Being a programmer, I would ask you to take a look at this class.
Plugin:
org.eclipse.osgi_3.10.2.v20150203-1939.jar
Class:
BundleLoader
Below 2 methods will give lot of understanding:
Class<?> findClass(String name, boolean checkParent) throws ClassNotFoundException {
if (checkParent && parent != null && name.startsWith(JAVA_PACKAGE))
// 1) if startsWith "java." delegate to parent and terminate search
// we want to throw ClassNotFoundExceptions if a java.* class cannot be loaded from the parent.
return parent.loadClass(name);
return findClassInternal(name, checkParent);
}
private Class<?> findClassInternal(String name, boolean checkParent) throws ClassNotFoundException {
if (debug.DEBUG_LOADER)
Debug.println("BundleLoader[" + this + "].findClassInternal(" + name + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
String pkgName = getPackageName(name);
boolean bootDelegation = false;
// follow the OSGi delegation model
if (checkParent && parent != null && container.isBootDelegationPackage(pkgName))
// 2) if part of the bootdelegation list then delegate to parent and continue of failure
try {
return parent.loadClass(name);
} catch (ClassNotFoundException cnfe) {
// we want to continue
bootDelegation = true;
}
Class<?> result = null;
try {
result = (Class<?>) searchHooks(name, PRE_CLASS);
} catch (ClassNotFoundException e) {
throw e;
} catch (FileNotFoundException e) {
// will not happen
}
if (result != null)
return result;
// 3) search the imported packages
PackageSource source = findImportedSource(pkgName, null);
if (source != null) {
if (debug.DEBUG_LOADER) {
Debug.println("BundleLoader[" + this + "] loading from import package: " + source); //$NON-NLS-1$ //$NON-NLS-2$
}
// 3) found import source terminate search at the source
result = source.loadClass(name);
if (result != null)
return result;
throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$
}
// 4) search the required bundles
source = findRequiredSource(pkgName, null);
if (source != null) {
if (debug.DEBUG_LOADER) {
Debug.println("BundleLoader[" + this + "] loading from required bundle package: " + source); //$NON-NLS-1$ //$NON-NLS-2$
}
// 4) attempt to load from source but continue on failure
result = source.loadClass(name);
}
// 5) search the local bundle
if (result == null)
result = findLocalClass(name);
if (result != null)
return result;
// 6) attempt to find a dynamic import source; only do this if a required source was not found
if (source == null) {
source = findDynamicSource(pkgName);
if (source != null) {
result = source.loadClass(name);
if (result != null)
return result;
// must throw CNFE if dynamic import source does not have the class
throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$
}
}
if (result == null)
try {
result = (Class<?>) searchHooks(name, POST_CLASS);
} catch (ClassNotFoundException e) {
throw e;
} catch (FileNotFoundException e) {
// will not happen
}
// do buddy policy loading
if (result == null && policy != null)
result = policy.doBuddyClassLoading(name);
if (result != null)
return result;
// hack to support backwards compatibility for bootdelegation
// or last resort; do class context trick to work around VM bugs
if (parent != null && !bootDelegation && ((checkParent && container.getConfiguration().compatibilityBootDelegation) || isRequestFromVM()))
// we don't need to continue if a CNFE is thrown here.
try {
return parent.loadClass(name);
} catch (ClassNotFoundException e) {
// we want to generate our own exception below
}
throw new ClassNotFoundException(name + " cannot be found by " + this); //$NON-NLS-1$
}
Resources:
http://moi.vonos.net/java/osgi-classloaders/
