java.lang.ClassNotFoundException: javassist.ClassPool Exception Handling

problem:

十一月 05, 2019 3:38:20 下午 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter struts2
java.lang.reflect.InvocationTargetException - Class: com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector
File: ContainerImpl.java
Method: inject
Line: 301 - com/opensymphony/xwork2/inject/ContainerImpl.java:301:-1
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:504)
    at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
    at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4908)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5602)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1572)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1562)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector.inject(ContainerImpl.java:301)
    at com.opensymphony.xwork2.inject.ContainerImpl$ConstructorInjector.construct(ContainerImpl.java:438)
    at com.opensymphony.xwork2.inject.ContainerBuilder$5.create(ContainerBuilder.java:207)
    at com.opensymphony.xwork2.inject.Scope$2$1.create(Scope.java:51)
    at com.opensymphony.xwork2.inject.ContainerBuilder$3.create(ContainerBuilder.java:93)
    at com.opensymphony.xwork2.inject.ContainerBuilder$7.call(ContainerBuilder.java:487)
    at com.opensymphony.xwork2.inject.ContainerBuilder$7.call(ContainerBuilder.java:484)
    at com.opensymphony.xwork2.inject.ContainerImpl.callInContext(ContainerImpl.java:584)
    at com.opensymphony.xwork2.inject.ContainerBuilder.create(ContainerBuilder.java:484)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.createBootstrapContainer(DefaultConfiguration.java:351)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:235)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
    at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:978)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:446)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:490)
    ... 14 more
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector.inject(ContainerImpl.java:299)
    ... 28 more
Caused by: java.lang.ExceptionInInitializerError
    at com.opensymphony.xwork2.ognl.OgnlValueStackFactory.setContainer(OgnlValueStackFactory.java:84)
    ... 33 more
Caused by: java.lang.IllegalArgumentException: Javassist library is missing in classpath! Please add missed dependency!
    at ognl.OgnlRuntime.<clinit>(OgnlRuntime.java:169)
    ... 34 more
Caused by: java.lang.ClassNotFoundException: javassist.ClassPool
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1858)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1701)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:190)
    at ognl.OgnlRuntime.<clinit>(OgnlRuntime.java:166)
    ... 34 more

Solution:

　　javassist-3.20.0-GA.jar package to