Download as PDF, PPTX
![M. Dmitriev. Safe class and data evolution in large and long-lived java[tm] applications. Technical report, Mountain View, CA, 2001.](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-18-2048.jpg)
![public class C extends X {
int y = 5;
int method1(int x) {
Object[] o = new Object[1];
o[0] = x;
return Runtime.redirect(this, o, "C", "method1", "(I)I");
}
void method2(String s) {
Object[] o = new Object[1];
o[0] = s;
return Runtime.redirect(
this, o, "C", "method2", "(Ljava/lang/String;)V");
}
}](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-27-2048.jpg)
![public abstract class C0 {
public static int method1(C c, int x) {
int tmp1 = Runtime.getFieldValue(c, "C", "y", "I");
return x + tmp1;
}
public static void method2(C c, String s) {
PrintStream tmp1 = Runtime.getFieldValue(
null, "java/lang/System", "out", "Ljava/io/PrintStream;");
Object[] o = new Object[1];
o[0] = s;
Runtime.redirect(
tmp1, o, "java/io/PrintStream;", "println",
"(Ljava/lang/String;)V");
}
}](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-28-2048.jpg)
![package a;
public class A {
int say() {return 1;}
}
package a;
class Test {
public static void main(String args[]) {
a.A a = new b.B();
System.out.println(a.say());
}
}
package b;
public class B extends a.A {
int say() {return 2;}
}
An Exercise](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-35-2048.jpg)
![new ClassFileTransformer() {
public byte[] transform(ClassLoader loader,
String className,
Class<?>classBeingRedefined,
ProtectionDomain protectionDomain,
byte[] classfileBuffer){
ClassPool cp = ClassPool.getDefault();
CtClass ct = cp.makeClass(new
ByteArrayInputStream(classfileBuffer));
transformClass(ct, cp);
return ct.toBytecode();
}
}](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-44-2048.jpg)
![new ClassFileTransformer() {
public byte[] transform(ClassLoader loader,
String className,
Class<?>classBeingRedefined,
ProtectionDomain protectionDomain,
byte[] classfileBuffer){
ClassPool cp = ClassPool.getDefault();
CtClass ct = cp.makeClass(new
ByteArrayInputStream(classfileBuffer));
transformClass(ct, cp);
return ct.toBytecode();
}
}](https://image.slidesharecdn.com/jrebelunderthecoversdevoxxpl-150624071331-lva1-app6891/75/DevoxxPL-JRebel-Under-The-Covers-45-2048.jpg)
Uploaded bySimon Maple
DevoxxPL: JRebel Under The Covers
The document outlines JRebel's capabilities for real-time Java application code reloading without losing application state, emphasizing its use of class loaders and hotswap features. It discusses various methods for changing and updating Java code during development, including adding/removing methods and fields, while preventing issues like memory leaks. Additionally, it highlights performance improvements and benefits experienced by teams using JRebel, such as significant increases in development velocity.
More Related Content
Similar to DevoxxPL: JRebel Under The Covers
DevoxxPL: JRebel Under The Covers
- 1. JRebel Under the Covers How is it even possible?
- 2. Simon Maple -‐ @sjmaple @sjmapleSimon Maple
- 5. Make a change Compile Build Deploy Observethe result Take some coffee Avg: 3 min
- 7.
- 8. How can Ireload a single class preserving the state?
- 9.
- 11. How to reloadweb application? (and preserve state)
- 12.
- 13.
- 14. Class loaders aregood for isolation, but suck at reloading the code … (and perfect for memory leaks)
- 16.
- 17. Hello, HotSwap! Hotswapping methodssince 2002
- 18. M. Dmitriev. Safeclass and data evolution in large and long-lived java[tm] applications. Technical report, Mountain View, CA, 2001.
- 19. The Heap & Garbage CollecBon
- 20. Hello, JRebel! Improving HotSwapsince 2007
- 21.
- 22. HotSwap JRebel Changing method bodies Adding/removing methods Adding/removing constructors Adding/removing fields Adding/removing annotaBons Changing superclass Adding/removing interfaces
- 23. How does itwork???
- 24.
- 25.
- 26. public class Cextends X { int y = 5; int method1(int x) { return x + y; } void method2(String s) { System.out.println(s); } }
- 27. public class Cextends X { int y = 5; int method1(int x) { Object[] o = new Object[1]; o[0] = x; return Runtime.redirect(this, o, "C", "method1", "(I)I"); } void method2(String s) { Object[] o = new Object[1]; o[0] = s; return Runtime.redirect( this, o, "C", "method2", "(Ljava/lang/String;)V"); } }
- 28. public abstract classC0 { public static int method1(C c, int x) { int tmp1 = Runtime.getFieldValue(c, "C", "y", "I"); return x + tmp1; } public static void method2(C c, String s) { PrintStream tmp1 = Runtime.getFieldValue( null, "java/lang/System", "out", "Ljava/io/PrintStream;"); Object[] o = new Object[1]; o[0] = s; Runtime.redirect( tmp1, o, "java/io/PrintStream;", "println", "(Ljava/lang/String;)V"); } }
- 29. public class Cextends X { int y = 5; int method1(int x) { return x + y; } //... } public class C extends X { int y = 5; int z() { return 10; } int method1(int x) { return x + y + z(); } //... }
- 30. public class C1{ public static int z(C c) { return 10; } public static int method1(C c, int x) { int tmp1 = Runtime.getFieldValue(c, "C", "y", "I"); int tmp2 = Runtime.redirect(c, null, "C", "z", "(V)I"); return x + tmp1 + tmp2; } //... }
- 31.
- 34. static { } Addingnew static fields Removing static fields Changing values of static fields Factories etc
- 35. package a; public classA { int say() {return 1;} } package a; class Test { public static void main(String args[]) { a.A a = new b.B(); System.out.println(a.say()); } } package b; public class B extends a.A { int say() {return 2;} } An Exercise
- 36. “package” visibility package ->public -> package
- 37.
- 38.
- 39.
- 41.
- 42. Javassist: binary patching forfun and profit
- 43. import java.lang.instrument.ClassFileTransformer; import java.lang.instrument.Instrumentation; publicclass Agent { public static void premain(String args, Instrumentation inst) throws Exception { inst.addTransformer(new ClassFileTransformer { }); } } java –javaagent:agent.jar … META-INF/MANIFEST.MF Premain-Class: Agent
- 44. new ClassFileTransformer() { publicbyte[] transform(ClassLoader loader, String className, Class<?>classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); transformClass(ct, cp); return ct.toBytecode(); } }
- 45. new ClassFileTransformer() { publicbyte[] transform(ClassLoader loader, String className, Class<?>classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer){ ClassPool cp = ClassPool.getDefault(); CtClass ct = cp.makeClass(new ByteArrayInputStream(classfileBuffer)); transformClass(ct, cp); return ct.toBytecode(); } }
- 46.
- 47. @Path(“/”) public String foo(){ return “Foo”; } @Path(“/foobar”) public String foo() { return “FooBar”; } JRebel core JRebel Spring plugin
- 48.
- 49.
- 50. http://zeroturnaround.com/company/case-studies/ “Team velocity wasincreased by 40.6%, and according to t-test it was a statistically significant difference.” “Netty and Spring together with JRebel is real pleasure to work with. The value of time saved is over 50% of my development time.”
- 51.
- 54.