Third party library in jenkins plugin

[silkperformer]

I need to use a library installed on slave.

Till JDK8 I used a hack to load this library:

ClassLoader clsLoader = ClassLoader.getSystemClassLoader();
if (URLClassLoader.class.isInstance(clsLoader))
{
File ff = new File(pahtToJarFile.jar);
Method method = URLClassLoader.class.getDeclaredMethod("addURL",
URL.class);
method.setAccessible(true);
method.invoke(ClassLoader.getSystemClassLoader(),
ff.toURI().toURL());
}

But in JDK11 it is not working anymore.

Is there a way to add a jar installed on the slave to the classpath using
Jenkins configuration?



--
Sent from: http://jenkins-ci.361315.n4.nabble.com/Jenkins-dev-f387835.html

[Jesse Glick]

On Fri, Jan 24, 2020 at 10:36 AM silkperformer
<silkpe...@microfocus.com> wrote:
> I need to use a library installed on slave.
>
> Till JDK8 I used a hack to load this library:

Do not do that in any version.

> Is there a way to add a jar installed on the slave to the classpath

No; you may create a _new_ `URLClassLoader` and load classes from it
reflectively.

[silkperformer]

Yes, but I have to implement a listener from this library.

[Jesse Glick]

On Fri, Jan 24, 2020 at 10:49 AM silkperformer
<silkpe...@microfocus.com> wrote:
> Yes, but I have to implement a listener from this library.

You can split your plugin into three JARs (e.g., Maven modules in a reactor):

· Some interfaces encapsulating how you wish to work with the library
but without referring to any of its types, or your plugin’s types.
· An implementation of those interfaces, depending on the first JAR as
well as some minimal supported version of the library you expect to
find (I am presuming it is versioned compatibly).
· Your plugin, depending on the first JAR, and bundling the second JAR
as a _resource_ (not a dependency).

The plugin would then create a `URLClassLoader` containing the first
and second JARs plus the actual library location on the agent, load
the implementation class by name, cast it to the interface type, and
work with it.

The Maven complexity of all this is worth it if your interfaces are
extensive. If you just need to call a couple methods from the library,
it is easier to do that using reflection. If you need to implement a
listener _interface_, you can do that via `Proxy`. If it is an
abstract class, then things get trickier as you would need to use ASM
or the to create a dynamic subclass.

Also consider just interacting with the library via a command-line
interface rather than trying to link against it at the Java level.