@CallerSensitive as public API ? (original) (raw)

Dr Heinz M. Kabutz heinz at javaspecialists.eu
Wed Jun 26 09:40:24 UTC 2013

Remi Forax wrote:

On 06/26/2013 03:10 AM, Dr Heinz M. Kabutz wrote:

Hi Peter,

here is another use case, where someone might want to use this: 3 - in a static context, find out what the class is that you are in. For example, if you want to create a logger, instead of doing this: private static final Logger log = Logger.getLogger(SomeClass.class); we could instead have a magic method that figures out what class this is being called from and then sets the class automatically. There are two other ways to do this, but they are a lot slower than Reflection.getCallerClass(): 1. http://www.javaspecialists.eu/archive/Issue137.html - create an exception and figure out who the calling class is 2. Or we can use the SecurityManager to get us a stack of contexts. For example, in the exercises for my courses, some students had problems with the JUnit plugin. So each test case also contains the main method, but it is always the same: public static void main(String[] args) { UnitTestRunner.run(); } My UnitTestRunner then depends on the security manager to decide what the actual class is and then uses the JUnit4TestAdapter to call the methods: import junit.framework.*; import junit.textui.*; public class UnitTestRunner { private static void run(Class clazz) { System.out.println("Running unit tests for " + clazz); TestRunner.run(new JUnit4TestAdapter(clazz)); } public static void run() { MySecurityManager sm = new MySecurityManager(); Class clazz = sm.getClassContext()[2]; run(clazz); } private static class MySecurityManager extends SecurityManager { public Class[] getClassContext() { return super.getClassContext(); } } } Works like a charm. Fortunately this is not affected by the Reflection.getCallerClass() bug. Just my 2c :-) Regards Heinz Hi Heinz, You can also use the JSR 292 Lookup object MethodHandles.lookup().lookupClass() Brilliant, thanks Rémi! I've learned something new :-)

However, in this case it would not work as I need to find the calling class, not the UnitTestRunner class. Is there a way to find out which class called you with MethodHandles?

Heinz

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