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From Peter Firmstone <j...@zeus.net.au>
Subject River Core Platform [was: Re: sketches]
Date Sat, 06 Feb 2010 23:19:38 GMT
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 

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 

      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 

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)


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:jini@zeus.net.au] 
> Sent: Friday, February 05, 2010 5:16 PM
> To: river-dev@incubator.apache.org
> 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.

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