Question

I am asking this purely to determine the worthwhile-ness of implementing the class in Question …

Do you know of a Java utility class that takes an un-synchronized instance, uses reflection to investigate that instance, and returns the input instance ‘wrapped’ within synchronized calls ?

( ie: A factory which creates a synchronized delegate class for any instance )

Answer 1

I like Jon Skeet’s answer; it’s seeing the forest instead of the trees. But to answer the question:

Assuming that the instance belongs to some interface, it’s easy to use java.lang.reflect.Proxy to do this.

public final class SynchronizedFactory {     private SynchronizedFactory() {}      public static <T> T makeSynchronized(Class<T> ifCls, T object) {         return ifCls.cast(Proxy.newProxyInstance(                 object.getClass().getClassLoader(),                 new Class<?>[] {ifCls},                 new Handler<T>(object)));     }      private static class Handler<T> implements InvocationHandler {         private final T object;          Handler(T object) {             this.object = object;         }          @Override         public Object invoke(Object proxy, Method method,                 Object[] args) throws Throwable {             synchronized (object) {                 return method.invoke(object, args);             }         }     } } 

This code is not tested, by the way. Use at your own risk.