[Joelib-devel] Libraries and Java versions

[Peter Murray-R. <pm...@ca...>]

[Crossposted to several lists - suggest we only reply on CDK]

We are about to release JUMBO4.6 - effectively a major release - but came 
across two problems which we think need communal agreement. It affects most 
of the Java Open Source community. I suggest we reply ONLY on CDK to limit 
traffic

We develop on both Java 1.4 and 1.5 and discovered yesterday that byte code 
*compiled on 1.5* will not run on 1.4 systems (even simple programs like 
HelloWorld). It fails with an incompatible version number (actually 
requires version 49.0 (sic) of Java). Therefore if we compiled and released 
JUMBO on 1.5 machines it would fail anywhere with 1.4. [We assume that J1.4 
bytecode runs on 1.5 systems]

Q. what strategy do the various groups have for this? Do you have any idea 
of the rate of take up of J1.5?

javac 1.5 has a switch -target 1.4 which we assume generates byte code 
compatible with J1.4 systems.

Q does this work?

Q. have you used and deployed code of this sort?

Q is it a good strategy?

Q should our community (Jmol, JCP, CDK, QSAR, Octet, JOElib, JUMBO) have a 
communal view? If we all do the same thing we are limited by the slowest. I 
assume that Jmol, for example, need to retain considerable backward 
compatibility

=========================

We have also now developed a large communal library. Thus JUMBO includes 
Jmol, JCP, CDK and therefore all their libraries. (We are delighted with 
this functionality - Billy has a very nice CML document viewer based on 
this) However...
  This can mean 2 or even 3 copies of things like Xerces in the distrib. 
The size is bad enough but since Xerces is now in the JVM 1.5 and also 
seems to change its signatures with every new moon the chance of 
incompatible versions is high. There are also copies of CDK libraries in 
JCP and so on.

We also found that when we installed a recent CDK a method in CDK had 
disappeared which led to a compilation problem - we've managed to kludge 
round but this will be an ongoing problem.  Whenever there is a new (even 
minor) release of any of our libraries we all have to clean and rebuild in 
case of these problems.

Q How do we manage our libraries? If all of us use everyone else's 
libraries then these problems will increase. For example we'd like to use 
JOELib but not necessarily as part of our distributed system. If the 
performance is not time-critical then we can use web services as a means of 
insulating the APIs and libraries. For example we might move to running a 
CDK 2Dlayout server. This could be distributed so that connections to the 
web wouldn't be needed. However it would necessarily increase the 
complexity and is incompatible with, say, lightweight applets.

P.


Peter Murray-Rust
Unilever Centre for Molecular Informatics
Chemistry Department, Cambridge University
Lensfield Road, CAMBRIDGE, CB2 1EW, UK
Tel: +44-1223-763069