Most people know object oriented programming and functional programming. But what about aspect oriented programming (AOP)? This repository contains 4 fully working examples of AOP, ranging from standard Spring Aspects to custom Aspects.

• Java JDK 15
• SpringBoot
• Maven

• Use Maven for the build process:

mvn clean install
mvn spring-boot:run

• Find the Swagger-UI API under: http://localhost:8080/swagger-ui.html

• Compute a Fibonacci number:

GET http://localhost:8080/api/fibonacci/40

• Store a String (simulate concurrency issues)

POST http://localhost:8080/api/storeData?data=hello-world

If you compute the 40th Fibonacci number twice, you will see the following log:

Method [fibonacci] gets called with parameters [40]
Execution took [3379ms]
Method [fibonacci] gets called with parameters [40]
Execution took [3ms]

The following aspects are in play:

• @Cacheable: This standard-Spring annotation allows to cache previous results. As you can see above, the first REST call is pretty slow, but the second call is super fast.
• @MonitorTime: We use a custom aspect which measure the total execution time of our REST call and prints the result to the console.
• @LogMethodName: We use a second custom aspect which prints the name and arguments of our REST controller method.

We simulate a dadabase with concurrency issues. Storing a String in our database creates the following log:

Method [storeData] gets called with parameters [hello-world]
Method [storeData] gets called with parameters [hello-world]
Method [storeData] gets called with parameters [hello-world]
Pretend everything went fine

The following aspects are in play:

• @RetryOperation: This Aspect makes sure that the (idempotent) method is retried until it succeeds. In the log above, you can see that it took 3 tries to store the data.