How to get method annotation value

I am writing a plugin for parsing a jar archive, using the url classloader, I get reflective access to the classes of this archive, I have annotation names by which I can find the classes corresponding to them in the bytecode (for obvious reasons, I do not have access to the annotation class itself from the code that is currently parsing this jar), I'm sure there is some dirty trick to do this, please help

for example what i am doing in nutshell:

Path pathToJar = Paths.get("/a/b/c/Application.jar");

List<Class<?>> allJarClasses = loadAllJarClasses(pathToJar);

String annotationName = "MyAnnotation";

getValueFromAnnotationWithName(annotationName, allJarClasses);

---

public String getValueFromAnnotationWithName(String annotationName, List<Class<?>> classes) {
    classes.forEach(cl -> {
        Method[] methods = ...getMethods
        for(Method m : methods) {
            Annotations[] annotations = ...getAnnotations from method
            for (Annotation a: annotations) {
               if (a.annotationType().getName().matches(".*" + annotationName)) {
                     return getValueFromAnnotation("someValueName", a); <- here i need help;
               }
            }
        }
    });
}

Update: i can get values while debugging in intellij idea

also if do this:

annotationMethod.toString()

i can get this:

@ru.sparural.kafka.annotation.KafkaSparuralMapping(value="file/create")