It is easier to write shell script to import jar files by directory instead of explicitly reference to a few jars with specific versions.
The common use case is: HBase needs to use hadoop jar files, but HBase depends on more recent version of log4j. The construction of the class path would be: $HBASE_PREFIX/share/hbase/hbase*.jar:$HBASE_PREFIX/share/hbase/lib/*.jar:$HADOOP_PREFIX/share/hadoop/*.jar This provides a way to segment the library loading with least amount of scripting and loosely coupled. regards, Eric On Aug 4, 2011, at 2:40 PM, Alejandro Abdelnur wrote: > [moving to core-dev@, general@ BCCed] > > Eric, > > Even if the JAR is in lib/ you could import/use that JAR only. > > How would you use Hadoop JARs without its dependencies? Many things will > break unless you add the dependency JARs. > > Granted, there are JARs that are used by Hadoop server side only > (JT/NN/TT/DN/SNN), but that is a different thing. Having a client side set > of JARs would help handle this (MAPREDUCE-1638). > > Thoughts? > > Thanks. > > Alejandro > > On Thu, Aug 4, 2011 at 1:14 PM, Eric Yang <eric...@gmail.com> wrote: > >> The jar files placement outside of lib directory is to ensure the project >> generated jar files are not mixed with it's dependencies. >> Hence, if another project tries to import current project's jar files >> without dependencies, it is possible to do so. >> >> regards, >> Eric >> >> On Aug 4, 2011, at 11:03 AM, Alejandro Abdelnur wrote: >> >>> What is the rationale for having the hadoop JARs outside of the lib/ >>> directory? >>> >>> It would definitely simplify packaging configuration if they are under >> lib/ >>> as well. >>> >>> Any objection to it? >>> >>> Thanks. >>> >>> Alejandro >> >>
