Re: Create Dynamic Proxy for class instead of interface

From:

Tom Anderson <twic@urchin.earth.li>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 13 Jun 2011 11:58:02 +0100

Message-ID:

<alpine.DEB.2.00.1106131149420.6141@urchin.earth.li>

On Sun, 12 Jun 2011, Stanimir Stamenkov wrote:

The Dynamic Proxy API [1] allows one to create proxy classes
implementing number of specified interfaces. I've wondered if it is
possible and how to create such a proxy class for a specified class and
not interface. I've found Javassit should provide such means, but
haven't really tried it yet:

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

I basically want to create a proxy augmenting an existing object with
additional interface. Is the Javassist library the right tool for doing
this? Are there other similar tools?

A number - i wrote a little list at one point:

http://urchin.earth.li/~twic/Java_Bytecode_Libraries.html

Having said that, while all of these can be used to do the bytecode
editing you would need to construct such a proxy, i don't know if all of
them include ready-made tools to do it. Probably not.

Something else you probably want to know about is the instrumentation API:

http://download.oracle.com/javase/6/docs/api/java/lang/instrument/package-summary.html

Essentially, you can use this to get all classes loaded by the JVM to go
through some of your code to be modified before loading. That lets you
actually rewrite existing classes as they load - no need for proxies, you
can change the actual classes. This is commonly used by things like JPA
and AOP implementations.

tom

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