STRUTS问题- form bean的validate方法为什么没能给我返回error？
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功能：输入USERNAM将会有欢迎字样；
? 输入错误（NULL）将会有ERROR提示；
? 输入正确时限是正确
?
? error显示页：
? <%@ page contentType="text/html;charset=UTF-8" language="java" %>
? <%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
? <%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
? <%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
?
? <html:html locale="true">
? <head>
? <title><bean:message key="hello.jsp.title"/></title>
? <html:base/>
? </head>
?
? <body bgcolor="white"><p>
? <h2><bean:message key="hello.jsp.page.heading"/></h2><p>
? <html:errors /><p>
?
? <logic:present name="personbean" scope="request">
? <h2>
? <bean:message key="hello.jsp.page.hello"/>
? <bean:write name="personbean" property="userName" />!<p>
? </h2>
? </logic:present>
?
? <html:form action="/HelloWorld.do" focus="userName" >
? <bean:message key="hello.jsp.prompt.person"/>
? <html:text property="userName" size="16" maxlength="16"/><br>
? <html:submit property="submit" value="Submit"/>
? <html:reset/>
?
? </html:form><br>
?
? <html:img page="/img/cat.jpg" alt="STRUTS有关问题- form bean的validate方法为什么没能给小弟我返回error"/>
? </body>
? </html:html>
?
? formbean:
? package hello;
?
? import javax.servlet.http.HttpServletRequest;
? import org.apache.struts.action.ActionMessage;
? import org.apache.struts.action.ActionErrors;
? import org.apache.struts.action.ActionForm;
? import org.apache.struts.action.ActionMapping;
?
? public final class HelloForm extends ActionForm {
?
? private String userName = null;
?
? public String getUserName() {
? return (this.userName);
? }
?
? public void setUserName(String userName) {
? this.userName = userName;
? }
?
? /**
? * Reset all properties to their default values.
? */
? public void reset(ActionMapping mapping, HttpServletRequest request) {
? this.userName = null;
? }
?
? /**
? * Validate the properties posted in this request. If validation errors are
