private TemplateModel getInternal(String key)
throws TemplateModelException, ClassNotFoundException {
{
TemplateModel model = (TemplateModel) cache.get(key);
if (model != null) return model;
}
final ClassIntrospector classIntrospector;
int classIntrospectorClearingCounter;
final Object sharedLock = wrapper.getSharedIntrospectionLock();
synchronized (sharedLock) {
TemplateModel model = (TemplateModel) cache.get(key);
if (model != null) return model;
while (model == null && classIntrospectionsInProgress.contains(key)) {
// Another thread is already introspecting this class;
// waiting for its result.
try {
sharedLock.wait();
model = (TemplateModel) cache.get(key);
} catch (InterruptedException e) {
throw new RuntimeException("Class inrospection data lookup aborded: " + e);
}
}
if (model != null) return model;
// This will be the thread that introspects this class.
classIntrospectionsInProgress.add(key);
// While the classIntrospector should not be changed from another thread, badly written apps
// can do that,
// and it's cheap to get the classIntrospector from inside the lock here:
classIntrospector = wrapper.getClassIntrospector();
classIntrospectorClearingCounter = classIntrospector.getClearingCounter();
}
try {
final Class clazz = ClassUtil.forName(key);
// This is called so that we trigger the
// class-reloading detector. If clazz is a reloaded class,
// the wrapper will in turn call our clearCache method.
// TODO: Why do we check it now and only now?
classIntrospector.get(clazz);
TemplateModel model = createModel(clazz);
// Warning: model will be null if the class is not good for the subclass.
// For example, EnumModels#createModel returns null if clazz is not an enum.
if (model != null) {
synchronized (sharedLock) {
// Save it into the cache, but only if nothing relevant has changed while we were outside
// the lock:
if (classIntrospector == wrapper.getClassIntrospector()
&& classIntrospectorClearingCounter == classIntrospector.getClearingCounter()) {
cache.put(key, model);
}
}
}
return model;
} finally {
synchronized (sharedLock) {
classIntrospectionsInProgress.remove(key);
sharedLock.notifyAll();
}
}
}
