Ext.form.ComboBox 交付始终获得displayField的值

var alertLevel = new Ext.form.ComboBox( {
			id:'cmb_alertLevel',
		 	hiddenName:"level",	//提交到后台的input的name 
			store: new Ext.data.SimpleStore({
		        fields: ['myId', 'displayText'],
		        data: [['0', 'Emergency'], ['1','Alert'],
		        			['2','Critical'],['3','Error'],
		        			['4','Warning'],['5','Notice'],
		        			['6','Informational'],['7','Debug']]
            }),
    		valueField: 'myId',	//option.value
    		displayField: 'displayText', //option.text
			typeAhead : true,
			triggerAction : 'all',
			emptyText : '所有',
			mode: 'local',
			applyTo : 'alertLevel'
		});		

?

重要属性设置 hiddenName:'level'。??后台直接通过 String alertLevel = request.getParameter("level");获取值