1. NetBeans Plugin Development:
JRebel Experience Report
JavaOne SF 2012

3. whoami
Anton Arhipov
JRebel Product Lead
@antonarhipov
anton@zeroturnaround.com

4. Agenda
• JRebel intro
– Plugin requirements
• NetBeans plugin development
• Integrating with NetBeans server adaptors
• Integrating with NetBeans debugger
• Packaging & publishing

5. ENTER JREBEL

6. The Turnaround Cycle
Make
changes
AVG 2.5 min
Build,
Observe
deploy,
results
wait

7. Make changes
in IDE
ClassLoader
Framework
MyObject.class
Code
101000101
New code
JRebel
100010010
111000100
101010010
MyObject
Configuration
(XML, annotations,..)

8. in action

9. Why IDE plugin?
Usability
Automation
Debugger

10. JRebel Plugin for NetBeans
Workbench Settings, UX
JRebel Plugin
NetBeans
Process
VM args
Launcher
Breakpoints
Debugger
Stepping

11. ENTER NETBEANS
PLUGINS

12. Books

13. UI Elements
• Buttons/Actions
• Toolbars/Menus
• Settings/Options
• Popups
• etc

14. layers.xml
<folder name="Actions">
<folder name="JRebel">
<file name="JRebelToggleAction.instance">
<attr name="delegate"
newvalue="o.z.j.n.JRebelToggleAction"/>
</file>
</folder>
</folder>
<folder name="Toolbars">
<folder name="Build">
<file name="JRebelToggleAction.shadow">
<attr name="originalFile"
stringvalue="Actions/JRebel/JRebelToggleAction.instance"/>
<attr name="position" intvalue="250"/>

15. Options

16. Options (Old API)
<folder name="OptionsDialog">
<file name="JRebelOptions.instance">
<attr name="instanceCreate"
methodvalue="o.n.s.o.OptionsCategory.createCategory"/>
<attr name="controller"
newvalue="o.z.j.n.JRebelOptionsPanelController"/>
</file>
</folder>
<folder name="Services">
<file name="org-zeroturnaround-jrebel-netbeans-options.settings"
url="options.xml"/>
</folder>

17. Options (New API)
@OptionsPanelController.SubRegistration(
location = "Advanced",
displayName = "#AdvancedOption_DisplayName_Super",
keywords = "#AdvancedOption_Keywords_Super",
keywordsCategory = "Advanced/Super")
@org.openide.util.NbBundle.Messages(
{"AdvancedOption_DisplayName_Super=Super",
"AdvancedOption_Keywords_Super=super"})
public final class SuperOptionsPanelController
extends OptionsPanelController {

18. CUSTOM JVM
ARGUMENTS

19. JVM arguments
• JRebel is bootstrapped using JVM arguments:
-javaagent:/path/to/jrebel.jar
-noverify -Xbootclasspath/p:jrebel-bootstrap.jar;jrebel.jar
-Drebel.log=true -Drebel.jersey_plugin=true
• Various NetBeans project types pass JVM
arguments slightly differently:
Web project VS Maven project
JBoss VS Tomcat VS Glassfish

20. Server settings: Tomcat
Can put your
arguments here

21. Server settings: Glassfish
No VM
arguments?

22. Project Deployment
Aha!!

23. Toggle
Simplest, from the user’s point of view: should not
care about project type of runtime differences

24. Toggle
public final class JRebelToggleAction extends BooleanStateAction {
public void initialize() {
super.initialize();
setBooleanState(JRebelSettings.isEnabled());
}
public void actionPerformed(ActionEvent ev) {
super.actionPerformed(ev);
JRebelSettings.setEnabled(getBooleanState());
// NbPreferences.forModule(JRebelSettings.class)
// .putBoolean(“enabled”, true);
}
}

25. Challenge
No extension points provided
by the NetBeans platform
Load-Time Weaving of
NetBeans platform classes
Might not be the brightest bulb idea, but seems to work fine 

26. PATCHING THE
PLATFORM

27. org.openide.modules.ModuleInstall
public class Installer extends ModuleInstall {
@Override
public void restored() {
// patch platform classes here
}
}

28. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
.lookup(ClassLoader.class);
Object o = ClassLoader#findLoadedClass(classToPatch )
ClassPool cp = new ClassPool();
cp.appendClassPath(new LoaderClassPath(cl));
CtClass ctc = cp.get(classToPatch);
patch(cp, ctc);
ctc.toClass(cl, null);

29. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
.lookup(ClassLoader.class);
e.g.
Object o = ClassLoader#findLoadedClass(classToPatch )
“org.netbeans.modules.glassfish.common.StartTask”
“org.netbeans.modules.tomcat5.ide.StartTomcat$StartRunnable”
ClassPool cp = new ClassPool();
etc
cp.appendClassPath(new LoaderClassPath(cl));
CtClass ctc = cp.get(classToPatch);
patch(cp, ctc);
ctc.toClass(cl, null);

30. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
.lookup(ClassLoader.class);
Object o = ClassLoader#findLoadedClass(classToPatch )
a class loader capable for finding
ClassPool cp = new ClassPool(); module
resources from any
cp.appendClassPath(new LoaderClassPath(cl));
CtClass ctc = cp.get(classToPatch);
patch(cp, ctc);
ctc.toClass(cl, null);

31. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
.lookup(ClassLoader.class);
Object o = ClassLoader#findLoadedClass(classToPatch )
ClassPool= ClassLoader.class
Method m cp = new ClassPool();
cp.appendClassPath(new LoaderClassPath(cl));
.getDeclaredMethod("findLoadedClass", String.class);
CtClass ctc = cp.get(classToPatch);
m.setAccessible(true);
patch(cp, ctc);
Object o = m.invoke(cl, patchedClassName);
ctc.toClass(cl, null);

32. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
Enter Javassist
.lookup(ClassLoader.class);
Object o = ClassLoader#findLoadedClass(classToPatch )
ClassPool cp = new ClassPool();
cp.appendClassPath(new LoaderClassPath(cl));
CtClass ctc = cp.get(classToPatch);
patch(cp, ctc);
ctc.toClass(cl, null);

33. Patcher
String classToPatch = …
ClassLoader cl = Lookup.getDefault()
.lookup(ClassLoader.class);
Object o = ClassLoader#findLoadedClass(classToPatch )
ClassPool cp = new ClassPool();
cp.appendClassPath(new LoaderClassPath(cl));
CtClass ctc = cp.get(classToPatch);
This is where patching
patch(cp, ctc);
happens really
ctc.toClass(cl, null);

34. patch(…)
final CtMethod method = ctc.getDeclaredMethod("run");
method.instrument(new ExprEditor() {
public void edit(MethodCall m) {
if ("getJavaOpts".equals(m.getMethodName())) {
m.replace(
"if (command == CommandType.START)" +
OPTS + "$_ = opts + $proceed($$);");
}
}
});

35. patch(…)
final CtMethod method = ctc.getDeclaredMethod("run");
method.instrument(new ExprEditor() {
public void edit(MethodCall m) {
Patching
if ("getJavaOpts".equals(m.getMethodName())) {
StartTomcat$StartRunnable#run()
m.replace(
for Tomcat launcher
"if (command == CommandType.START)" +
OPTS + "$_ = opts + $proceed($$);");
}
}
});

36. patch(…)
final CtMethod method = ctc.getDeclaredMethod("run");
method.instrument(new ExprEditor() {
public void edit(MethodCall m) {
if ("getJavaOpts".equals(m.getMethodName())) {
m.replace(
"if (command == CommandType.START)" +
OPTS + "$_ =Should+append custom options
opts $proceed($$);");
} to getJavaOpts result
}
});

37. patch(…)
final CtMethod method = ctc.getDeclaredMethod("run");
String OPTS =
"ClassLoader cl = (ClassLoader) Lookup.getDefault().lookup(ClassLoader.class);" +
method.instrument(new ExprEditor() {
"Class locator = cl.loadClass("org.zeroturnaround.jrebel.netbeans.JRebelLocator");" +
public void edit(MethodCall m) {
"Method getJRebelOptsStr = locator.getMethod("getJRebelOptsStr", null);" +
if ("getJavaOpts".equals(m.getMethodName())) {
"String opts = (String) getJRebelOptsStr.invoke(null, null);";
m.replace(
"if (command == CommandType.START)" +
OPTS + "$_ = opts + $proceed($$);");
}
}
});

38. patch(…)
final CtMethod method = ctc.getDeclaredMethod("run");
String OPTS =
"ClassLoader cl = (ClassLoader) Lookup.getDefault().lookup(ClassLoader.class);" +
method.instrument(new ExprEditor() {
"Class locator = cl.loadClass("org.zeroturnaround.jrebel.netbeans.JRebelLocator");" +
public void edit(MethodCall m) {
"Method getJRebelOptsStr = locator.getMethod("getJRebelOptsStr", null);" +
if ("getJavaOpts".equals(m.getMethodName())) {
"String opts = (String) getJRebelOptsStr.invoke(null, null);";
m.replace(
"if (command == CommandType.START)" +
OPTS + "$_ = opts + $proceed($$);");
}
-javaagent:/path/to/jrebel.jar etc
}
});

39. Pros & Cons
+ Can get stuff done even if the platform doesn’t
provide a proper interface
- Brittle for maintenance

40. New API (7.2)
• SPI for JVM options passed to SE program or
EE server (Bug 206196)
@StartupArgumentsProvider.Registration(
position=10, displayName="#DESC_JRebel",
startMode={StartMode.NORMAL, StartMode.DEBUG})
public class MyArgsProvider
implements StartupArgumentsProvider {
@Override
public List<String> getArguments(ServerInstance instance,
StartMode mode)

41. Dude, where’s my car breakpoint?
DEBUGGER
INTEGRATION

42. Breakpoints
Line 11: initial breakpoint

43. Breakpoints
Line 14: same breakpoint,
but new version of the class
Need to “transfer” the breakpoint
from original class to versioned class

44. Patching
• o.n.m.d.jpda.breakpoints.LineBreakpointImpl
– setRequests
– getLocations

45. New API (7.3)
• Allow to provide additional binary classes to
submit breakpoints on (Bug 215680)
@BreakpointClassFilter.Registration
public class MyFilter extends BreakpointClassFilter {
@Override
public ClassNames filterClassNames(ClassNames classNames,
JPDABreakpoint breakpoint){}
}

46. RELEASING THE PLUGIN

47. Packaging

48. Packaging
Plugin has to be signed
Module descriptor
JRebel distribution
Dependencies
Plugin itself

49. Maven Build
• NetBeans modules maven plugin
– nbm-maven-plugin
• Properties maven plugin
– properties-maven-plugin
• Maven dependency plugin
– maven-dependency-plugin
• Maven compiler plugin
• Maven JAR plugin

50. Publishing
• http://plugins.netbeans.org/
• Verification is performed manually (by
volunteers)
• Main criteria: should not break the platform
• Takes some time

51. Lessons Learned
• UX is hard
• Follow the logic of the target IDE
• Follow the new APIs
• Annotations over layer.xml
• If no required extension point provided, can
get around with patching via ModuleInstall
• Publishing is not 100% predictable process

52. Credits
• Big thanks to NetBeans team for awesome co-
operation & providing the new API for
debugger and server adaptors!