Retrieve annotation by name

Question

I know it's possible to get a class by name, using

public String className = "someName"; public Class<?> c = Class.forName(className);

Is it possible to retrieve an annotation by name? I tried this:

public String annotationName = "someName"; public Class<?> c = Class.forName(annotationName);

And then casting c to Class<? extends Annotation>, which works, but I get an Unchecked cast warning.

I also tried

public String annotationName = "someName"; public Class<? extends Annotation> c = Class.forName(annotationName);

But when I do that I get the error

Incompatible types. Required: Class<? extends java.lang.annotation.Annotation> Found: Class<Capture<?>>

Possible duplicate of How to get annotation class name, attribute values using reflection — Hadi
– Hadi, Commented May 12, 2019 at 9:01
@HadiJ If I understand correctly, that question deals with trying to retrieve all annotation names. My question is if I already have a specific annotation name, how to get to the annotation — Alon Jacobi
– Alon Jacobi, Commented May 12, 2019 at 9:05
The first way you showed is the way to do it. You can't do anything to the unchecked cast warning except to suppress it. That's just a limitation in Java's generics. — Sweeper
– Sweeper, Commented May 12, 2019 at 9:07
And then casting c to Class<? extends Annotation>, which works - can't be possible, bounded types only work if they involve an interface or class — Eugene
– Eugene, Commented May 12, 2019 at 10:01

Holger · Accepted Answer · 2019-05-13 08:00:16Z

Use asSubclass. Unlike compiler generated type casts, which can only work with types known at compile-time, this will perform a check against the Class object retrieved at runtime. Since this is safe, it won’t generated an “Unchecked cast” warning. Note the existence of a similar operation, cast for casting an instance of a Class. These methods were added in Java 5, specifically to aid code using Generics.

String annotationName = "java.lang.Deprecated"; Class<? extends Annotation> c = Class.forName(annotationName).asSubclass(Annotation.class); boolean depr = Thread.class.getMethod("stop").isAnnotationPresent(c); System.out.println(depr);

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