Java自定义注释

Question

I want to write custome annonation on method .my usecase is - I have user which has role so when user try to access some method of class then i want to check his roles. so roles i want pass in annotation.

my code is here package com.samples;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


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

public String roles();
}


package com.samples;

public class AnnotationExample {

@Roles(roles="admin")
public void createAction(){
String userrole = "admin"; // this hardcoded value
            // a
// here i want to compare annotaiton value with user role


}
}

How can i do this ? It is possible to declare annotation value as object value. like @Roles(Role.AADMIN)

Answer 1

To check the annotations you need to use reflection.

Roles r = AnnotationExample.class.getMethod("createAction").getAnnotation(Roles.class);
if ("admin".equals(r.roles())) //has admin roles

It is possible to declare annotation value as object value. like @Roles(Role.AADMIN)

I think what you want is a Enum.

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

   public Role roles();
}

enum Role { ADMIN, USER };

public class AnnotationExample {

   @Roles(roles=Role.ADMIN)
   public void createAction(){
      Role userrole = Role.ADMIN;
    }
}

Answer 2

If you really need to reinvent security annotations (if you don't want to use already available options with declarative security like EJB or Spring) you may at least want to see how they implement it. Here for example for one of EJB implementations.

But maybe you would reconsider?