Classloading, Reflection, and Method Handles - Java in a Nutshell - page 324

e . printStackTrace ();
} catch ( IllegalAccessException | InvocationTargetException x ) {
x . printStackTrace ();
}
However, it should be pointed out that reflection always involves unknown infor‐
mation. To some degree, we just have to live with some of this verbosity as the price
of dealing with reflective invocation, and the dynamic, runtime power that it gives
to the developer.
As a final example in this section, let's show how to combine reflection with custom
classloading to inspect a class file on disk and see if it contains any deprecated
methods (these should be marked with @Deprecated ):
public class CustomClassloadingExamples {
public static class DiskLoader extends ClassLoader {
public DiskLoader () {
super ( DiskLoader . class . getClassLoader ());
}
public Class <?> loadFromDisk ( String clzName )
throws IOException {
byte [] b = Files . readAllBytes ( Paths . get ( clzName ));
return defineClass ( null , b , 0 , b . length );
}
}
public void findDeprecatedMethods ( Class <?> clz ) {
for ( Method m : clz . getMethods ()) {
for ( Annotation a : m . getAnnotations ()) {
if ( a . annotationType () == Deprecated . class ) {
System . out . println ( m . getName ());
}
}
}
}
public static void main ( String [] args )
throws IOException , ClassNotFoundException {
CustomClassloadingExamples rfx =
new CustomClassloadingExamples ();
if ( args . length > 0 ) {
DiskLoader dlr = new DiskLoader ();
Class <?> clzToTest = dlr . loadFromDisk ( args [ 0 ]);
rfx . findDeprecatedMethods ( clzToTest );
}
}
}