java.lang.ClassNotFoundException is raised when referring to the flyway.callbacks property

Which version and edition of Flyway are you using?

6.4.2 CE

Which client are you using? (Command-line, Java API, Maven plugin, Gradle plugin)

Gradle plugin

Which database are you using (type & version)?

Postgres 12

Which operating system are you using?

mac OS Catalina 10.15.2

What did you do?

(Please include the content causing the issue, any relevant configuration settings, the SQL statement that failed (if relevant) and the command you ran.)

1. clone repository
2. run docker-compose up -d
3. run ./gradlew flywayMigrate

I’m using Intellij IDEA 2019.3.3 for development. I wanted to create tables in SQL and populate them with test data in Java. This is because we wanted to change the test data by environment variables.

What did you expect to see?

The ability to perform Java callbacks and submit test data.

What did you see instead?

It’s a stacktrace(./gradlew flywayMigrate --stacktrace).

[mahaker@mahaker-mbp] flyway-callback-java[master]$: ./gradlew flywayMigrate --stacktrace
> Task :flywayMigrate FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':flywayMigrate'.
> Error occurred while executing flywayMigrate
  Unable to instantiate class db.migration.FillTestData : db.migration.FillTestData
  db.migration.FillTestData

* Try:
Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':flywayMigrate'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$2.accept(ExecuteActionsTaskExecuter.java:121)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$2.accept(ExecuteActionsTaskExecuter.java:117)
        at org.gradle.internal.Try$Failure.ifSuccessfulOrElse(Try.java:184)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:110)
        at org.gradle.api.internal.tasks.execution.ResolveIncrementalChangesTaskExecuter.execute(ResolveIncrementalChangesTaskExecuter.java:84)
        at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:91)
        at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionStateTaskExecuter.execute(ResolveBeforeExecutionStateTaskExecuter.java:74)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:109)
        at org.gradle.api.internal.tasks.execution.ResolveBeforeExecutionOutputsTaskExecuter.execute(ResolveBeforeExecutionOutputsTaskExecuter.java:67)
        at org.gradle.api.internal.tasks.execution.ResolveAfterPreviousExecutionStateTaskExecuter.execute(ResolveAfterPreviousExecutionStateTaskExecuter.java:46)
        at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:93)
        at org.gradle.api.internal.tasks.execution.FinalizePropertiesTaskExecuter.execute(FinalizePropertiesTaskExecuter.java:45)
        at org.gradle.api.internal.tasks.execution.ResolveTaskExecutionModeExecuter.execute(ResolveTaskExecutionModeExecuter.java:94)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:57)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:56)
        at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:36)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.executeTask(EventFiringTaskExecuter.java:63)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:49)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.call(EventFiringTaskExecuter.java:46)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:416)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:406)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.call(DefaultBuildOperationExecutor.java:102)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.call(DelegatingBuildOperationExecutor.java:36)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:46)
        at org.gradle.execution.plan.LocalTaskNodeExecutor.execute(LocalTaskNodeExecutor.java:43)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:355)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$InvokeNodeExecutorsAction.execute(DefaultTaskExecutionGraph.java:343)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:336)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareExecutionAction.execute(DefaultTaskExecutionGraph.java:322)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:134)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker$1.execute(DefaultPlanExecutor.java:129)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:202)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:193)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:129)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: org.flywaydb.core.api.FlywayException: Error occurred while executing flywayMigrate
Unable to instantiate class db.migration.FillTestData : db.migration.FillTestData
db.migration.FillTestData
        at org.flywaydb.gradle.task.AbstractFlywayTask.runTask(AbstractFlywayTask.java:550)
