How to get a method's annotation value from a ProceedingJoinPoint?

Question

I have below annotation.

MyAnnotation.java

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {

}

SomeAspect.java

public class SomeAspect{

 @Around("execution(public * *(..)) && @annotation(com.mycompany.MyAnnotation)")
    public Object procede(ProceedingJoinPoint call) throws Throwable {

  //Some logic

}

}

SomeOther.java

public class SomeOther{

@MyAnnotation("ABC") 
public String someMethod(String name){


}


}

In above class am passing "ABC" with in @MyAnnotation. Now how can i access "ABC" value in procede method of SomeAspect.java class?

Thanks!

Answer 1

You can get the Signature from a ProceedingJoinPoint and in case of a method invocation just cast it to a MethodSignature.

@Around("execution(public * *(..)) && @annotation(com.mycompany.MyAnnotation)")
public Object procede(ProceedingJoinPoint call) throws Throwable {
    MethodSignature signature = (MethodSignature) call.getSignature();
    Method method = signature.getMethod();

    MyAnnotation myAnnotation = method.getAnnotation(MyAnnotation.class);
}

But you should first add an annotation attribute. Your example code doesn't have one, e.g.

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {

    String value();
}

Then you can access it

MyAnnotation myAnnotation = method.getAnnotation(MyAnnotation.class);
String value = myAnnotation.value();

EDIT

How to get value if I have @MyAnnotation("ABC") at class level ?

A Class is also an AnnotatedElement, so you can get it the same way as from a Method. E.g. An annotation of the method's declaring class can be obtained using

 Method method = ...;
 Class<?> declaringClass = method.getDeclaringClass();
 MyAnnotation myAnnotation = declaringClass.getAnnotation(MyAnnotation.class)

Since you are using spring you might also want to use spring's AnnotationUtils.findAnnotation(..). It searches for an annotation as spring does. E.g. also looking at superclass and interface methods, etc.

 MyAnnotation foundAnnotation = AnnotationUtils.findAnnotation(method, MyAnnotation.class);

EDIT

You might also be interessted in the capabilities of spring's MergedAnnotations which was introduced in 5.2.

Answer 2

Actually I think we can get the value in another way round instead of just from ProceedingJoinPoint, which will definitely require us to make use of reflection.

Have a try as follows using annotation directly: add com.mycompany.MyAnnotation yourAnnotation in your advice params and @annotation(yourAnnotation) in @Around.

@Around("execution(public * *(..)) && @annotation(yourAnnotation)")
public Object procede(ProceedingJoinPoint pjp, com.mycompany.MyAnnotation yourAnnotation) {
    ...
    yourAnnotation.value(); // get your annotation value directly;
    ...
}

com.mycompany.MyAnnotation in advice params just work as that in

@Around("execution(public * *(..)) && @annotation(com.mycompany.MyAnnotation)")

yourAnnotation can be valid variable name since MyAnnotation in params already points out which annotation it should be. Here yourAnnotation is used to retrieve the annotation instance only.

If you want to pass more params you can try args().

For more details, do please check its official doc. For Annotation value, you can just search @Auditable.

Answer 3

This works as well - You can fetch annotation information using reflection on the class.

Annotation anno = MyClass.class.getAnnotation(MyAnnotation.class);

Or

Annotation anno = MyClass.class.getDeclaredMethod("somethod").getAnnotation(MyAnnotation.class);

This works only if your annotation is available at runtime, which you have declared correctly.

@Retention(RetentionPolicy.RUNTIME)

Answer 4

René's example is taking me a long way. Also the explanation how I get ClassLevel Annotations.

But then I can only read ClassLevel Annotations Values if I have previously used a method annotation with "*@Around("execution(public * (..)) && @annotation(com.mycompany.MyAnnotation)")""

How can I get around this? How can I trigger an Aspect if a ClassLevel Annotation is set without going through a Method Execution?

I want to write a ClassLevel Annotation like

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(value = { ElementType.METHOD, ElementType.TYPE })
@EnableSwagger2
@Import(SwaggerConfiguration.class)
public @interface EnableSwaggerApi {
    String controllerPackage() default "foo.bar.ctrl";
}

It's importing the Configuration about "SwaggerConfiguration" where I want to receive the value of "controllerPackage"

@Aspect
public class SwaggerConfiguration {

    @Value("${tom.swagger.controller.package:foo.bar.notset}")
    private String  controllerPackage;

    @Value("${tom.swagger.api.version:1.0.0}")
    private String  apiVersion;

    @Value("${spring.application.name:MyApplication}")
    private String  applicationName;

    @Around("execution(public * *(..)) && @annotation(EnableSwaggerApi)")
    public void procede(ProceedingJoinPoint call) throws Throwable {
        MethodSignature signature = (MethodSignature) call.getSignature();
        Method method = signature.getMethod();

        Class<?> declaringClass = method.getDeclaringClass();
        EnableSwaggerApi myAnnotation = declaringClass.getAnnotation(EnableSwaggerApi.class);
        System.err.println("1 -> " + myAnnotation.controllerPackage());  // -> tko.backend.spring.ctrl

        myAnnotation = method.getAnnotation(EnableSwaggerApi.class);
        System.err.println("2 -> " + myAnnotation.controllerPackage()); // -> tko.backend.spring.SOMEOTHERSTUFF


        // THIS WORKS, BUT JUST IF I USE THE @EnableSwaggerApi ON SOME METHOD!
        // NOT ON CLASS

    }

    @Bean
    public Docket swaggerApi() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.basePackage("controllerPackage"))
                .paths(PathSelectors.any())
                .build()
                .apiInfo(new ApiInfoBuilder().version(apiVersion).title(applicationName).description("Documentation " + applicationName + " API v" + apiVersion)
                        .build());
    }

    @Bean
    public CorsFilter corsFilter() {
        final UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        final CorsConfiguration config = new CorsConfiguration();
        config.setAllowCredentials(true);
        config.addAllowedOrigin("*");
        config.addAllowedHeader("*");
        config.addAllowedMethod("*");
        source.registerCorsConfiguration("/v2/api-docs", config);
        return new CorsFilter(source);
    }
}





@EnableSwaggerApi(controllerPackage="tko.backend.spring.ctrl")
public class Application extends SpringBootServletInitializer {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class, Initializer.class);
    }


    @Bean
    @EnableSwaggerApi(controllerPackage="tko.backend.spring.SOMEOTHERSTUFF")
    public String initSwagger() {
        return "some dummy";
    }

}

How can I can rid of the annotation on initSwagger()? Since the Application.class is not known to SwaggerConfiguration (Swagger Stuff it's in a separate lib) I can't use simple reflection like

Application.class.getAnnotation(EnableSwaggerApi.class)