grails upgrade 2.0.1 command object validation error

Question

after upgrading from grails 1.3.7 to 2.0.1 i'm getting follwong strange exception when validating command object within a controller.

  groovy.lang.GroovyRuntimeException: Ambiguous method overloading for method org.codehaus.groovy.grails.orm.hibernate.HibernateGormValidationApi#validate.
Cannot resolve which method to invoke for [class at.pdts.etsweb.commandobject.UserCommand, null] due to overlapping prototypes between:
    [class java.lang.Object, interface java.util.List]
    [class java.lang.Object, interface java.util.Map]

    at org.grails.datastore.gorm.InstanceMethodInvokingClosure.call(GormEnhancer.groovy:251)

    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)

    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)

    at java.lang.Thread.run(Thread.java:662)

My UserCommand command object looks like this:

package at.pdts.etsweb.commandobject

import at.pdts.etsweb.Common
import grails.validation.Validateable

    @Validateable
    class UserCommand { 
        String username
        String password
        String firstname
        String lastname 
        static constraints = {
            username blank: false, email: true
            password blank: false, minSize: 8, maxSize: 64, validator: Common.passwordValidator
            firstname blank: false
            lastname blank: false
        }
    }

The controller binds the data as follows:

def save { UserCommand command ->

...
}

At this point i'm getting the above error message. i tried also to use the command object as an argument save(UserCommand command), but with no effect. Does anyone have some hint?

Answer 1

My workaround was to move the command object classes from the /grails-app/controller to /src/groovy. After that the error disappeared.