Java Error:

com.hazelcast.nio.serialization.HazelcastSerializationException: Problem while reading Externalizable class: tws.usmc.assignment.Unit, exception: java.io.OptionalDataException

Stack Trace:

1: com.hazelcast.nio.serialization.HazelcastSerializationException: Problem while reading Externalizable class: tws.usmc.assignment.Unit, exception: java.io.OptionalDataException
2: at com.hazelcast.internal.serialization.impl.defaultserializers.JavaDefaultSerializers$ExternalizableSerializer.read(JavaDefaultSerializers.java:167)
3: at com.hazelcast.internal.serialization.impl.defaultserializers.JavaDefaultSerializers$ExternalizableSerializer.read(JavaDefaultSerializers.java:143)
4: at com.hazelcast.internal.serialization.impl.StreamSerializerAdapter.read(StreamSerializerAdapter.java:44)
5: at com.hazelcast.internal.serialization.impl.AbstractSerializationService.toObject(AbstractSerializationService.java:271)
6: at com.hazelcast.map.impl.proxy.MapProxySupport.toObject(MapProxySupport.java:1335)
7: at com.hazelcast.map.impl.proxy.MapProxyImpl.get(MapProxyImpl.java:123)
8: at tws.webapp.cache.HazelcastCache.get(Unknown Source)
9: at tws.usmc.assignment.UnitAbst.read(Unknown Source)
10: at tws.usmc.assignment.UnitAbst.getisFolder(Unknown Source)
11: at tws.usmc.assignment.Unit.getFullName(Unknown Source)
12: at tws.usmc.assignment.Unit.getShowName(Unknown Source)
13: at tws.usmc.assignment.Unit.getShowName(Unknown Source)
14: at tws.usmc.assignment.Unit.getName(Unknown Source)
15: at tws.usmc.assignment.CmdPublicUnit.execute(Unknown Source)
16: at tws.webapp.Command.execute(Unknown Source)
17: at tws.webapp.CmdExecute.doCmd(Unknown Source)
18: at tws.webapp.WebApp.doGet(Unknown Source)
19: at javax.servlet.http.HttpServlet.service(HttpServlet.java:489)
20: at javax.servlet.http.HttpServlet.service(HttpServlet.java:583)
21: at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:212)
22: at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
23: at tws.webapp.api.oauth.OAuth2Filter.doFilter(Unknown Source)
24: at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
25: at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
26: at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
27: at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
28: at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
29: at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:381)
30: at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:181)
31: at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:156)
32: at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167)
33: at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90)
34: at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483)
35: at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130)
36: at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93)
37: at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
38: at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
39: at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:533)
40: at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
41: at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:932)
42: at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1695)
43: at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
44: at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
45: at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
46: at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
47: at java.lang.Thread.run(Thread.java:748)
48: null