Comments on: Amazing Caching Proxy in Java

By: cheind

cheind — Sat, 27 Dec 2008 10:28:06 +0000

hi martin & merry christmas,

you might consider some features of the memcache library for ruby (i.e. expiration you’ll need sooner or later). Here’s an application quite the same as yours http://refactormycode.com/codes/609-caching-methods.

Joined github? Can anyone here my echooooooo?

By: Anonymous

Anonymous — Thu, 25 Dec 2008 20:11:25 +0000

This is not thread safe (HashMap has to be synchronized).
That’ll make it potentially much slower in a multi-threaded application. ConcurrentHashMap might help.

- Anon

By: Martin Ankerl

Martin Ankerl — Thu, 25 Dec 2008 10:58:48 +0000

thanks for the link, Jim!

By: Jim White

Jim White — Thu, 25 Dec 2008 05:55:13 +0000

This is already a widely known technique called memoization.

http://en.wikipedia.org/wiki/Memoization

Heh, just looked at the Java implementation link, and it is this same proxy method published five years ago.

http://www.onjava.com/pub/a/onjava/2003/08/20/memoization.html

By: fede

fede — Wed, 24 Dec 2008 23:15:18 +0000

public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable {
final Args input = new Args(method, args);
Result result = argsToOutput.get(input);
if (result==null) {
result= new Result(method.invoke(code, args));
argsToOutput.put(input, result);
}
return result.getValue();
};

By: Martin Ankerl

Martin Ankerl — Wed, 24 Dec 2008 20:13:14 +0000

Hi ben, good points! I have never used referencemap before. And if it returns null it always recalculates. I could use containsKey but then I need two lookups, one for contains and one to get the element. Merry christmas!

By: ben

ben — Wed, 24 Dec 2008 20:02:01 +0000

Improvements:

1. Use a referencemap
2. What happens if there is a large running process that returns null?

Merry xmas