trouble with custom constraint

package ui.constraints;

import java.math.BigDecimal;

import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.WrongValueException;
import org.zkoss.zul.SimpleConstraint;

@SuppressWarnings("serial")
public class BidConstraint extends SimpleConstraint {

	private float minValue;
	
	public BidConstraint(int flags, float pMinValue) {
		super(flags);
		this.minValue=pMinValue;
	}

	@Override
	public void validate(Component comp, Object value)
			throws WrongValueException {
		super.validate(comp, value); 
		float enteredValue = ((BigDecimal)value).floatValue();
		if (enteredValue<minValue) 
			throw new WrongValueException(comp,"Mindestens "+minValue+"!");	
	}

}

<?xml version="1.0" encoding="UTF-8"?>
<?taglib uri="http://www.zkoss.org/dsp/web/core" prefix="c"?>
<p:zk
xmlns:p="http://www.zkoss.org/2005/zul" 
xmlns:a="http://www.zkoss.org/2005/zk/annotation">
  <?variable-resolver class="org.zkoss.zkplus.jndi.JndiVariableResolver" ?>
  <p:window id="bid" 
  			title="Test Constraints" 
  			border="normal" 
  			width="300px" 
  			sizable="true"
  		 	closable="true">

		<p:zscript>
		   <![CDATA[
				import java.math.BigDecimal;
				
				import org.zkoss.zk.ui.Component;
				import org.zkoss.zk.ui.WrongValueException;
				import org.zkoss.zul.SimpleConstraint;
				import ui.constraints.BidConstraint;
				
				BidConstraint myBidConstraint 
							        = new BidConstraint(
							        		org.zkoss.zul.SimpleConstraint.NO_EMPTY
							        	   |org.zkoss.zul.SimpleConstraint.NO_NEGATIVE
							        	   ,(float)1000);
	        ]]>
		</p:zscript>

        <p:grid>
        <p:rows>
	        <p:row>
	        	<p:decimalbox constraint="${myBidConstraint}"/>
	        </p:row>
	        <p:row>
	        	<p:decimalbox constraint="no empty, no negative"/>
	        </p:row>
   		</p:rows>
   		</p:grid>
   </p:window>
</p:zk>

package ui;

import org.zkoss.zk.ui.Page;
import org.zkoss.zkplus.databind.AnnotateDataBinderInit;
import org.zkoss.zul.SimpleConstraint;
import ui.constraints.BidConstraint;


public class Test4WindowInit extends AnnotateDataBinderInit {

	private BidConstraint myBidConstraint;
	
	@Override
	public void doAfterCompose(Page page) {
	        myBidConstraint 
	        = new BidConstraint(SimpleConstraint.NO_EMPTY
	        					|SimpleConstraint.NO_NEGATIVE
	        					,1000);
	        
	        page.setVariable("myBidConstraint", myBidConstraint); 
	        super.doAfterCompose(page); 
	    }
	
}