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SO I am trying to redefine a class. I have a class named folder. In OSGi (using Felix) I have a new Folder class with the same methods but some additional logging.

I am trying to take the Folder Class from Felix and redefine the main Folder class on the main classloader

I do have the agent set on startup. 

new ByteBuddy()
                        .redefine(Class.forName(classToOverride.trim()), ClassFileLocator.ForClassLoader.of(felixClassLoader))
                        .name(classToOverride.trim())
                        .make()                            .load(contextClassLoader);

I have tried different strategies in the load method.

Without any strategies I get the following error

Caused by: java.lang.IllegalStateException: Cannot inject already loaded type: class com.dotmarketing.portlets.folders.model.Folder
at net.bytebuddy.dynamic.loading.ClassInjector$UsingReflection.inject(ClassInjector.java:187) ~[byte-buddy-1.6.12.jar:?]
at net.bytebuddy.dynamic.loading.ClassLoadingStrategy$Default$InjectionDispatcher.load(ClassLoadingStrategy.java:187) ~[byte-buddy-1.6.12.jar:?]
at net.bytebuddy.dynamic.loading.ClassLoadingStrategy$Default.load(ClassLoadingStrategy.java:120) ~[byte-buddy-1.6.12.jar:?]
at net.bytebuddy.dynamic.TypeResolutionStrategy$Passive.initialize(TypeResolutionStrategy.java:79) ~[byte-buddy-1.6.12.jar:?]
at net.bytebuddy.dynamic.DynamicType$Default$Unloaded.load(DynamicType.java:4376) ~[byte-buddy-1.6.12.jar:?]
at com.dotmarketing.osgi.GenericBundleActivator.publishBundleServices(GenericBundleActivator.java:177) ~[dotcms_4.1.0_563a5c3.jar:?]

With ClassReloadingStrategy.fromInstalledAgent I get no error but doesn't work.

Jason Tesser
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1 Answers1

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On a JVM, you cannot simply redefine an already loaded class. You can only redefine a class using a Java agent where Byte Buddy supplies the AgentBuilder API which you can use. Note that it is only possible to change the content of methods but not a class's layout. You probably want to have a look at the Advice API to do so.

Rafael Winterhalter
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