[Engine-devel] Improve classpath building

[Oved Ourfalli]

----- Original Message -----
> From: "Juan Hernandez" <jhernand at redhat.com>
> To: engine-devel at ovirt.org
> Sent: Tuesday, June 5, 2012 3:53:08 PM
> Subject: [Engine-devel] Improve classpath building
> 
> Hello all,
> 
> I would like to propose an improvement in the way we build
> class-paths
> in the tools associated to the engine. At the moment we have at least
> two different ways to build classpaths:
> 
> 1. Hard coded in the scripts, with maybe some variables:
> 
> CP=$EAR_LIB/engine-encryptutils.jar:$EAR_LIB/engine-compat.jar:...
> 
> This depends a lot on where we place the jar files, and we need to
> place
> them in different places in different environments if we want to
> adhere
> to common packaging practices.
> 
> 2. Use the build-classpath script:
> 
> CP=`build-classpath engine-encryptutils engine-compat ...`
> 
> This depends less on the place we put them, but it doesn't work in
> development environments where some jars are not installed to the
> proper
> system locations.
> 
> None of these is good for all environments.
> 
> I would like to replace this classpath building logic with an script
> that performs the task in an smarter way and that works in all our
> environments (production, development, Fedora, RHEL, etc).
> 

In general it looks like a very good idea.
Running the utilities in a development environment today is a real pain, so such a change will save a lot of time both when setting the development environment, and when testing changes. 

Didn't review all the whole source code, but from a quick glance I saw the preferredJars dictionary. 
IMO it is better to put this configuration in a configuration file, instead of a dictionary.
Also, I would allow to change the path to this file, to allow developers to create a custom file (if they need one).

> My proposal is to create a "engine-java" script that we should use
> always when invoking java programs. This script will receive the same
> parameters that the "java" launcher receives, but the "-cp" or
> "-classpath" options will contain not the absolute name of the jar
> files, but just a simple jar name instead, something like
> "commons-logging", "commons-codec" or "engineencryptutils". The
> script
> will extract the "-cp" or "-classpath" options given and use them to
> do
> a search of the jar files in the locations where they can be in
> different environments:
> 
> /usr/share/java
> /usr/share/java/ovirt-engine
> /usr/share/ovirt-engine/engine.ear
> /usr/share/ovirt-engine/engine.ear/lib
> <your jboss development installation>/engine.ear
> <your jboss development installation>/engine.ear/lib
> 
> In addition the script will check that all the give jar files exist
> and
> will abort the execution if any of them is missing.
> 
> Find attached the initial version of the proposed script.
> 
> Let me know what you think.
> 
> Regards,
> Juan Hernandez
> 
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