Thread: can't start jnlp file

hi all :
when i start my jnlp ,it's shown the error msg as follows :

MissingFieldException[ Start a file to be in need of the following and necessary column ： <jnlp>(<application-desc>|<applet-desc>|<installer-desc>|<component-desc>)]
	at com.sun.javaws.jnl.XMLFormat.parse(Unknown Source)
	at com.sun.javaws.jnl.LaunchDescFactory.buildDescriptor(Unknown Source)
	at com.sun.javaws.jnl.LaunchDescFactory.buildDescriptor(Unknown Source)
	at com.sun.javaws.Launcher.updateFinalLaunchDesc(Unknown Source)
	at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
	at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
	at com.sun.javaws.Launcher.launch(Unknown Source)
	at com.sun.javaws.Main.launchApp(Unknown Source)
	at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
	at com.sun.javaws.Main$1.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

i have add application-des to my jnlp file ,but why still have the error ??

What does the contents of this file look like?

// Json