SpringMVC Validation验证（帖子最后有个问题，麻烦大神指点一下）

package com.domain;

import java.io.Serializable;

public class User implements Serializable {
    private String loginname;
    private String password;
    public String getLoginname() {
        return loginname;
    }
    public void setLoginname(String loginname) {
        this.loginname = loginname;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

package com.validator;

import org.springframework.stereotype.Repository;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

import com.domain.User;

@Repository("userValidator")//注解将该对象注释为Spring容器中的一个bean，名字为userValidator
public class UserValidator implements Validator {

    /**该校验器能够对clazz类型的对象进行校验*/
    @Override
    public boolean supports(Class<?> clazz) {
        // TODO Auto-generated method stub
        return User.class.isAssignableFrom(clazz);
    }

    /**对目标target进行校验，并将校验错误存到errors中*/
    @Override
    public void validate(Object target, Errors errors) {
        // TODO Auto-generated method stub
        ValidationUtils.rejectIfEmpty(errors, "loginname", "loginnameError");
        ValidationUtils.rejectIfEmpty(errors, "password", "passwordError");
        User user = (User)target;
        if(user.getLoginname().length() > 10)
        {
            errors.rejectValue("loginname", null, "loginnameMax");
        }

        if(user.getPassword() != null && user.getPassword().length() < 6)
        {
            errors.rejectValue("password", null, "passwordMin");
        }
    }

}

package com.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.Errors;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.domain.User;
import com.validator.UserValidator;

@Controller
public class UserController{

    //注入userValidator
    @Autowired
    @Qualifier("userValidator")
    private UserValidator userValidator;

    @RequestMapping(value="/login",method=RequestMethod.POST)
    public String login(@ModelAttribute User user,Model model,Errors errors)
    {
        model.addAttribute("user", user);
        //验证
        userValidator.validate(user, errors);
        if(errors.hasErrors())
        {
            return "loginForm";
        }
        return "success";
    }

    @RequestMapping(value="/{formName}")
    public String loginForm(@PathVariable String formName,Model model)
    {
        User user = new User();
        model.addAttribute("user", user);
        return formName;//动态页面的跳转，可以是任何页面
    }

}

 <context:component-scan base-package="com.controller"></context:component-scan>
        <context:component-scan base-package="com.validator"></context:component-scan>
       <mvc:annotation-driven></mvc:annotation-driven>
        <!-- 配置视图解析器 如何把handler 方法返回值解析为实际的物理视图 -->
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix">
                <value>/WEB-INF/content/</value>
            </property>
            <property name="suffix">
                <value>.jsp</value>
            </property>
        </bean>

        <!-- 国际化 -->
        <bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
            <property name="basenames">
                <list>
                    <!-- 在web环境中一定要定位到classpath，放在src目录下-->
                    <value>classpath:messages</value>
                </list>
            </property>
            <property name="useCodeAsDefaultMessage" value="false"/>
            <property name="defaultEncoding" value="UTF-8"/>
            <property name="cacheSeconds" value="60"/>
        </bean>
        <mvc:interceptors >
            <bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"></bean>
        </mvc:interceptors>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>测试Validation接口验证</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>

  <body>
    <h3>登录页面</h3>
    <form:form modelAttribute="user" method="post" action="login">
        <table>
            <tr>
                <td>登录名</td>
                <td><form:input path="loginname"/></td>
                <!-- 显示错误信息 -->
                <td><form:errors path="loginname" cssStyle="Color:red"></form:errors></td>
            </tr>
            <tr>
                <td>密码</td>
                <td><form:input path="password"/></td>
                <td><form:errors path="password" cssStyle="Color:red"></form:errors></td>
            </tr>
            <tr>
                <td><input type="submit" value="提交"/></td>
            </tr>
        </table>
    </form:form>
  </body>
</html>