Package org.apache.tomcat
Interface InstrumentableClassLoader
- All Known Implementing Classes:
ParallelWebappClassLoader
,WebappClassLoader
,WebappClassLoaderBase
public interface InstrumentableClassLoader
Specifies a class loader capable of being decorated with
ClassFileTransformer
s. These transformers can instrument
(or weave) the byte code of classes loaded through this class loader
to alter their behavior. Currently only
WebappClassLoaderBase
implements this
interface. This allows web application frameworks or JPA providers
bundled with a web application to instrument web application classes
as necessary.
You should always program against the methods of this interface
(whether using reflection or otherwise). The methods in
WebappClassLoaderBase
are protected by the default security
manager if one is in use.
- Since:
- 8.0, 7.0.64
-
Method Summary
Modifier and TypeMethodDescriptionvoid
addTransformer
(ClassFileTransformer transformer) Adds the specified class file transformer to this class loader.Returns a copy of this class loader without any class file transformers.void
removeTransformer
(ClassFileTransformer transformer) Removes the specified class file transformer from this class loader.
-
Method Details
-
addTransformer
Adds the specified class file transformer to this class loader. The transformer will then be able to instrument the bytecode of any classes loaded by this class loader after the invocation of this method.- Parameters:
transformer
- The transformer to add to the class loader- Throws:
IllegalArgumentException
- if the transformer is null.
-
removeTransformer
Removes the specified class file transformer from this class loader. It will no longer be able to instrument the byte code of any classes loaded by the class loader after the invocation of this method. However, any classes already instrumented by this transformer before this method call will remain in their instrumented state.- Parameters:
transformer
- The transformer to remove
-
copyWithoutTransformers
ClassLoader copyWithoutTransformers()Returns a copy of this class loader without any class file transformers. This is a tool often used by Java Persistence API providers to inspect entity classes in the absence of any instrumentation, something that can't be guaranteed within the context of aClassFileTransformer
'stransform
method.The returned class loader's resource cache will have been cleared so that classes already instrumented will not be retained or returned.
- Returns:
- the transformer-free copy of this class loader.
-