JavaZone 2017 - The hitchhicker's guide to Java class reloading

Transcript

1. The hitchhiker’s guide to Java class reloading @antonarhipov
2. whoami Anton Arhipov @antonarhipov
3. whoami Anton Arhipov @antonarhipov
6. https://zeroturnaround.com/rebellabs/java-ee-productivity-report-2011/ 10% 20% 30% 0.5 1 2 3 4 5 6 7 8 10+ minutes
7. https://zeroturnaround.com/rebellabs/java-ee-productivity-report-2011/ 10% 20% 30% 0.5 1 2 3 4 5 6 7 8 10+ The only effective developers?? minutes
8. https://zeroturnaround.com/rebellabs/java-ee-productivity-report-2011/ 10% 20% 30% 0.5 1 2 3 4 5 6 7 8 10+ How about those? minutes
10. HotSwap
11. HotSwap Class loaders
12. HotSwap Class loaders Java agents & instrumentation
13. HotSwap Class loaders Java agents & instrumentation
14. hotswap EST. 2001
24. HOW ABOUT… refactoring?
28. JDB
29. 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
30. 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
31. 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
32. 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
33. What if… hotswap++
34. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010
35. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements
36. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods
37. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields
38. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy
39. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy
40. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy + + + Binary-compatible
41. Dynamic Code Evolution for Java T. Würthinger, C. Wimmer, L. Stadler. 2010 Statements Methods Fields Hierarchy + + + x x x Binary-compatible Binary-incompatible
43. Classloaders
44. 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$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
45. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$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; }
46. 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$AppClassLoader@18b4aac2 out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7 User.age = 11; out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11 out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10 public class User { public static int age = 10; }
47. Class<?> uc1 = User.class; Class<?> uc2 = new DynamicClassLoader().load("com.zt.User"); out.println(uc1.getName()); // com.zt.User out.println(uc2.getName()); // com.zt.User out.println(uc1.getClassLoader()); // sun.misc.Launcher$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; }
48. 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; }
49. while(true) { Class<?> uc = new DynamicClassLoader().load("com.zt.User"); ReflectUtil.invokeStatic("getHobby", uc); } public class User { public Hobby getHobby() { return Basketball(); } }
50. while(true) { Class<?> uc = new DynamicClassLoader().load("com.zt.User"); ReflectUtil.invokeStatic("getHobby", uc); } public class User { public Hobby getHobby() { return Basketball(); } }
51. public static class Context { public HobbyService hobbyService = new HobbyService(); public void init() { hobbyService.user = new User(); anyService.initialize() } }
52. public static class Context { public HobbyService hobbyService = new HobbyService(); public AnyService anyService = new AnyService(); public void init() { hobbyService.user = new User(); anyService.initialize() } }
53. 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); }
54. DynamicClassLoader Context class HobbyService class User class Context object HobbyService object User object Reloadable “region” Live thread
57. <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> </dependency> DEMO
61. Java agents
62. import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentation inst) throws Exception { inst.addTransformer(new ClassFileTransformer { // here be dragons }); } }
63. import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentation inst) throws Exception { inst.addTransformer(new ClassFileTransformer { // here be dragons }); } } META-INF/MANIFEST.MF Premain-Class: Agent
64. import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; public class Agent { public static void premain(String args, Instrumentation inst) throws Exception { inst.addTransformer(new ClassFileTransformer { // here be dragons }); } } $> java –javaagent:agent.jar application.Main META-INF/MANIFEST.MF Premain-Class: Agent
65. 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
66. 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
69. HotSwap
70. HotSwap Class loaders
71. HotSwap Class loaders Java agents & instrumentation
72. anton@zeroturnaround.com @antonarhipov