Grails not loading classes in .jar file

I am interested in using a certain library (Gremlin, the graph traversal language) in my Grails project. I dropped the necessary .jars into [grailsproject]/lib. But when I do grails run-app it gives me a compilation error re:a class 'Gremlin' which is part of the jar (I confirmed that it is included in the jar by running tar tf <jarfile>.jar, and it shows the class Gremlin):

[groovyc] org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed,
...unexpected token: Gremlin @ line 45, column 2.
  [groovyc]     Gremlin.load()
  [groovyc]     ^

Is there a way to "refresh" Grails to make sure it loads the new jar files? I use the exact same jar in an independent groovy test app with the same import statements, and there I am able to use the Gremlin class and it works fine. My system $CLASSPATH doesn't include any jar files that I haven't also added in [grailsproject]/lib.

Any ideas?

Thanks!

Update: Here's the relevant section from the code:

package com.mycompany.myproject

import org.codehaus.groovy.grails.commons.ConfigurationHolder as CH
import com.orientechnologies.common.collection.*
import com.orientechnologies.common.*
import com.orientechnologies.orient.core.*
import com.tinkerpop.blueprints.*
import com.tinkerpop.blueprints.pgm.*
import com.tinkerpop.blueprints.pgm.impls.orientdb.*
import com.tinkerpop.gremlin.pipes.*
import com.tinkerpop.gremlin.Gremlin
import co开发者_如何学JAVAm.tinkerpop.gremlin.*


class GraphDbService {

    boolean transactional = true    

    Gremlin.load()

    ...

I think you have to put Gremlin.load() inside a method, not just in the definition section of your service class...

ie:

class GraphDbService {
  boolean transactional = true    

  def someServiceMethod() {
    Gremlin.load()
  }

  ...

Or, preferably, you should be able to put it in the init() method of your BootStrap.groovy file, as it only needs calling once , so that it can decorate all of the required classes.

I think you should be able to add the following to the grails-app/conf/BuildConfig.groovy

grails.project.dependency.resolution = {
    //...bunch of stuff
    dependencies {
        // other resolved dependencies here

        compile files('lib/gremlim.jar')
    }
}

Do

grails compile --refresh-dependencies