Can Java Annotations Accept Dynamically Generated Values at Runtime?

Evaluating Annotations at Runtime

In Java, annotations are useful for providing metadata to a compiler or runtime system. However, an ongoing question is if annotations can accept values dynamically generated at runtime.

The attempt below attempts to generate a string value for the aString attribute of @MyInterface:

<code class="java">@MyInterface(aString = MyClass.GENERIC_GENERATED_NAME)
public class MyClass {

    static final String GENERIC_GENERATED_NAME = MyClass.generateName(MyClass.class);

    public static final String generateName(final Class<?> c) {
        return c.getClass().getName();
    }
}</code>

However, the compiler will reject this with the error message:

The value for annotation attribute MyInterface.aString must be a constant expression

This is because annotations are evaluated at compile time, but GENERIC_GENERATED_NAME is not known until runtime.

To achieve the desired effect, it would be necessary to create an annotation processor that could evaluate the generateName method at compile time. However, this solution has limitations, as there is no support in Java for evaluating code dynamically at runtime.

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