Observe extra behaviour around an existing product service without mixing it into the business operation.
Open this stage in the online learning path
Use JDK 21 or newer and Maven 3.9 or newer. Verify with java -version and mvn -version. Extract this project into its own folder; do not merge its files with another stage.
This lesson reuses the product catalog and Todo responsibilities from Stages 8–14. Only the feature described below is new. Read the ordered explanation before opening the complete files.
ProductService.count returns the product count. The aspect contains the additional logging concern; the service does not call the aspect itself.
@EnableAspectJAutoProxy installs Spring’s annotation-driven AOP support. We request class-based proxies to keep the concrete service lookup simple. AspectJ annotations and pointcut expressions are used with Spring runtime proxies, not AspectJ bytecode weaving.
The service method execution is the join point. The pointcut selects executions. The advice is the extra method that runs. The aspect groups these rules. In Spring AOP, interception applies to method execution through eligible managed proxies, not arbitrary source-code lines.
@Before runs before the selected method. @After means finally-style advice: it runs after normal return or exception. @AfterReturning is different and runs only after successful completion. The result is printed after the proxied method returns.
Open a terminal in the extracted folder containing pom.xml. Run one command at a time.
mvn test
mvn spring-boot:runThis is a console lesson. It does not open a web port. Application.main starts a Spring context, calls the demonstration and closes the context. Read the terminal, not a browser. Spring Boot’s Maven plugin is used as a convenient launcher; these examples show Spring Framework directly.
Before: count
Service body
After (finally)
Result: 2Object identifiers and elapsed times can vary. Compare the relationship between values rather than copying an identifier.
Create the following files at exactly these paths, or use the ZIP. Source files include their imports. The test checks the behaviour described in the lesson.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>4.1.1</version><relativePath/></parent>
<groupId>com.edupoly</groupId><artifactId>spring-stage-31-aop-advice</artifactId><version>1.0.0</version>
<properties><java.version>21</java.version></properties>
<dependencies>
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency>
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency>
<dependency><groupId>org.springframework</groupId><artifactId>spring-aop</artifactId></dependency>
<dependency><groupId>org.aspectj</groupId><artifactId>aspectjweaver</artifactId></dependency>
</dependencies>
<build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build>
</project>
package com.edupoly.lesson;
import org.springframework.context.annotation.*;
@Configuration @ComponentScan("com.edupoly.lesson") @EnableAspectJAutoProxy(proxyTargetClass = true)
public class AppConfig { }
package com.edupoly.lesson;
import org.springframework.stereotype.Service;
@Service public class ProductService {
public int count() { System.out.println("Service body"); return 2; }
}
package com.edupoly.lesson;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;
@Aspect @Component public class LoggingAspect {
@Pointcut("execution(* com.edupoly.lesson.ProductService.count(..))")
public void productOperation() { }
@Before("productOperation()") public void before(JoinPoint point) { System.out.println("Before: " + point.getSignature().getName()); }
@After("productOperation()") public void after() { System.out.println("After (finally)"); }
}
package com.edupoly.lesson;
import org.springframework.stereotype.Component;
@Component public class Lesson {
private final ProductService service;
public Lesson(ProductService service) { this.service = service; }
public void run() { System.out.println("Result: " + service.count()); }
}
package com.edupoly.lesson;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Application {
public static void main(String[] args) throws Exception {
try (var context = new AnnotationConfigApplicationContext(AppConfig.class)) {
context.getBean(Lesson.class).run();
}
}
}
package com.edupoly.lesson;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
class LessonTest {
@Test void advicePreservesReturnValueAndUsesProxy() {
try (var context = new AnnotationConfigApplicationContext(AppConfig.class)) {
var service = context.getBean(ProductService.class);
assertTrue(org.springframework.aop.support.AopUtils.isAopProxy(service));
assertEquals(2, service.count());
}
}
}
Remove @EnableAspectJAutoProxy. The beans still exist but their aspect advice no longer runs. Restore it.
| Word | Meaning in this example |
|---|---|
| Aspect | A bean defining advice and the operations it applies to. |
| Pointcut | A rule selecting method executions. |
| Advice | Additional behaviour before, after or around an invocation. |
Add another service method. Predict whether the current pointcut matches it, then run the example to check. Keep the service return value unchanged.