Re: Loading plugins

Lew <>
Thu, 07 Oct 2010 00:08:17 -0400
markspace wrote:

3. Use the existing mechanisms.

Java Jar files allow you to set a classpath in the Jar file itself. Then
the system class loader will also load class files or Jar files from
that path. This path is always relative to your Jar file, so this makes
for a convenient way to allow for extensions.

It's not well explained here but you also have access to paths like
/plugin/* which will load any Jar in the sub-directory /plugin which is
in the same directory as your Jar file.

This, however, will not work from JAR manifests, according to the documentation.


"Understanding class path wildcards"
"However, class path wildcards are not honored in the Class-Path jar-manifest

Spud wrote:

Thanks. I had no idea this existed. I've googled around and haven't

You really should be aware of the tutorials, at a minimum.

found better documentation on what the manifest class-path entry does.
Do you know if there is an official specification for manifest syntax

Start here for all official Java documentation:

Click on the little box that says "jar".

 From there, click on the link that says, "Specification - The JAR File

 From there click on the link that says, "JAR Manifest"

In particular, I'd like to know if I can recurse into all the
sub-subdirectories. The /plugin/* solution is nice, but I can get the
same result if I add "-jar /plugin/*" to the java [sic] command line. It

Huh? Well, if by "same result" you mean "it doesn't work", sure.

The command "java -jar /plugin/*" will run only the first JAR file found by
the expansion of the shell wildcard, and feed the names of the rest to it as
arguments, surely not what you intend.

Remember, if you use the "-jar" option, NOTHING else on the command line
influences the classpath.

doesn't touch any subdirectories of /plugin, though.

OK. It doesn't do what you want in any event, so it hardly matters.


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