Modify a class definition's annotation string parameter at runtime

Question

Imagine there is a class:

@Something(someProperty = \"some value\")
public class Foobar {
    //...
}

Which is already compiled (I cannot c

Answer 1

This one works on my machine with Java 8. It changes the value of ignoreUnknown in the annotation @JsonIgnoreProperties(ignoreUnknown = true) from true to false.

final List matchedAnnotation = Arrays.stream(SomeClass.class.getAnnotations()).filter(annotation -> annotation.annotationType().equals(JsonIgnoreProperties.class)).collect(Collectors.toList());    

final Annotation modifiedAnnotation = new JsonIgnoreProperties() {
    @Override public Class annotationType() {
        return matchedAnnotation.get(0).annotationType();
    }    @Override public String[] value() {
        return new String[0];
    }    @Override public boolean ignoreUnknown() {
        return false;
    }    @Override public boolean allowGetters() {
        return false;
    }    @Override public boolean allowSetters() {
        return false;
    }
};    

final Method method = Class.class.getDeclaredMethod("getDeclaredAnnotationMap", null);
method.setAccessible(true);
final Map, Annotation> annotations = (Map, Annotation>) method.invoke(SomeClass.class, null);
annotations.put(JsonIgnoreProperties.class, modifiedAnnotation);