波总：

创建一个普通的maven工程，其中某个类为 com.jfinal.handler.Handler的子类，如图

使用 jfinal_demo_for_maven工程，引入外部jar包

使用如下

启动报错：

Starting JFinal 4.8 -> http://0.0.0.0:80
Info: jfinal-undertow 2.0, undertow 2.0.28.Final, jvm 1.8.0_131
Exception in thread "main" java.lang.VerifyError: Bad type on operand stack
Exception Details:
  Location:
    com/demo/common/DemoConfig.configHandler(Lcom/jfinal/config/Handlers;)V @8: invokevirtual
  Reason:
    Type 'com/sl/jfinal/swagger/handler/SwaggerValidatorHandler' (current frame, stack[1]) is not assignable to 'com/jfinal/handler/Handler'
  Current Frame:
    bci: @8
    flags: { }
    locals: { 'com/demo/common/DemoConfig', 'com/jfinal/config/Handlers' }
    stack: { 'com/jfinal/config/Handlers', 'com/sl/jfinal/swagger/handler/SwaggerValidatorHandler' }
  Bytecode:
    0x0000000: 2bbb 0026 59b7 0027 b600 2857 b1       

	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.jfinal.core.JFinalFilter.createJFinalConfig(JFinalFilter.java:126)
	at com.jfinal.core.JFinalFilter.init(JFinalFilter.java:61)
	at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:111)
	at io.undertow.servlet.core.ManagedFilter.createFilter(ManagedFilter.java:80)
	at io.undertow.servlet.core.DeploymentManagerImpl$2.call(DeploymentManagerImpl.java:591)
	at io.undertow.servlet.core.DeploymentManagerImpl$2.call(DeploymentManagerImpl.java:556)
	at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:42)
	at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
	at io.undertow.servlet.core.DeploymentManagerImpl.start(DeploymentManagerImpl.java:598)
	at com.jfinal.server.undertow.UndertowServer.configHttp(UndertowServer.java:284)
	at com.jfinal.server.undertow.UndertowServer.doStart(UndertowServer.java:262)
	at com.jfinal.server.undertow.UndertowServer.start(UndertowServer.java:159)
	at com.jfinal.server.undertow.UndertowServer.start(UndertowServer.java:84)
	at com.demo.common.DemoConfig.main(DemoConfig.java:34)

Process finished with exit code 1

如果这么使用，又是正常的

请问是怎么回事？