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Method Security in GraalVM Native Image

Although Method Security is supported in GraalVM Native Image, there are some use cases that need additional hints provided by the application.

Using @PreAuthorize and @PostAuthorize Annotations

Using @PreAuthorize and @PostAuthorize annotations require additional hints if you have a custom implementation of UserDetails or Authentication classes.

Let’s take an example where you have a custom implementation of UserDetails class as follows and that implementation is returned by your UserDetailsService:

Custom Implementation of UserDetails
public class CustomUserDetails implements UserDetails {

    private final String username;

    private final String password;

    private final Collection<? extends GrantedAuthority> authorities;

    public boolean isAdmin() {
        return this.authorities.contains(new SimpleGrantedAuthority("ROLE_ADMIN"));
    }

    // constructors, getters and setters
}

And you want to use the isAdmin() method inside a @PreAuthorize annotation as follows:

Using isAdmin() to secure a method
@PreAuthorize("principal?.isAdmin()")
public String hello() {
    return "Hello!";
}

Remember that you need to add @EnableMethodSecurity annotation to your configuration class to enable method security annotations.

If you run the native image of your application with the above configuration, you will get an error similar to the following when trying to invoke the hello() method:

failed: java.lang.IllegalArgumentException: Failed to evaluate expression 'principal?.isAdmin()' with root cause
org.springframework.expression.spel.SpelEvaluationException: EL1004E: Method call: Method isAdmin() cannot be found on type com.mypackage.CustomUserDetails

Which means that the isAdmin() method cannot be found on the CustomUserDetails class. This is because Spring Security uses reflection to invoke the isAdmin() method and GraalVM Native Image does not support reflection by default.

To fix this issue, you need to give hints to GraalVM Native Image to allow reflection on the CustomUserDetails#isAdmin() method. We can do that by providing a custom hint. In this example we are going to use the @RegisterReflectionForBinding annotation.

You might need to register all your classes that you want to use in your @PreAuthorize and @PostAuthorize annotations.
Using @RegisterReflectionForBinding
@Configuration
@RegisterReflectionForBinding(CustomUserDetails.class)
public class MyConfiguration {
    //...
}

And that’s it, now you can run the native image of your application and it should work as expected.