JMX:The MBean class could not be loaded...救命

我调试Jmx的自带例子总是报错,如下:javax.management.ReflectionException: The MBean class could not be loaded by the default loader repository
!!! Could not create the SimpleStandard MBean !!!
at com.sun.jmx.mbeanserver.MBeanInstantiatorImpl.findClassWithDefaultLoaderRepository(MBeanInstantiatorImpl.java:69)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:278)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:218)
at com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:309)
at basic.Server.createSimpleMBean(Server.java:127)
at basic.Server.main(Server.java:56)
Caused by: java.lang.ClassNotFoundException: SimpleStandard
at com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:217)
at com.sun.jmx.mbeanserver.ClassLoaderRepositorySupport.loadClass(ClassLoaderRepositorySupport.java:140)好象是运行时classloader的问题．．．我用的eclipse不知有大哥遇到过类似问题?