Christopher Dolan wrote:
Honest question: considering that Sun end-of-lifed Java 1.5 back in
October 2009, what's the value in continuing to support the Java 1.4
platform in River?
Honest Answer: Just a few billion blue ray players, set top boxes and
multifunction network printers and any other device that run Java cdc.
Let me make one thing very clear: No code will be rejected because it
uses a later JAVA version.
What we do need to define is what constitutes the core platform, so that
when I want to run River on a cdc device, that provides or consumes a
simple service, I can. Which again highlights another problem,
modularity, the Jini Specification is supposed to be able to have
multiple implementations.
I receive an endless stream of resistance about modularity, or
versioning, every time I try to get the blessing of the River dev list
to start working towards something, so here I sit doing the menial
tasks, getting out the new release, posting discussions to river-dev,
hesitant to make changes in case it turns out to be a wast of my
valuable time. I have children and have paid work to do also. This
isn't directed at you Chris, I want to see you participate, I just
happened to pick up your thread response, it's directed at the list in
general.
Modularity allows us to have multiple implementations, if we provide a
Service that uses Java 5 language features and if it's proxy is a smart
proxy then if that smart proxy also uses Java 5 or later then it isn't
available to Java 1.4 J2SE or cdc.
However if it is a simple reflective proxy with typical classes it's
bytecode is generated dynamically at runtime.
We need a way to annotate what Java Version a Service provides, well
that's what you call modularity, it should be handled for you
automatically by the River platform, it can be annotated in
MarshalledObject.
Compatibility Checkers
Some tools used by Apache projects:
* Java
o Clirr <http://clirr.sourceforge.net//> works on binaries
o JDiff <http://jdiff.sourceforge.net/> uses sources
Once a core platform has been decided upon, then that is all we check
for Java 1.4 compatibility and those that want the Java 1.4 platform
support are obliged to maintain that compatibility, namely me, but it
was me that pushed later Java language feature support in the first
place and still support it, I want as large an adoption and user pool as
possible.
So if we put the effort into defining just what the minimum requirements
are for producing or consuming a basic service, we have the core
platform, this can then be a small download.
Eg, the JERI Relay service that Sim is working on is not part of the
core platform, why not take advantage of the Concurrency libraries?
Reggie Services shouldn't be restricted either, you wouldn't provide a
Reggie service with java cdc, however it's proxy stub would need to be
compiled with the -jsr1.4 option. (Actually Reggie still uses rmic, we
need to convert to JERI)
NO CODE WILL BE REJECTED BECAUSE IT USES LATER JAVA LANGUAGE FEATURES
If you want to prove to yourself the -jsr14 compiler option works, edit
build.xml, add the option, use JDK1.6 to compile the current codebase
and specify source=5 instead of 1.4.
I'm actually starting to wonder if we need two Releases of Apache River:
1. River for Trusted Intranet Networks
2. River for Untrusted Networks
Both could use the same core platform, one would be secure by default
and require more configuration, the other simple, with few concerns
about security, or codebase evolution (Preffered Class loading
mechanisms will suffice).
BR Peter.
I've found it to be tricky to avoid using new methods when striving for
backward runtime compatibility. Extensive unit testing or static
analysis are the only ways to ensure you've found all the problems,
since the compiler won't help you.
Googling for "-target jsr14" revealed this less-than-inspiring quote:
"It is convenient, if unsupported, and the compiler generates mostly
compatible bytecode in a single pass."
http://twit88.com/blog/2008/08/26/java-understanding-jsr14/
Chris
-----Original Message-----
From: Peter Firmstone [mailto:[email protected]]
Sent: Friday, February 05, 2010 5:16 PM
To: [email protected]
Subject: Re: sketches
Yes, Java 5 language features next release.
Although I'd like to find just what our core jini platform should be and
compile it with -jsr14 to produce Java 1.4 bytecode from Java 5 source.
In that core platform, we couldn't use any new methods or libraries not
in Java 1.4, however we could use generics.
So for instance the Java cdc platform can consume and provide simple
services.
Cheers,
Peter.
