SerializationException,I don't know why ,Help me.Thanks

[jvincent]

in my project ,there is a class named com.xzuf.client.vo.UfRoleDTO,and
it is exist!but , when i create a UfRoleDTO object and put it into
datebase, it caught a exception :
com.google.gwt.user.client.rpc.SerializationException:
java.lang.ClassNotFoundException: com.xzuf.client.vo.UfRoleDTO
at
com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserialize(ServerSerializationStreamReader.java:150)
at
com.google.gwt.user.client.rpc.impl.AbstractSerializationStreamReader.readObject(AbstractSerializationStreamReader.java:59)
at
com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader.deserializeValue(ServerSerializationStreamReader.java:62)
at
com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:251)
at
com.google.gwt.user.server.rpc.RemoteServiceServlet.doPost(RemoteServiceServlet.java:146)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:270)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:191)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:227)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:211)
at
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:817)
at
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:623)
at
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:444)
at java.lang.Thread.run(Thread.java:595)