Flyway Java回调

我有一个maven flyway项目,其中只包含要运行的sql脚本。以下是此项目的目录结构:

src/
├── main/
    └── java/
        └── callbacks/
            ├── FooCallback.java
    └── resources/
        └── db/
            ├── Script1.sql
            ├── Script2.sql
            ├── Script3.sql
            └── ...

以下是我的 pom.xml :

<properties>
    <java.version>1.8</java.version>
    <maven.flyway.version>5.0.6</maven.flyway.version>
    <flyway.callbacks>main.java.callbacks.FooCallbback</flyway.callbacks>
    <flyway.outOfOrder>true</flyway.outOfOrder>
    <url>...</url>
    <user>...</user>
    <password>...</password>
    <locations>db</locations>
</properties>

但每次我跑步 flyway:migrate 我得到以下错误:

[ERROR] Failed to execute goal org.flywaydb:flyway-maven-plugin:4.0.3:migrate (default-cli) on project database: org.flywaydb.core.api.FlywayException: Unable to instantiate class: main.java.callbacks.FooCallback -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.flywaydb:flyway-maven-plugin:4.0.3:migrate (default-cli) on project database: org.flywaydb.core.api.FlywayException: Unable to instantiate class: main.java.callbacks.FooCallback
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
    at org.codehaus.classworlds.Launcher.main(Launcher.java:47)
Caused by: org.apache.maven.plugin.MojoExecutionException: org.flywaydb.core.api.FlywayException: Unable to instantiate class: main.java.callbacks.FooCallback
    at org.flywaydb.maven.AbstractFlywayMojo.execute(AbstractFlywayMojo.java:541)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
    ... 21 more
Caused by: java.lang.ClassNotFoundException: main.java.callbacks.FooCallback
    at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(ClassRealm.java:271)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:247)
    at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:239)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at org.flywaydb.core.internal.util.ClassUtils.instantiate(ClassUtils.java:49)
    at org.flywaydb.core.internal.util.ClassUtils.instantiateAll(ClassUtils.java:65)
    at org.flywaydb.core.Flyway.setCallbacksAsClassNames(Flyway.java:867)
    at org.flywaydb.core.Flyway.configure(Flyway.java:1263)
    at org.flywaydb.maven.AbstractFlywayMojo.execute(AbstractFlywayMojo.java:537)
    ... 23 more

很明显,我的文件夹结构有点混乱。我已尝试将文件夹结构更改为:

src/
├── main/
    └── resources/
        └── db/
            └── callbacks/
                ├── FooCallback.java
            ├── Script1.sql
            ├── Script2.sql
            ├── Script3.sql
            └── ...

以及我的pom属性:

<flyway.callbacks>db.callbacks.FooCallback</flyway.callbacks>

但我还是犯了同样的错误。如何让它运行而不出现问题?