How to expose expose a Java TagLibrary

[Jason Dillon-5]

Hi, I'm trying to figure out how to expose a Java TagLibrary from a
plugin.

Inside of my plugin, I can create a:

<define:taglib uri="myplugin">
    <define:tag name="dependency-handle">
    </define:tag>
</define:taglib>

And I can access this taglib just fine from another project.

Similarly in my plugin, I can define:

<project xmlns:local="jelly:com.whatever.jelly.MyTagLibrary">
    <local:sometag/>
</project>

And I can now access the Java TagLibrary MyTagLibrary from inside the
plugin.

But, what I am trying to do is to create a plugin which provides a set
of tags for use in other projects.

How can I expose a Java TagLibrary as if it were a <define:taglib>
inside of my plugin.jelly?

I tried using <define:jellybean>, <define:bean> with no luck.  While I
was able to get the tag to attach to the taglib, it did not allow the
tags to properly find their parent via findAncestorWithClass().

So far the only luck I have had with exposing Java TagLibraries
externally is to have the plugin nest the tags inside of a dynamic tag
created.

Is this even possible with Maven 1.0.2?  If so, could someone explain
how I can do this.

Thanks,

--jason

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[Brett Porter]

There are a couple of alternatives.

Like the artifact plugin, you can wrap the java in a "jellybean", and
use the exported tag library for that. I think this is what you
describe below as unsatisfactory.

The other alternative is to put the tag library in a JAR, add that as
a dependency on the project, and reference it like this:

xmlns:foo="jelly:com.foo.tags.FooTagLibrary"

See the Xdoc plugin for an example where it references it's own
classes to do that.

HTH,
Brett

On 6/7/05, Jason Dillon <[hidden email]> wrote:

> Hi, I'm trying to figure out how to expose a Java TagLibrary from a
> plugin.
>
> Inside of my plugin, I can create a:
>
> <define:taglib uri="myplugin">
>     <define:tag name="dependency-handle">
>     </define:tag>
> </define:taglib>
>
> And I can access this taglib just fine from another project.
>
> Similarly in my plugin, I can define:
>
> <project xmlns:local="jelly:com.whatever.jelly.MyTagLibrary">
>     <local:sometag/>
> </project>
>
> And I can now access the Java TagLibrary MyTagLibrary from inside the
> plugin.
>
> But, what I am trying to do is to create a plugin which provides a set
> of tags for use in other projects.
>
> How can I expose a Java TagLibrary as if it were a <define:taglib>
> inside of my plugin.jelly?
>
> I tried using <define:jellybean>, <define:bean> with no luck.  While I
> was able to get the tag to attach to the taglib, it did not allow the
> tags to properly find their parent via findAncestorWithClass().
>
> So far the only luck I have had with exposing Java TagLibraries
> externally is to have the plugin nest the tags inside of a dynamic tag
> created.
>
> Is this even possible with Maven 1.0.2?  If so, could someone explain
> how I can do this.
>
> Thanks,
>
> --jason
>
> ===========================================================================
> This email and any attachment(s) thereto, are intended for the use of
> the addressee(s) name herein and may contain legally privileged and or
> confidential information under applicable law. If you are not the
> intended recipient of this e-mail, you are hereby notified any
> dissemination, distribution or copying of this email, and any attachment(s)
> thereto, is strictly prohibited. If you have received this communication
> in error, please notify the sender at 415-281-2200 or via return e-mail at
> [hidden email] and permanently delete the original copy and
> any copy of any e-mail, and any printout thereof. Thank you for your
> cooperation.
>
>
>
>
>
>
>
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[Jason Dillon-5]

Thanks for the response.  I think I found the solution I was looking
for... after browsing through the define taglib sources:

Use define:bean, as in:

<define:taglib uri="myplugin">
    <define:tag name="dependency-handle"/>
    <define:bean name="mytag" className="com.foo.MyTag"/>
    <define:bean name="myparenttag" className="com.foo.MyParentTag"/>
</define:taglib>

Then override MyTag's findAncestorWithClass() as:

<snip>
protected Tag findAncestorWithClass(Class type) {
    // First try the default
    Tag tag = super.findAncestorWithClass(type);
   
    if (tag == null) {
        // Then try looking for a DynamicBeanTag
        tag = findDynamicBeanAncestorWithClass(getParent(), type);
    }
   
    return tag;
}

protected Tag findDynamicBeanAncestorWithClass(Tag parent, Class type) {
    if (parent == null) {
        return null;
    }
   
    if (parent instanceof DynamicBeanTag) {
        DynamicBeanTag tag = (DynamicBeanTag)parent;
        Object bean = tag.getBean();
        if (type.isAssignableFrom(type)) {
            return (Tag)bean;
        }
    }
   
    return findDynamicBeanAncestorWithClass(parent.getParent(), type);
}
</snip>

This will unwrap the DynamicBeanTag and allow MyTag to behave as
excepted when looking for an ancestor tag.

With this combination, I can from an external project do something like:

<project xmlns:myplugin="myplugin">
    <myplugin:myparenttag>
        <!-- can talk to myparenttag via findAncestorWithClass() -->
        <myplugin:mytag/>
    </myplugin:myparenttag>
</project>

Cheers,

--jason



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thereto, is strictly prohibited. If you have received this communication
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