I have a bunch of proxy objects and I need to identify which classes and interfaces these objects are instance of besides Proxy. In other words, I am not actually looking for the instanceof operator, instead I'm looking to get all classes and interfaces for which instanceof would return true for a particular object.
1
-
4Can you share your research into this heavily documented feature? That way we know what knowledge you already have of the subject.Jeroen Vannevel– Jeroen Vannevel2015-02-10 17:26:50 +00:00Commented Feb 10, 2015 at 17:26
Add a comment
|
3 Answers
You can use reflection to determine this. Fundamentally the Java Class class contains accessors which list the interfaces and superclass.
Class clazz = someObject.getClass();
clazz.getInterfaces();
clazz.getSuperclass();
You should read further about the Java Reflection API. A good place might be to start with the Class documentation.
Comments
You should use the Class.getInterfaces() and Class.getSuperclass() methods. I believe these will need recursion; an example is:
<T> Set<Class<? super T>> getSuperclasses(Class<? super T> clazz) {
Set<Class<? super T>> superclasses = new HashSet<>();
if (clazz.getSuperclass() != null) {
superclasses.addAll(getSuperclasses(clazz.getSuperclass()));
}
return superclasses;
}
And interfaces:
<T> Set<Class<? super T>> getSuperInterfaces(Class<T> clazz) {
Set<Class<? super T>> superInterfaces = new HashSet<>();
if (clazz.getInterfaces().length != 0) {
// Only keep the one you use
// Java 7:
for (Class<?> superInterface : clazz.getInterfaces()) {
// noinspection unchecked
superInterfaces.add((Class<? super T>) superInterface);
}
// Java 8:
// noinspection unchecked
Arrays.stream(clazz.getInterfaces()).map(c -> (Class<? super T>) c).forEach(superInterfaces::add);
}
return superInterfaces;
}
1 Comment
adam smith
getSuperclasses doesn't handle the base case and getSuperInterfaces doesn't recurse.With Reflection API you can achieve what you want. You would have to scan the packages you want to search for classess the implements or extends a particular interface/class.
1 Comment
toolforger
The package scan is for the reverse operation, which was not the OP's question. Package scanning is also a pretty dubious technique because you do not always know all potential sources of packages, the most common being jar files, class files, Internet connections, and bytecode generators.