org.springframework.core
Class OverridingClassLoader

java.lang.Object
  java.lang.ClassLoader
      org.springframework.core.DecoratingClassLoader
          org.springframework.core.OverridingClassLoader

Direct Known Subclasses:

SimpleInstrumentableClassLoader, SimpleThrowawayClassLoader

public class OverridingClassLoader
extends DecoratingClassLoader

ClassLoader that does not always delegate to the parent loader, as normal class loaders do. This enables, for example, instrumentation to be forced in the overriding ClassLoader, or a "throwaway" class loading behavior, where selected classes are temporarily loaded in the overriding ClassLoader, in order to load an instrumented version of the class in the parent ClassLoader later on.

Since:

2.0.1

Author:

Rod Johnson, Juergen Hoeller

Field Summary

static String[]

DEFAULT_EXCLUDED_PACKAGES Packages that are excluded by default

Constructor Summary

OverridingClassLoader(ClassLoader parent)
Create a new OverridingClassLoader for the given class loader.

Method Summary

protected boolean	isEligibleForOverriding(String className) Determine whether the specified class is eligible for overriding by this class loader.
protected byte[]	loadBytesForClass(String name) Load the defining bytes for the given class, to be turned into a Class object through a ClassLoader.defineClass(byte[], int, int) call.
protected Class	loadClass(String name, boolean resolve)
protected Class	loadClassForOverriding(String name) Load the specified class for overriding purposes in this ClassLoader.
protected InputStream	openStreamForClass(String name) Open an InputStream for the specified class.
protected byte[]	transformIfNecessary(String name, byte[] bytes) Transformation hook to be implemented by subclasses.

Methods inherited from class org.springframework.core.DecoratingClassLoader

excludeClass, excludePackage, isExcluded

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findResources, findSystemClass, getPackage, getPackages, getParent, getResource, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_EXCLUDED_PACKAGES

public static final String[] DEFAULT_EXCLUDED_PACKAGES

Packages that are excluded by default

Constructor Detail

OverridingClassLoader

public OverridingClassLoader(ClassLoader parent)

Create a new OverridingClassLoader for the given class loader.

Parameters:

parent - the ClassLoader to build an overriding ClassLoader for

Method Detail

loadClass

protected Class loadClass(String name,
                          boolean resolve)
                   throws ClassNotFoundException

Overrides:

loadClass in class ClassLoader

Throws:

ClassNotFoundException

isEligibleForOverriding

protected boolean isEligibleForOverriding(String className)

Determine whether the specified class is eligible for overriding by this class loader.

Parameters:

className - the class name to check

Returns:

whether the specified class is eligible

See Also:

DecoratingClassLoader.isExcluded(java.lang.String)

loadClassForOverriding

protected Class loadClassForOverriding(String name)
                                throws ClassNotFoundException

Load the specified class for overriding purposes in this ClassLoader.

The default implementation delegates to ClassLoader.findLoadedClass(java.lang.String), loadBytesForClass(java.lang.String) and ClassLoader.defineClass(byte[], int, int).

Parameters:

name - the name of the class

Returns:

the Class object, or null if no class defined for that name

Throws:

ClassNotFoundException - if the class for the given name couldn't be loaded

loadBytesForClass

protected byte[] loadBytesForClass(String name)
                            throws ClassNotFoundException

Load the defining bytes for the given class, to be turned into a Class object through a ClassLoader.defineClass(byte[], int, int) call.

The default implementation delegates to openStreamForClass(java.lang.String) and transformIfNecessary(java.lang.String, byte[]).

Parameters:

name - the name of the class

Returns:

the byte content (with transformers already applied), or null if no class defined for that name

Throws:

ClassNotFoundException - if the class for the given name couldn't be loaded

openStreamForClass

protected InputStream openStreamForClass(String name)

Open an InputStream for the specified class.

The default implementation loads a standard class file through the parent ClassLoader's getResourceAsStream method.

Parameters:

name - the name of the class

Returns:

the InputStream containing the byte code for the specified class

transformIfNecessary

protected byte[] transformIfNecessary(String name,
                                      byte[] bytes)

Transformation hook to be implemented by subclasses.

The default implementation simply returns the given bytes as-is.

Parameters:

name - the fully-qualified name of the class being transformed

bytes - the raw bytes of the class

Returns:

the transformed bytes (never null; same as the input bytes if the transformation produced no changes)