution of any method from PointcutExample method
  23.     public pointcut point08() : execution (* PointcutExample.*(..));
  25.     //Intercepts the handler of any method within code PointExample.
  26.     public pointcut point09() : handler (Exception) && withincode(* PointcutExample.*(..) );

Runnig

AspectJ Project Eclipse

In Eclipse IDE install AspectJ:

— Help > Eclipse Marketplace and search for AspectJ

— Install AspectJ