Dinesh on Java

AspectJ @Before Annotation

@Before annotation is not spring annotation, it is aspectj lib annotation so we have add aspectj maven dependency with spring aop in this application. Let’s see below LoggingAspect class with before advice annotation.

/**
 * 
 */
package com.doj.aopapp.aspect;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

/**
 * @author Dinesh.Rajput
 *
 */
@Aspect
@Component
public class LoggingAspect {
 
 /**
  * Declaring before advice 
  * @param jp
  * @throws Throwable
  */
 //@Before("execution(* com.doj.aopapp.service.*.*(..))") // before advice with pointcut expression directly
 @Before("logForAllMethods()") //before advice with named pointcut that declared as name logForAllMethods()
 public void beforeAdviceForAllMethods(JoinPoint jp) throws Throwable {
        System.out.println("****LoggingAspect.beforeAdviceForAllMethods() " + jp.getSignature().getName());
    }
 
 /**
  * Declaring before advice for all transfer methods whose taking three arguments of any type 
  * of all classes in the package com.doj.aopapp.service
  * @param jp
  * @throws Throwable
  */
 @Before("execution(* com.doj.aopapp.service.*.transfer(*,*,*))")
 public void beforeAdviceForTransferMethods(JoinPoint jp) throws Throwable {
        System.out.println("****LoggingAspect.beforeAdviceForTransferMethods() " + jp.getSignature().getName());
    }
 
 /**
  * Declaring named pointcut
  */
 @Pointcut("execution(* com.doj.aopapp.service.*.*(..))")
 public void logForAllMethods(){}
}

Pointcut expressions

1. Following pointcut expression for before advice is valid for all public methods with any arguments of any type and any return type of all classes in the com.doj.aopapp.service package.

@Before("execution(* com.doj.aopapp.service.*.*(..))")

2. Following pointcut expression for before advice is valid for all public methods whose name are transfer() with taking three arguments of any type and any return type of all classes in the com.doj.aopapp.service package.

@Before("execution(* com.doj.aopapp.service.*.transfer(*,*,*))")

Named Pointcut

We can also define pointcut methods for named pointcut. Actually named pointcut is nothing but it is simple way to declaring common pointcut expressions above a method with @Pointcut annotation. This helps to reduce the complexity of writing common complex pointcut expression.

/**
* Declaring named pointcut
 */
@Pointcut("execution(* com.doj.aopapp.service.*.*(..))")
public void logForAllMethods(){}

/**
* before advice with named pointcut that declared as name logForAllMethods()
 */
@Before("logForAllMethods()") //before advice with name pointcut that declared as name logForAllMethods()
public void beforeAdviceForAllMethods(JoinPoint jp) throws Throwable {
       System.out.println("****LoggingAspect.beforeAdviceForAllMethods() " + jp.getSignature().getName());
}

Spring AOP AspectJ @Before Annotation Example

Now let’s see complete example of Spring AOP aspectj @Before annotation.

Spring AOP and AspectJ Maven Dependencies

<properties>
   <spring.version>4.3.7.RELEASE</spring.version>
   <aspectj.version>1.8.9</aspectj.version>
  </properties>
  
  <dependencies>
   <dependency>
         <groupId>org.springframework</groupId>
         <artifactId>spring-context</artifactId>
         <version>${spring.version}</version>
     </dependency>
     <dependency>
         <groupId>org.springframework</groupId>
         <artifactId>spring-context-support</artifactId>
         <version>${spring.version}</version>
     </dependency>
     <dependency>
         <groupId>org.springframework</groupId>
         <artifactId>spring-aop</artifactId>
         <version>${spring.version}</version>
     </dependency>
     
     <dependency>
          <groupId>org.aspectj</groupId>
          <artifactId>aspectjrt</artifactId>
          <version>${aspectj.version}</version>
      </dependency>
      <dependency>
          <groupId>org.aspectj</groupId>
          <artifactId>aspectjweaver</artifactId>
          <version>${aspectj.version}</version>
      </dependency>
  </dependencies>

ApplicationContext Configuration file based on Java Config

AppConfig.java

/**
 * 
 */
package com.doj.aopapp.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

/**
 * @author Dinesh.Rajput
 *
 */
@Configuration
@EnableAspectJAutoProxy
@ComponentScan(basePackages={"com.doj.aopapp.aspect", "com.doj.aopapp.service"})
public class AppConfig {
 
}

@EnableAspectJAutoProxy in Java Configuration:

This spring aop annotation is used to enable @AspectJ support with Java @Configuration add this @EnableAspectJAutoProxy annotation to the application context file.

@Configuration
@EnableAspectJAutoProxy
public class AppConfig {

}

Enabling @AspectJ Support with XML Configuration:

To enable @AspectJ support with XML based configuration use the <aop:aspectj-autoproxy/> element.

<!-- Enable @AspectJ annotation support  -->
    <aop:aspectj-autoproxy />

Target method of Service class on which aspects needs to apply

TransferService.java

/**
 * 
 */
package com.doj.aopapp.service;

/**
 * @author Dinesh.Rajput
 *    
 */
public interface TransferService {
 
 void transfer(String accountA, String accountB, Long amount);
 
 Double checkBalance(String account);
 
 Long withdrawal(String account, Long amount);
 
 void diposite(String account, Long amount);
}

TransferServiceImpl.java

/**
 * 
 */
package com.doj.aopapp.service;

import org.springframework.stereotype.Service;

/**
 * @author Dinesh.Rajput
 *
 */
@Service
public class TransferServiceImpl implements TransferService {

 @Override
 public void transfer(String accountA, String accountB, Long amount) {
  System.out.println(amount+" Amount has been tranfered from "+accountA+" to "+accountB);
 }

 @Override
 public Double checkBalance(String account) {
  return new Double(50000);
 }

 @Override
 public Long withdrawal(String account, Long amount) {
  return amount;
 }

 @Override
 public void diposite(String account, Long amount) {
  System.out.println(amount+" Amount has been diposited to "+account);
 }

}

Aspect class:
LoggingAspect.java as given above in this tutorial.

Test Class for Spring AspectJ Configuration and Execution

Now let’s see how to run and what would be output of this application when above configured aspects execute on given pointcut information.

/**
 * 
 */
package com.doj.aopapp.test;

import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.doj.aopapp.config.AppConfig;
import com.doj.aopapp.service.TransferService;

/**
 * @author Dinesh.Rajput
 *
 */
public class Main {

 /**
  * @param args
  */
 public static void main(String[] args) {
  ConfigurableApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
  TransferService transferService = applicationContext.getBean(TransferService.class);
  transferService.transfer("accountA", "accountB", 50000l);
  System.out.println("Available balance: " +transferService.checkBalance("accountA"));
  transferService.diposite("accountA",  50000l);
  System.out.println("Withdrawal amount: " +transferService.withdrawal("accountB", 40000l));
  applicationContext.close();
 }

}

Output on the Console:

Analyse the output, all join points execute with given information in this example.

Project Structure

Application Source Code

Spring AOP AspectJ @Before Annotation Advice Example on GitHub.