41. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods
42. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods Fields
43. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods Fields Hierarchy
44. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods Fields Hierarchy
45. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods Fields Hierarchy
+ + +
Binary-compatible
46. Dynamic Code Evolution for Java
T. Würthinger, C. Wimmer, L. Stadler. 2010
Statements
Methods Fields Hierarchy
+ + +
x x x
Binary-compatible
Binary-incompatible
49. 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$AppClassLoader@18b4aac2
out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7
User.age = 11;
out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11
out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10
public class User {
public static int age = 10;
}
50. Class<?> uc1 = User.class;
Class<?> uc2 = new DynamicClassLoader().load("com.zt.User");
out.println(uc1.getName()); // com.zt.User
out.println(uc2.getName()); // com.zt.User
out.println(uc1.getClassLoader()); // sun.misc.Launcher$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;
}
51. 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$AppClassLoader@18b4aac2
out.println(uc2.getClassLoader()); // com.zt.DynamicClassLoader@22b4bba7
User.age = 11;
out.println((int) ReflectUtil.getStaticFieldValue("age", uc1)); // 11
out.println((int) ReflectUtil.getStaticFieldValue("age", uc2)); // 10
public class User {
public static int age = 10;
}
52. Class<?> uc1 = User.class;
Class<?> uc2 = new DynamicClassLoader().load("com.zt.User");
out.println(uc1.getName()); // com.zt.User
out.println(uc2.getName()); // com.zt.User
out.println(uc1.getClassLoader()); // sun.misc.Launcher$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;
}
53. 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;
}
54. while(true) {
Class<?> uc = new DynamicClassLoader().load("com.zt.User");
ReflectUtil.invokeStatic("getHobby", uc);
}
public class User {
public Hobby getHobby() {
return Basketball();
}
}
55. while(true) {
Class<?> uc = new DynamicClassLoader().load("com.zt.User");
ReflectUtil.invokeStatic("getHobby", uc);
}
public class User {
public Hobby getHobby() {
return Basketball();
}
}
56. while(true) {
Class<?> uc = new DynamicClassLoader().load("com.zt.User");
ReflectUtil.invokeStatic("getHobby", uc);
}
public class User {
public Hobby getHobby() {
return Basketball();
}
}
Assume there is a trigger / event
57. public static class Context {
public HobbyService hobbyService = new HobbyService();
public void init() {
hobbyService.user = new User();
anyService.initialize()
}
}
58. public static class Context {
public HobbyService hobbyService = new HobbyService();
public AnyService anyService = new AnyService();
public void init() {
hobbyService.user = new User();
anyService.initialize()
}
}
59. 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);
}
75. What did we learn today?
HotSwap - a feature of your JVM, not IDE!
76. What did we learn today?
HotSwap - a feature of your JVM, not IDE!
Class loaders - easy to implement, but limited
77. What did we learn today?
HotSwap - a feature of your JVM, not IDE!
Class loaders - easy to implement, but limited
Java agents & instrumentation - very tricky!