pl.ais.commons.bean.facade.Facade Maven / Gradle / Ivy
package pl.ais.commons.bean.facade;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Enhancer;
import org.objenesis.ObjenesisHelper;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import static pl.ais.commons.bean.facade.ClassPredicates.inheritable;
import static pl.ais.commons.bean.facade.ClassPredicates.is;
/**
* Provides set of methods usable for creating facades.
*
* @author Warlock, AIS.PL
* @since 1.0.1
*/
@Immutable
public final class Facade {
private Facade() {
throw new AssertionError("Creation of " + getClass().getName() + " instances is forbidden.");
}
private static Class determineSuperclass(@Nonnull final Class candidate) {
return is(candidate, inheritable()) ? candidate : determineSuperclass(candidate.getSuperclass());
}
/**
* Creates and returns the facade (proxy) built over given instance of class {@literal T}.
*
* @param instance instance to be proxied
* @param listener property traverse listener to be used for the facade
* @param superclass of {@literal T} which will be extended by the facade
* @param type of the instance to be proxied
* @return newly created facade (proxy) build over given instance of class {@literal T}
*/
@SuppressWarnings("unchecked")
public static S over(@Nonnull final T instance, final TraverseListener listener) {
// Create CGLIB Enhancer using the instance class as superclass of the proxy we intend to create, ...
final Class superclass = determineSuperclass((Class) instance.getClass());
final Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(superclass);
// ... specify set of interfaces to be implemented by the proxy, ...
enhancer.setInterfaces(superclass.isInterface() ? new Class[] {superclass} : superclass.getInterfaces());
// ... define the type of callback to be used, ...
enhancer.setCallbackType(DelegatingMethodInterceptor.class);
// ... and created the proxied class (skipping creating the instance for now).
final Class proxiedClass = enhancer.createClass();
// Now prepare to create an instance of the proxied class, register callbacks and the class loader, ...
Enhancer.registerCallbacks(proxiedClass, new Callback[] {new DelegatingMethodInterceptor(instance, listener)});
enhancer.setClassLoader(superclass.getClassLoader());
// ... and do the dirty work.
return ObjenesisHelper.newInstance(proxiedClass);
}
}