JEEConf 2017 - The hitchhiker's guide to Java class reloading

Transcript

1. The hitchhiker’s guide to Java class reloading JEEConf 2017 @antonarhipov
2. whoami Anton Arhipov @antonarhipov
3. whoami Anton Arhipov @antonarhipov
6. HotSwap
7. HotSwap Class loaders
8. HotSwap Class loaders Java agents & instrumentation
9. hotswap EST. 2001
19. HOW ABOUT… refactoring?
23. JDB
24. instanceKlass constantPoolOop constants() pool_holder() klassVTable Embedded klassITable Embedded Embedded statics M. Dmitriev. Safe class and data evolution in large and long-lived Java (тм) applications. Technical report, Mountain View. 2001
25. instanceKlass constantPoolOop constants() constantPoolCacheOop cache() pool_holder() klassVTable Embedded klassITable Embedded Embedded statics M. Dmitriev. Safe class and data evolution in large and long-lived Java (тм) applications. Technical report, Mountain View. 2001
26. instanceKlass constantPoolOop constants() constantPoolCacheOop cache() pool_holder() klassVTable Embedded klassITable Embedded Embedded statics objArrayOop methodOop methods() M. Dmitriev. Safe class and data evolution in large and long-lived Java (тм) applications. Technical report, Mountain View. 2001
27. instanceKlass constantPoolOop constants() constantPoolCacheOop cache() pool_holder() klassVTable Embedded klassITable Embedded Embedded statics nmethod code() method() constants() objArrayOop methodOop methods() M. Dmitriev. Safe class and data evolution in large and long-lived Java (тм) applications. Technical report, Mountain View. 2001
28. What if… hotswap++
29. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010
30. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements
31. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods
32. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields
33. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy
34. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy
35. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy + + + Binary-compatible
36. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy + + + x x x Binary-compatible Binary-incompatible
38. Classloaders
39. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
40. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
41. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
42. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
43. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
44. while(true) { Class<?> uc = new DynamicClassLoader().load("com.zt.User"); ReflectUtil.invokeStatic("getHobby", uc); } public class User { public Hobby getHobby() { return Basketball(); } }
45. while(true) { Class<?> uc = new DynamicClassLoader().load("com.zt.User"); ReflectUtil.invokeStatic("getHobby", uc); } public class User { public Hobby getHobby() { return Basketball(); } }
46. public static class Context { public HobbyService hobbyService = new HobbyService(); public void init() { hobbyService.user = new User(); anyService.initialize() } }
47. public static class Context { public HobbyService hobbyService = new HobbyService(); public AnyService anyService = new AnyService(); public void init() { hobbyService.user = new User(); anyService.initialize() } }
48. public static class Context { public HobbyService hobbyService = new HobbyService(); public AnyService anyService = new AnyService(); public void init() { hobbyService.user = new User(); anyService.initialize() } } while(true) { Class<?> c = new DynamicClassLoader().load("com.zt.Context"); Object context = c.newInstance(); ReflectUtil.invokeMethod("init", context); invokeService(context); }
49. DynamicClassLoader Context class HobbyService class User class Context object HobbyService object User object Live thread
52. <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> </dependency> DEMO
56. Java agents
58. ClassFileTransformer ClassA ClassA ClassA0 +field1 +field2 +field3 +method1 +method2 +method3 +method1 +method2 +method3 +field1 +field2 +field3 +proxy_methods A thousand years of productivity: the JRebel story E. Kabanov, V. Vene, 2012
59. ClassFileTransformer ClassA ClassA ClassA0 +field1 +field2 +field3 +method1 +method2 +method3 +method1 +method2 +method3 +field1 +field2 +field3 +proxy_methods A thousand years of productivity: the JRebel story E. Kabanov, V. Vene, 2012
60. DEMO
62. HotSwap
63. HotSwap Class loaders
64. HotSwap Class loaders Java agents & instrumentation
65. anton@zeroturnaround.com @antonarhipov