        at jdk.internal.reflect.GeneratedMethodAccessor373.invoke(Unknown Source)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:103)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.doExecute(StandardTaskAction.java:48)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:41)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:28)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:705)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:672)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$4.run(ExecuteActionsTaskExecuter.java:338)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:402)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:394)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutor.java:165)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:250)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:158)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:92)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:327)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:312)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.access$200(ExecuteActionsTaskExecuter.java:75)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$TaskExecution.execute(ExecuteActionsTaskExecuter.java:158)
        at org.gradle.internal.execution.impl.steps.ExecuteStep.execute(ExecuteStep.java:46)
        at org.gradle.internal.execution.impl.steps.CancelExecutionStep.execute(CancelExecutionStep.java:34)
        at org.gradle.internal.execution.impl.steps.TimeoutStep.executeWithoutTimeout(TimeoutStep.java:69)
        at org.gradle.internal.execution.impl.steps.TimeoutStep.execute(TimeoutStep.java:49)
        at org.gradle.internal.execution.impl.steps.CatchExceptionStep.execute(CatchExceptionStep.java:34)
        at org.gradle.internal.execution.impl.steps.CreateOutputsStep.execute(CreateOutputsStep.java:49)
        at org.gradle.internal.execution.impl.steps.SnapshotOutputStep.execute(SnapshotOutputStep.java:42)
        at org.gradle.internal.execution.impl.steps.SnapshotOutputStep.execute(SnapshotOutputStep.java:28)
        at org.gradle.internal.execution.impl.steps.CacheStep.executeWithoutCache(CacheStep.java:133)
        at org.gradle.internal.execution.impl.steps.CacheStep.lambda$execute$5(CacheStep.java:83)
        at org.gradle.internal.execution.impl.steps.CacheStep.execute(CacheStep.java:82)
        at org.gradle.internal.execution.impl.steps.CacheStep.execute(CacheStep.java:37)
        at org.gradle.internal.execution.impl.steps.PrepareCachingStep.execute(PrepareCachingStep.java:33)
        at org.gradle.internal.execution.impl.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:38)
        at org.gradle.internal.execution.impl.steps.StoreSnapshotsStep.execute(StoreSnapshotsStep.java:23)
        at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.executeBecause(SkipUpToDateStep.java:95)
        at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.lambda$execute$0(SkipUpToDateStep.java:88)
        at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:52)
        at org.gradle.internal.execution.impl.steps.SkipUpToDateStep.execute(SkipUpToDateStep.java:36)
        at org.gradle.internal.execution.impl.DefaultWorkExecutor.execute(DefaultWorkExecutor.java:34)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:109)
        ... 37 more
Caused by: org.flywaydb.core.api.FlywayException: Unable to instantiate class db.migration.FillTestData : db.migration.FillTestData
        at org.flywaydb.core.internal.util.ClassUtils.instantiate(ClassUtils.java:59)
        at org.flywaydb.core.api.configuration.ClassicConfiguration.setCallbacksAsClassNames(ClassicConfiguration.java:1457)
        at org.flywaydb.core.api.configuration.ClassicConfiguration.configure(ClassicConfiguration.java:1842)
        at org.flywaydb.core.api.configuration.FluentConfiguration.configuration(FluentConfiguration.java:1054)
        at org.flywaydb.gradle.task.AbstractFlywayTask.runTask(AbstractFlywayTask.java:545)
        ... 78 more
Caused by: java.lang.ClassNotFoundException: db.migration.FillTestData
        at org.flywaydb.core.internal.util.ClassUtils.instantiate(ClassUtils.java:57)
        ... 82 more


* Get more help at https://help.gradle.org

BUILD FAILED in 0s
1 actionable task: 1 executed

[Lyeeedar]

Okay so on further investigation, this is actually simpler than we thought. The issue is occurring because the callback class has not yet been built. You can fix this in one of 2 ways.

Solution 1: Make the migrate task depend on the classes task. You can do this by adding flywayMigrate.dependsOn classes to the end of the build.gradle file. Note: If you do this, and you want to run clean or repair or any of the other tasks, you need to add flyway{TaskName}.dependsOn classes for each task.

Solution 2: Call gradle like so: ./gradlew classes flywayMigrate

[Lyeeedar]

We’ve managed to reproduce the issue, and are looking at developing a fix. Hopefully for the next patch.