http://screencast.com/t/g2BtyJGNwsI

<zk>
	<zscript><![CDATA[
		class MyVM {
			private Integer number;
			
			private int numberInt;
			
			public void setNumber (Integer number) {
				this.number = number;
			}
			
			public Integer getNumber() {
				return number;
			}
			
			public void setNumberInt (int numberInt) {
				this.numberInt = numberInt;
			}
			
			public int getNumberInt() {
				return numberInt;
			}
		}
			
	]]></zscript>
	
	<window apply="org.zkoss.bind.BindComposer" 
		viewModel="@id('vm') @init('MyVM')">
		
		Integer: <spinner value="@bind(vm.number)"/>
		<separator/>
		int: <spinner value="@bind(vm.numberInt)"/>
		 
	</window>

</zk>

org.zkoss.zk.ui.UiException: Error reading 'value' on type org.zkoss.zul.Spinner at file:/C:/ws/ZK6/testZK65/src/main/webapp/test6.zul, line:32
at org.zkoss.bind.impl.MiscUtil.mergeExceptionInfo(MiscUtil.java:175)
at org.zkoss.bind.impl.BindEvaluatorXImpl.getValue(BindEvaluatorXImpl.java:48)
at org.zkoss.bind.impl.SavePropertyBindingImpl.getComponentValue(SavePropertyBindingImpl.java:105)
at org.zkoss.bind.impl.SavePropertyBindingImpl.save(SavePropertyBindingImpl.java:130)
at org.zkoss.bind.impl.PropertyBindingHandler.doSaveBinding(PropertyBindingHandler.java:148)
at org.zkoss.bind.impl.PropertyBindingHandler.doSaveEvent(PropertyBindingHandler.java:203)
.....etc
Caused by: org.zkoss.zel.ELException: Error reading 'value' on type org.zkoss.zul.Spinner
at org.zkoss.zel.BeanELResolver.getValue(BeanELResolver.java:95)
at org.zkoss.zel.CompositeELResolver.getValue(CompositeELResolver.java:66)
at org.zkoss.zel.CompositeELResolver.getValue(CompositeELResolver.java:66)
at org.zkoss.xel.zel.XelELResolver.getValue(XelELResolver.java:72)
at org.zkoss.bind.xel.zel.BindELResolver.getValue(BindELResolver.java:69)
at org.zkoss.zel.impl.parser.AstValue.getValue(AstValue.java:177)
at org.zkoss.zel.impl.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
at org.zkoss.xel.zel.ELXelExpression.evaluate(ELXelExpression.java:40)
at org.zkoss.bind.impl.BindEvaluatorXImpl.getValue(BindEvaluatorXImpl.java:46)
... 35 more
Caused by: org.zkoss.zk.ui.WrongValueException: You must specify an integer, rather than null.
at org.zkoss.zul.Spinner.getTargetValue(Spinner.java:69)
at org.zkoss.zul.Spinner.getValue(Spinner.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.zkoss.zel.BeanELResolver.getValue(BeanELResolver.java:89)
... 43 more