Spring AOP AspectJ @Before Annotation Example

In this spring aop example, we will learn to use aspectj @Before annotation. @Before annotated methods run exactly before the all methods matching with pointcut expression.

In this example, We will create simple spring application, add logging aspect and then invoke aspect methods based on pointcuts information passed in @Before annotation.

AspectJ @Before Annotation Usage

You can use @Before annotation in below manner.

@Aspect
public class LoggingAspect {

    @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.*(..))")
    public void logBeforeAllMethods(JoinPoint joinPoint) { ... }

    @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.getEmployeeById(..))")
    public void logBeforeGetEmployee(JoinPoint joinPoint) { ... }
}

Project Structure

Spring AOP AspectJ Maven Dependencies

I have added spring core, spring aop and aspectj dependencies.

<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>
    <groupId>com.howtodoinjava</groupId>
    <artifactId>SpringAOPExamples</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Spring AOP Examples</name>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.8.9</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.9</version>
        </dependency>
    </dependencies>
</project>

Enable AspectJ Support

In XML config file, you can add aop:aspectj-autoproxy element to enable @AspectJ annotation support.

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/aop/
    http://www.springframework.org/schema/aop/spring-aop-3.0.xsd ">

    <!-- Enable @AspectJ annotation support  -->
    <aop:aspectj-autoproxy />
    
    <!-- Employee manager -->
    <bean id="employeeManager" class="com.howtodoinjava.app.service.impl.EmployeeManagerImpl" />

    <!-- Logging Aspect -->
    <bean id="loggingAspect" class="com.howtodoinjava.app.aspect.LoggingAspect" />

</beans>

Service methods on which aspects needs to be executed

EmployeeManager.java and EmployeeManagerImpl.java

public interface EmployeeManager 
{
    public EmployeeDTO getEmployeeById(Integer employeeId);

    public List<EmployeeDTO> getAllEmployee();

    public void createEmployee(EmployeeDTO employee);

    public void deleteEmployee(Integer employeeId);

    public void updateEmployee(EmployeeDTO employee);
}

public class EmployeeManagerImpl implements EmployeeManager 
{
    public EmployeeDTO getEmployeeById(Integer employeeId) 
    {
        System.out.println("Method getEmployeeById() called");
        return new EmployeeDTO();
    }

    public List<EmployeeDTO> getAllEmployee() 
    {
        System.out.println("Method getAllEmployee() called");
        return new ArrayList<EmployeeDTO>();
    }

    public void createEmployee(EmployeeDTO employee)
    {
        System.out.println("Method createEmployee() called");
    }

    public void deleteEmployee(Integer employeeId) 
    {
        System.out.println("Method deleteEmployee() called");
    }

    public void updateEmployee(EmployeeDTO employee) 
    {
        System.out.println("Method updateEmployee() called");
    }
}

Write AspectJ Annotated Class and Methods

Write aspectj annotated class and methods with pointcut information.

@Aspect
public class LoggingAspect {
    
    @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.*(..))")
    public void logBeforeAllMethods(JoinPoint joinPoint) 
    {
        System.out.println("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName());
    }
    
    @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.getEmployeeById(..))")
    public void logBeforeGetEmployee(JoinPoint joinPoint) 
    {
        System.out.println("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName());
    }
    
    @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.createEmployee(..))")
    public void logBeforeCreateEmployee(JoinPoint joinPoint) 
    {
        System.out.println("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName());
    }
}

Test Spring AspectJ Configuration and Execution

Now let’s test whether above configured aspects execute on given pointcut information.

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.howtodoinjava.app.model.EmployeeDTO;
import com.howtodoinjava.app.service.EmployeeManager;

public class TestMain 
{
    @SuppressWarnings("resource")
    public static void main(String[] args) {
 
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        EmployeeManager manager = (EmployeeManager) context.getBean("employeeManager");
 
        manager.getEmployeeById(1);
        manager.createEmployee(new EmployeeDTO());
    }
}

****LoggingAspect.logBeforeAllMethods() : getEmployeeById
****LoggingAspect.logBeforeGetEmployee() : getEmployeeById

Method getEmployeeById() called

****LoggingAspect.logBeforeAllMethods() : createEmployee
****LoggingAspect.logBeforeCreateEmployee() : createEmployee

Method createEmployee() called

Clearly aspect advices executed on revelant jointpoints.

Happy Learning !!

References:

Spring AOP Reference
@Before Annotation
@Aspect Annotation
AspectJ Annotation Config Example
Different Pointcut Expressions With Examples