springmvc项目中如何使用JSR-303实现对数据进行校验

<!-- 校验错误信息配置文件 -->
 <bean id="messageSource"
  class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
  <!-- 资源文件名-->
  <property name="basenames"> 
   <list> 
   <value>classpath:CustomValidationMessages</value>
   </list> 
  </property>
  <!-- 资源文件编码格式 -->
  <property name="fileEncodings" value="utf-8" />
  <!-- 对资源文件内容缓存时间，单位秒 -->
  <property name="cacheSeconds" value="120" />
 </bean>

<!-- 校验器 -->
 <bean id="validator"
  class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
  <!-- hibernate校验器-->
  <property name="providerClass" value="org.hibernate.validator.HibernateValidator" />
  <!-- 指定校验使用的资源文件，在文件中配置校验错误信息，如果不指定则默认使用classpath下的ValidationMessages.properties -->
  <property name="validationMessageSource" ref="messageSource" />
 </bean>

<mvc:annotation-driven conversion-service="conversionService" validator="validator">
 </mvc:annotation-driven>

import javax.validation.constraints.NotNull; 
public class UserModel { 
 @NotNull(message="{username.not.empty}") 
 private String username; 
} 

@Controller 
public class HelloWorldController { 
 @RequestMapping("/validate/hello") 
 public String validate(@Valid @ModelAttribute("user") UserModel user, Errors errors) { 

  if(errors.hasErrors()) { 
   return "validate/error"; 
  } 
  return "redirect:/success"; 
 } 
} 

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> 
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %> 

<form:form commandName="user"> 
 <form:errors path="*" cssStyle="color:red"></form:errors><br/> 
</form:form> 

public class Items {
 private Integer id;
 @Size(min=1,max=20,message="{items.name.length.error}")
 private String name;

 @NotNull(message="{items.createtime.isNULL}")
 private Date createtime;

 省略set()和get()...
}

public String editItemsSubmit(Model model, @Validated Items items, 
BindingResult bindingResult) throws Exception {
  if(bindingResult.hasErrors()){
   List<ObjectError> allErrors = bindingResult.getAllErrors();
   for(ObjectError objectError:allErrors) {
  System.out.println(objectError.getDefaultMessage());
   }

   //可以直接使用model将提交pojo回显到页面
   model.addAttribute("items",items);

   // 出错重新到商品修改页面
   return "items/editItems";
  }
  return "success";
 }

<table width="100%" border=1>
<tr>
 <td>商品名称</td>
 <td><form:input type="text" path="items.name" value="${items.name }"/></td><form:errors path="items.name"/>
</tr>
<tr>
 <td>商品生产日期</td>
 <td><input type="text" name="createtime" value="<fmt:formatDate value="${items.createtime}" pattern="yyyy-MM-dd HH:mm:ss"/>"/></td>
</tr>