sinistral.sourcery

As a self-confessed command-line junkie, the amount of work that is required to start a Java application has always bothered me.  The command-line for any application that requires more than one or two .jar files or class file directories to be specified quickly becomes a nightmare to type, and one very often has to resort to a shell script.  While I have no problem with shell scripts per se, it seems only slightly less inconvenient to write a shell script for every application (with its own unique classpath) that I want to run, than it is to type the command-line for that application (especially when writing throwaway test classes).

As a first step to reducing the overhead involved in setting up a classpath, I have written a class loader that is able to read the classpath elements from a (set of) files.

Each line in the file must represent either a directory or .jar file that would normally be added using the -classpath switch.  One can also use a #include directive to specify a directory that must be searched (non-recursively) for .jar files that must be added to the classpath. If the #import directive to include a regular file, that file will be read as a classpath file. For example, a classpath file may look something like:

#include /usr/local/lib/javalibdir
#include /home/user/directory/.classpathfile
/some/relative/directory/lib.jar

The initial classpath file is specified using the system property tierseven.cfcl.ClasspathFileClassLoader.file and the system property tierseven.cfcl.ClasspathFileClassLoader.verbose may be used to activate debug output. The class loader itself should be installed as the system class loader by using the system property java.system.class.loader. For example:

java -Djava.system.class.loader=tierseven.cfcl.ClasspathFileClassLoader -Dtierseven.cfcl.ClasspathFileClassLoader.file=.classpath -classpath . <main_class> <cmd_line_parameters>

This is still really much longer than i’d like it to be (mostly because of the properties) but at least this can be used in a generic shell script that can be used to start any application (if the classpath file location is parameterised).The source is available under the BSD license and is a work in progress.