# Custom driver has No ClassDefFoundError; works on Ignition V8.1.24 but fails in V8.1.27 + **URL:** \ **Category:** Module Development\ **Created:** [March 11, 2024, 6:43pm UTC](https://forum.inductiveautomation.com/t/custom-driver-has-no-classdeffounderror-works-on-ignition-v8-1-24-but-fails-in-v8-1-27/87147 "2024-03-11T18:43:43Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Amazon\_MAP\_Team](https://avatars.discourse-cdn.com/v4/letter/a/a88e4f/32.png) [@Amazon\_MAP\_Team](https://forum.inductiveautomation.com/u/Amazon_MAP_Team)\ **Post date:** [March 11, 2024, 6:43pm UTC](https://forum.inductiveautomation.com/t/custom-driver-has-no-classdeffounderror-works-on-ignition-v8-1-24-but-fails-in-v8-1-27/87147/1 "2024-03-11T18:43:43Z")
Hello Team, We have a custom driver module created for a particular MHE ; and this is working fine on our current fleet version of Ignition V8.1.24. We are in the process of upgrading to the minor revision V8.1.3+; and this particular driver which works well on the 8.1.24 fails with a error of Couldnot initialise class. We think we are missing some api s on the newer sdk; is that the case? How could we make this module suitable for the latest Ignition version. Thanks, Amazon MAP Team ```auto java.lang.NoClassDefFoundError: Could not initialize class com.amazon.rme.castalia.driver.DematicSC3XopcDriver at com.amazon.rme.castalia.driver.DematicSC3XopcDriverType.createDriver([DematicSC3XopcDriverType.java:112](http://dematicsc3xopcdrivertype.java:112/)) at com.inductiveautomation.ignition.gateway.opcua.server.DriverAdapter$DriverAddressSpace.startup(DriverAdapter.kt:146) at com.inductiveautomation.ignition.gateway.opcua.server.DriverAdapter.startup(DriverAdapter.kt:82) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceAddressSpace.startup(DeviceManager.kt:443) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager.createAndStartupDevice(DeviceManager.kt:236) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager.access$createAndStartupDevice(DeviceManager.kt:52) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceSettingsRecordListener$recordUpdated$1.invokeSuspend(DeviceManager.kt:397) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) ava.lang.ExceptionInInitializerError: null at com.amazon.rme.castalia.driver.DematicSC3XopcDriver.(DematicSC3XopcDriver.java:174) at com.amazon.rme.castalia.driver.DematicSC3XopcDriverType.createDriver(DematicSC3XopcDriverType.java:112) at com.inductiveautomation.ignition.gateway.opcua.server.DriverAdapter$DriverAddressSpace.startup(DriverAdapter.kt:146) at com.inductiveautomation.ignition.gateway.opcua.server.DriverAdapter.startup(DriverAdapter.kt:82) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceAddressSpace.startup(DeviceManager.kt:443) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager.createAndStartupDevice(DeviceManager.kt:236) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager.access$createAndStartupDevice(DeviceManager.kt:52) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceSettingsRecordListener$recordAdded$1.invokeSuspend(DeviceManager.kt:317) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106) at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:274) at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:85) at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59) at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source) at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38) at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceSettingsRecordListener.recordAdded(DeviceManager.kt:316) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManager$DeviceSettingsRecordListener.recordAdded(DeviceManager.kt:314) at com.inductiveautomation.ignition.gateway.localdb.PersistenceInterfaceImpl.notifyRecordAdded(PersistenceInterfaceImpl.java:168) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl.doNotifyRecordAdded(RedundantPersistenceInterfaceImpl.java:98) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordUpdateListener.recordAdded(RedundantPersistenceInterfaceImpl.java:398) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordAddedMessage.notify(RedundantPersistenceInterfaceImpl.java:474) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordUpdateListener.receiveCall(RedundantPersistenceInterfaceImpl.java:390) at com.inductiveautomation.ignition.gateway.redundancy.QueueableMessageReceiver.receiveCall(QueueableMessageReceiver.java:47) at com.inductiveautomation.ignition.gateway.redundancy.RedundancyManagerImpl.dispatchMessage(RedundancyManagerImpl.java:1042) at com.inductiveautomation.ignition.gateway.redundancy.RedundancyManagerImpl$ExecuteTask.run(RedundancyManagerImpl.java:1110) at com.inductiveautomation.ignition.common.execution.impl.BasicExecutionEngine$ThrowableCatchingRunnable.run(BasicExecutionEngine.java:544) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.base/java.util.concurrent.FutureTask.run(Unknown Source) at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source) Caused by: java.lang.IllegalStateException: java.lang.NoSuchMethodException: org.eclipse.milo.opcua.stack.core.types.builtin.Variant.(java.lang.String) at com.rme.xopcutil.nodes.NodeDataType.getVariantConstructor(NodeDataType.java:111) at com.rme.xopcutil.nodes.NodeDataType.createWithTransformer(NodeDataType.java:87) at com.rme.xopcutil.nodes.NodeDataType.(NodeDataType.java:28) ... 33 common frames omitted Caused by: java.lang.NoSuchMethodException: org.eclipse.milo.opcua.stack.core.types.builtin.Variant.(java.lang.String) at java.base/java.lang.Class.getConstructor0(Unknown Source) at java.base/java.lang.Class.getConstructor(Unknown Source) at com.rme.xopcutil.nodes.NodeDataType.getVariantConstructor(NodeDataType.java:100) ... 35 common frames omitted ``` ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [March 11, 2024, 7:35pm UTC](https://forum.inductiveautomation.com/t/custom-driver-has-no-classdeffounderror-works-on-ignition-v8-1-24-but-fails-in-v8-1-27/87147/2 "2024-03-11T19:35:57Z")
This means the static initializer of your driver class is throwing an uncaught Exception. It looks like the root of it is this: ```auto Caused by: java.lang.NoSuchMethodException: org.eclipse.milo.opcua.stack.core.types.builtin.Variant.(java.lang.String) ``` The Variant constructor(s) did not change any time recently, so it may have something to do with whatever your `com.rme.xopcutil.nodes.NodeDataType.getVariantConstructor` function is doing and how it behaves on JDK 11 vs JDK 17.