Spring AOP with annotations

Spring AOP allows us to add multiple aspects without changing the actual business logic code of java files like controllers, service etc.

In this example, I am going to explain you how to apply aspects in a spring based application using annotations.

I am adding these examples on top of the existing spring application that is explained in below articles.

• Spring Web Application using MVC and annotations without web.xml

• How to add spring interceptors using annotations

Step 1: Add @EnableAspectJAutoProxy annotation to the spring configuration file.

SpringWebConfig

package com.kswaughs.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;

import com.kswaughs.interceptor.TransactionInterceptor;

@EnableAspectJAutoProxy
@EnableWebMvc 
@Configuration
@ComponentScan({ "com.kswaughs.web" })
public class SpringWebConfig extends WebMvcConfigurerAdapter {
 
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/resources/**").addResourceLocations("/resources/");
    }
 
    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setViewClass(JstlView.class);
        viewResolver.setPrefix("/jsps/");
        viewResolver.setSuffix(".jsp");
        return viewResolver;
    }
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
  
        registry.addInterceptor(new TransactionInterceptor())
                .addPathPatterns("/**")
                .excludePathPatterns("/phones");
    }
}

Step 2: Create an Aspect class and define the pointcut expression where you want to apply this aspect. In this example, I am applying this aspect after PhoneService.getPhoneDetails() method is executed.

PhoneLogAspect

package com.kswaughs.web.aspect;

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

@Aspect
@Component
public class PhoneLogAspect {

    @AfterReturning(
        pointcut = "execution(* com.kswaughs.web.service.PhoneService.getPhoneDetails(..))",
        returning = "result")
    public void logAfterReturning(JoinPoint joinPoint, Object result) {

        System.out.println("******");
        System.out.println("logAfterReturning() is running!");
        System.out.println("Method Intercepted : " + joinPoint.getSignature().getName());
        System.out.println("Method returned value is : " + result);
        System.out.println("******");
    }
}

Below is the output printed in console when phone details page is rendered to the browser.

output:
******
logAfterReturning() is running!
Method Intercepted : getPhoneDetails
Method returned value is : Phone [id=2, name=Nokia Lumia, price=12,000]
******

Maven dependencies

pom.xml

<dependencies>
    <!-- Spring framework -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <!-- AspectJ -->
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>1.6.11</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.7.2</version>
    </dependency>
    <!-- JSTL for jsp pages -->
        <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
    <!-- Servlet API jars -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>servlet-api</artifactId>
        <version>2.5</version>
        <scope>provided</scope>
    </dependency>
</dependencies>