Virtual machine console does not work with web interface of Oracle VM manager

Symptom ==========
The tightVNC package has been installed correctly. But connect to guest console via Oracle VM manager, failed with following error messages:
java.lang.ClassNotFoundException: VncViewer.class
    at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: open HTTP connection failed:https://10.182.113.145:4443/OVS/faces/app/VncViewer/class.class