[gradle-user] Classloader issue with native code

[Thomas Fuchs]

Hi all,

I'm facing a problem using Gradle to use groovy.sql.Sql in one task
and hibernateTools in another task in the same invocation of gradle.

I'm using MsSqlServer with integratedSecurity, so for creating the
connection the dll "sqljdbc_auth.dll" is needed.

This means sqlTask uses the groovy classloader to load the
driver which loads sqljdbc_auth.dll and
hibernateToolTask uses AntClassLoader to load the same
dll. This is not possible in one JVM. A dll can only be loaded
by one classloader.

The error I see is: "Failed to load the sqljdbc_auth.dll."
The real cause is only viewable within the debugger:
"Native Library already loaded in another classloader"

Every task works perfectly if I remove the dependency
from hibernateToolTask to sqlTask and use gradle to invoke it single:
gradle sqlTask
gradle hibernateToolTask

Both together
 gradle hibernateToolTask sqlTask
result in the error.

Is there a way to resolve this issue?

Here are the two tasks:

task sqlTask() << {
 URLClassLoader loader = GroovyObject.class.classLoader
 configurations.driver.each {File file -> loader.addURL(file.toURL())}
 Class driver = loader.loadClass(dbDriver)
 Sql sql = Sql.newInstance(dbUrl)
 logger.info("Using Catalog: ${sql.getConnection().getCatalog()}")
 sql.eachRow('select * from raw.akte') { row ->
    println "${row.id} ($row.value)"
  }
  sql.close()
}

task hibernateToolTask(dependsOn: sqlTask) << {
 ant {
   taskdef(name:'hibernatetool',
     classname:'org.hibernate.tool.ant.HibernateToolTask',
        classpath: configurations.hibernateGen.asPath)
  hibernatetool {
   jdbcconfiguration( propertyfile: "$dirGeneratedResources/db.properties",
          packagename: mapper.dao',
        reversestrategy: utils.ExtendDelegatingReverseEngineeringStrategy',
        revengfile: 'src/main/resources/build/hibernate.reveng.xml')
   hbm2hbmxml (destdir: dirGeneratedHbmRaw)
   hbm2cfgxml (destdir: dirGeneratedResources)
   hbm2java   (destdir: dirGeneratedJava, jdk5:'true')
  }
 }
}
compileJava.dependsOn(hibernateToolTask)

Environement infos:
------------------------------------------------------------
Gradle 1.0-milestone-3
------------------------------------------------------------
Gradle build time: Monday, 25 April 2011 5:40:11 PM EST
Groovy: 1.7.10
Ant: Apache Ant(TM) version 1.8.2 compiled on December 20 2010
Ivy: 2.2.0
JVM: 1.6.0_16 (Sun Microsystems Inc. 14.2-b01)
OS: Windows 7 6.1 x86
Anyone got any ideas?

Thanks very much in advance for any hints!
Thomas