2. Binary patching of Java classes for funand profit Jfokus 2011, Stockholm

3. whoami Anton Arhipov ZeroTurnaround JRebel http://arhipov.blogspot.com @antonarhipov @javarebel

4. What’s Binary Patching? Ninja.class’ Ninja.class 1010101010111000101010101010100010001000111011011101011 1010101010111100001010101010100010001000111011011101110

5. Why Binary Patching? ClassLoader MyClass.class JRebel agent New code: 10010100100100101011001010 MyObject

6. Why Binary Patching? ClassLoader MyClass.class Framework JRebel agent New code: 10010100100100101011001010 MyObject

7. Why Binary Patching? ClassLoader MyClass.class Framework JRebel agent New code: 10010100100100101011001010 MyObject Configuration (XML, annotations)

8. How? Using –javaagentto hook into class loading process Using bytecode manipulation libraries (e.g. Javassist)

9. java.lang.instrument importjava.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentationinst) throws Exception { inst.addTransformer(new ClassFileTransformer { … }); } }

10. java.lang.instrument importjava.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentationinst) throws Exception { inst.addTransformer(new ClassFileTransformer { … }); } } META-INF/MANIFEST.MF Agent-Class: Agent

11. java.lang.instrument importjava.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentationinst) throws Exception { inst.addTransformer(new ClassFileTransformer { … }); } } META-INF/MANIFEST.MF Agent-Class: Agent java –javaagent:agent.jar …

12. java.lang.instrument + Javassist newClassFileTransformer() { public byte[] transform(ClassLoaderloader, String className, Class<?>classBeingRedefined, ProtectionDomainprotectionDomain, byte[] classfileBuffer){ } }

13. java.lang.instrument + Javassist newClassFileTransformer() { public byte[] transform(ClassLoaderloader, String className, Class<?>classBeingRedefined, ProtectionDomainprotectionDomain, byte[] classfileBuffer){ ClassPoolcp= ClassPool.getDefault(); CtClassct= pool.makeClass(new ByteArrayInputStream(classfileBuffer)); } }

14. java.lang.instrument + Javassist newClassFileTransformer() { public byte[] transform(ClassLoaderloader, String className, Class<?>classBeingRedefined, ProtectionDomainprotectionDomain, byte[] classfileBuffer){ ClassPoolcp= ClassPool.getDefault(); CtClassct= pool.makeClass(new ByteArrayInputStream(classfileBuffer)); transformClass(ct, cp); } }

15. java.lang.instrument + Javassist newClassFileTransformer() { public byte[] transform(ClassLoaderloader, String className, Class<?>classBeingRedefined, ProtectionDomainprotectionDomain, byte[] classfileBuffer){ ClassPoolcp= ClassPool.getDefault(); CtClassct = pool.makeClass(new ByteArrayInputStream(classfileBuffer)); transformClass(ct, cp); returnct.toBytecode(); } }

16. JRebel SDK

17. Javassist + JRebel cp.importPackage("org.zeroturnaround.javarebel");

18. Javassist + JRebel cp.importPackage("org.zeroturnaround.javarebel"); ct.addInterface( cp.get(ClassEventListener.class.getName()));

19. Javassist + JRebel cp.importPackage("org.zeroturnaround.javarebel"); ct.addInterface( cp.get(ClassEventListener.class.getName())); ct.addMethod(CtNewMethod.make( "public void onClassEvent(inteventType, Class clazz) {"+ "cache.evict();" + "}", ct));

20. Javassist + JRebel CtClassct = … CtConstructor[] cs = ct.getConstructors();

21. Javassist + JRebel CtClassct = … CtConstructor[] cs = ct.getConstructors(); for (CtConstructor c : cs) { if(c.callsSuper()) { c.insertAfter("ReloaderFactory.getInstance() .addClassReloadListener($0);"); } }

22. Javassist + JRebel CtClassct = … ct.getDeclaredMethod("service") .insertBefore( "ReloaderFactory.getInstance() .checkAndReload(Application.class);");

23. Integration Highlights Implement ClassEventListener Register listener instance to JRebel Trigger the re-load event ReloaderFactory#addClassReloadListener(…); ReloaderFactory#checkAndReload(…);

24. Pros/Cons

25. Pros/Cons

26. Pros/Cons

27. Thx! Want JRebel free? Come to our booth!