Using Java based Jelly TagLibrary impls that are in a Plugin

[Tom Fennelly]

Hi.

Just wondering if anyone can guide me as to how I can write a Java based TagLibrary and have it loadable from a plugin (without setting pluginFirstClassLoader=true).  When I try it I get a classloader exception that makes total sense to me, but I'm wondering if there's some trick or different impl that works around it.

Example... a Simple TagLibrary impl like this... 

public class IconsTaglib extends TagLibrary {

    public IconsTaglib() {

             // Register some tags...

        registerTag("myFunkyTag", MyFunkyTag.class);

    }

}

This class is located in the plugin i.e. not in Jenkins core with other taglibs.

Then in a .jelly tag script (also in the plugin, but for which there are no cloassloading issues) we use the myFunkyTag tag that was implemented in Java e.g.

<myf:myFunkyTag xmlns:myf="jelly:org.jenkins.x.y.MyFunkyTag" />

The above causes a ClassLoading exception because Jelly's XMLParser class (code located in Jenkins - not in the plugin) tries to load the MyFunkyTag class with the wrong classloader (XMLParser line #1024).  What looks like would work (in this specific case at least) is if XMLParser tried using the JellyContext ClassLoader instead, but of course that might cause other issues.

BTW I tried with the MyFunkyTag impl located in Jenkins core and everything works fine as expected.

Any suggestions?  I'm wondering maybe this is not an issue if I implement the Tag in Groovy instead, but would like to know if doing it in Java is not going to work first.

Thanks,

Tom.

[Tom Fennelly]

I grep'd across all repos in https://github.com/jenkinsci and apart from in jenkins and jelly, there are no Java impls of TagLibrary.  So, looks like this is not common, or maybe is never done.

[Stephen Connolly]

Do you inform jenkins that you have a taglibrary?

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[Tom Fennelly]

xmlns:myf="jelly:org.jenkins.x.y.MyFunkyTag" is one way of doing that and, as I said, that works when the TagLibrary impl is located in Jenkins core (Vs out in a plugin).  I didn't see any other way of doing it.  Are you telling me there is another way?

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[Stephen Connolly]

Well I suspect that you need to inform jelly of the TagLibrary class or else it will not discover it. I am suspecting that there is a plugin goal putting the requisite info somewhere on the classpath. That plugin goal is probably working for jenkins core but perhaps not by default in plugins

[Stephen Connolly]

I suspect one thing could be that your class name is IconsTaglib and not IconsTagLib

[Stephen Connolly]

Also you probably need to add the annotation

@org.kohsuke.stapler.jelly.groovy.TagLibraryUri("/shim/layout")

[Stephen Connolly]

Hmmm you might have to have the namespace be the FQCN of the TagLibrary implementation, eg see MorphTagLibrary in core... digging some more

[Stephen Connolly]

can you share your git repos with me so I can debug a little... or pop into hipchat and we can chat and bring the solution back to the list once we have one ;-)

[Tom Fennelly]

I'm using the name consistently - the name was resolvable when in core.

I tried to generalize the description of the problem in the email, but forgot to rename the TagLibrary impl class to from IconsTaglib to MyFunkyTaglib.  Sorry about that... should have just left as is :)

[Tom Fennelly]

Tried that.  It didn't help.  Unless it needs to be done in conjunction with something else.

[Tom Fennelly]

Right... I'm doing that (same as with MorphTagLibrary).  And as I said, that works fine when the TagLibrary impl is in core.

<ic:setIcons xmlns:ic="jelly:org.jenkins.ui.icon.taglib.IconsTaglib" />

[Tom Fennelly]

Sure:

• Branch: https://github.com/tfennelly/jenkins/tree/icon-tag
• Taglib classes: https://github.com/tfennelly/jenkins/tree/icon-tag/icon/src/main/java/org/jenkins/ui/icon/taglib
• Use of in a .jelly script: https://github.com/tfennelly/jenkins/blob/icon-tag/icon/src/main/resources/lib/ui/icon/icon.jelly#L46
  

Thanks Stephen !!

[Stephen Connolly]

where's the example where you had it as a plugin and where is the example plugin using it?

[Tom Fennelly]

Ah yes, sorry... I checked out and changed the credentials plugin... I just pushed a branch to https://github.com/jenkinsci/credentials-plugin/tree/icon-tag-test

[Stephen Connolly]

that's using the ui:icon taglib directly...

[Tom Fennelly]

Right, and <ui:icon> is using the Java TagLibrary impl that is causing the issue (https://github.com/tfennelly/jenkins/blob/icon-tag/icon/src/main/resources/lib/ui/icon/icon.jelly#L46).

The naming is a bit confusing there atm because I was hacking something just to experiment with Java Taglib impls.  That will get cleaned up if we can get the basic thing to work.

[Tom Fennelly]

I'll simplify this for the purposes of getting to the bottom of this particular problem i.e. create a no-op Java TagLibrary impl on the credentials-plugin.  What I was playing with there is ok for me, but confusing for someone else coz there's other stuff in there that's not related to this problem.

On 03/07/2014 12:21, Stephen Connolly wrote:

[Stephen Connolly]

yeah I'm just setting up some clean plugins which can be used as a test... your hacking existing stuff is messing you up I believe

[Tom Fennelly]

Yeah... you're prob right.

[Tom Fennelly]

Okay, I created a MyFunkyTagLibrary here: https://github.com/jenkinsci/credentials-plugin/tree/java-taglib-test

So we can forget about the other stuff for now.  Sorry for the confusion.

On 03/07/2014 12:48, Stephen Connolly wrote:

[Stephen Connolly]

I have much more stripped back plugins: https://github.com/stephenc/icon-shim-plugin and https://github.com/stephenc/icon-shim-consumer-plugin

[Stephen Connolly]

I am hitting the same classloader issue you see... currently seeing if I can indirect myself around it

[Tom Fennelly]

I can't see how you'd get this to work without making changes to Jelly's XMLParser and how it selects the correct classloader to use.  On the other hand, we can do what we need to do using a groovy tag/script.