<?import foo.*?>
<zk>
	<window border="normal" width="200px" apply="MyComposer"> <!-- works here -->
		<label id="msg" />
		<zscript><![CDATA[
			MyBean myBean = new MyBean(); // but throws exception here
			msg.setValue(myBean.getHello());
		]]></zscript>
	</window>
</zk>

package foo;

public class MyBean {
	public String getHello() {
		return "hello";
	}
}

package foo;

import org.zkoss.zk.ui.select.SelectorComposer;
import org.zkoss.zul.Window;

public class MyComposer extends SelectorComposer<Window> {
	private static final long serialVersionUID = 1L;

	@Override
	public void doAfterCompose(Window win) throws Exception {
		super.doAfterCompose(win);
		win.setTitle("hello");
	}
}

<zk>
	<zscript><![CDATA[
			import foo.*;
	]]></zscript>
	<window border="normal" width="200px" apply="MyComposer">
		<label id="msg" />
		<zscript><![CDATA[
			MyBean myBean = new MyBean(); 
			msg.setValue(myBean.getHello());
		]]></zscript>
	</window>
</zk>