HTTP Status 500 错误

报错如下：
type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException: Error instantiating servlet class gov.nist.registry.xdstools.servlets.PidAllocateServlet
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.valves.FastCommonAccessLogValve.invoke(FastCommonAccessLogValve.java:482)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:542)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:834)
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:640)
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1286)
java.lang.Thread.run(Thread.java:595)
root cause java.lang.NoClassDefFoundError: gov/nist/registry/common2/exception/XdsInternalException
java.lang.Class.getDeclaredConstructors0(Native Method)
java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
java.lang.Class.getConstructor0(Class.java:2671)
java.lang.Class.newInstance0(Class.java:321)
java.lang.Class.newInstance(Class.java:303)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.valves.FastCommonAccessLogValve.invoke(FastCommonAccessLogValve.java:482)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:542)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:834)
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:640)
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1286)
java.lang.Thread.run(Thread.java:595)注：gov.nist.registry.xdstools.servlets.PidAllocateServlet 这个类是存在的，且路径无误。求助！！