[Engine-devel] Improve classpath building

[Juan Hernandez]

On 06/05/2012 04:41 PM, Yair Zaslavsky wrote:
> On 06/05/2012 03:53 PM, Juan Hernandez wrote:
>> 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).
>>
>> 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.
>
> Excellent idea!
> I would like to add -
> I already saw the work you did on engine-manage-domains.
> When we work on development machines, we might have the jars reside in
> different places.

Yes, this is one of the motivations for this new engine-java script, the 
fact that we can't expect the build-classpath script to work in all 
environments, specially development environments.

> I wanted to create a script that will allow for example to use
> build-classpath on spring-ldap-core, but I did not have a soft link for
> that in /usr/share/java (is that what I needed to do?)

Yes, just create the link in /usr/share/java and it should work. If you 
want to keep it compatible with the Fedora spring-ldap package create it 
as "/usr/share/java/spring-ldap/spring-ldap-core.jar", then you should 
be able to use it with "build-classpath spring-ldap/spring-ldap-core".

> I guess we will have to differentiate between the need of dev and
> production for this script.

I would rather try to make it work in all the environments without 
change, but I know that is quite difficult.

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