Custom Annotation To Handle Authorisation In Spring Boot AOP Tutorial

Overview:

• Creating custom annotation
• Creating component in spring boot
• Creation a configuration and middleware in spring boot
• Basic of Aspect and usage in spring boot

What is Aspect In Spring Boot ?

Aspects are cross cutting concerns like logging,security in different layers for the ease of code maintenance .

Key Dependency required

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-aop</artifactId>
  <version>5.0.1.RELEASE</version>
  <scope>compile</scope>
</dependency>
<dependency>
  <groupId>org.aspectj</groupId>
  <artifactId>aspectjweaver</artifactId>
  <version>1.8.12</version>
  <scope>compile</scope>
</dependency>

• Spring AOP provides basic AOP Capabilities.
• AspectJ provides a complete AOP framework.

• STEP 1 : Lets create an annotation

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD) // can use in method only.
public @interface Authorized {

  public boolean enabled() default true;

}

@Retention(RetentionPolicy.RUNTIME) : instruct compiler to retain the annotation during runtime
@Target(ElementType.METHOD) : this suggest where this annotation can be used

• Step 2 : Lets Create a file which actually implement logic of authorization

@Component
public class AuthorizationImpl { 
    
    public boolean authorize(String token) {
        // implemnt jwt or any any token based authorization logic
        return true;
    }
}

• Step 3 Aspect file which acts as middleware which intercept the the request and authorize and proceed

@Aspect
@Configuration
public class AuthAspect {
@Autowired
   AuthorizationImpl authBean;
   
   @Before("@annotation(com.<packagepath>.Authorized) && args(request,..)")
   public static void before(HttpServletRequest request){
       if (!(request instanceof HttpServletRequest)) {
           throw 
           new RuntimeException("request should be HttpServletRequesttype");
       }
       
       if(authBean.authorize(request.getHeadr("Authorization"))){
           req.setAttribute(
           "userSession", 
           "session information which cann be acces in controller"
           );
       }else {
            throw new RuntimeException("auth error..!!!");
       }
      
   } 
   
}

• Step 3 : Usage of the annotation to authorize the request

@RestController
@RequestMapping(path = "/activities-to-jobs",
        produces = {APPLICATION_JSON_VALUE},
        headers = {"Authorization"})
public class XxxxController {
   @RequestMapping(path = "/{id}/note", method = RequestMethod.GET)
   @Authorized
   public opDTO getSomeResult(HttpServletRequest request,....){
   
   }
}