model-view-controller - Spring 3 MVC : Show validation message with custom validator

Question

我需要帮助。我是jsp，MVC的初学者。我想在 Spring 3 MVC 中使用自定义验证器验证表单输入。

我的验证器类

   package validators;

import models.UserModel;

import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
@Component
public class UserValidator implements Validator {

   @Override
   public boolean supports(Class clazz) {
      return UserModel.class.isAssignableFrom(clazz);
   }

   @Override
   public void validate(Object target, Errors errors) {
      ValidationUtils.rejectIfEmptyOrWhitespace(errors, "firstname", "Enter firstname.");
      ValidationUtils.rejectIfEmptyOrWhitespace(errors, "surname", "Enter surname.");
      ValidationUtils.rejectIfEmptyOrWhitespace(errors, "login", "Enter login.");

   }

}

Controller 类

package controllers;

import java.util.ArrayList;
import models.UserModel;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import validators.UserValidator;
import database.UserDB;


@Controller
public class UserController {

@RequestMapping(value="pouzivatel/new", method=RequestMethod.POST)
   public ModelAndView newUser(@ModelAttribute UserModel user, BindingResult result){
      UserValidator validator = new UserValidator();
      validator.validate(user, result);
      if(result.hasErrors()){
         return new ModelAndView("/user/new","command",user);

      }
      ...
}

用户模型

package models;

public class UserModel  {
   private String firstname="";
   private String surname="";

   public String getFirstname() {
      return firstname;
   }
   public String getSurname() {
      return surname;
   }

   public void setFirstname(String firstname) {
      this.firstname = firstname;
   }
   public void setSurname(String surname) {
      this.surname = surname;
   }

}

JSP veiw new.jsp 位于目录/web-inf/user 中(它只是形式)

<form:form method="post" action="new.html">
            <fieldset>
               <table>
                  <tr>
                     <td>
                        <form:label path="firstname">FirstName</form:label>
                     </td>
                     <td>
                        <form:input path="firstname" />
                        <form:errors path="firstname" />
                     </td>
                  </tr>
                  <tr>
                     <td>
                        <form:label path="surname">Surname</form:label>
                     </td>
                     <td>
                        <form:input path="surname" />
                        <form:errors path="surname" />
                     </td>
                  </tr>
               </table>
            </fieldset>
            <div>
               <button type="submit" id="btOk">Ok</button>
            </div>
</form:form>

调度程序 servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:p="http://www.springframework.org/schema/p"
   xmlns:context="http://www.springframework.org/schema/context"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context-3.0.xsd">

   <context:component-scan base-package="controllers" />
    <context:component-scan base-package="validators" />

   <bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
      <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
      <property name="prefix" value="/WEB-INF/jsp/" />
      <property name="suffix" value=".jsp" />
   </bean>

</beans>

问题是 View 中的显示验证消息。验证成功并且在变量resut (BindingResult) 中是错误的。 Controller 返回跟随部分代码

if(result.hasErrors()){
         return new ModelAndView("/user/new","command",user);

另一种方法是使用注释验证(我更喜欢自定义验证器)，但是当输入字段为空时，为什么我看不到验证消息。

你能给我举个例子吗？

感谢回复。

Answer 1

这是因为 View 和 Controller 中的默认模型属性名称不匹配:

• 当你写 <form:form>没有 modelAttribute (或 commandName )属性，它使用默认模型属性名称 command .
• 当你写 @ModelAttribute UserModel user在您的 Controller 中，它假定此属性的名称是一个非大写的类名，即 userModel .

也就是说，验证器产生的错误消息绑定(bind)到名为 userModel 的模型属性。 ，而您的 View 试图显示模型属性的错误 command .

您需要在 View (<form:form modelAttribute = "userModel" ...>) 或 Controller (@ModelAttribute("command")) 中显式设置模型属性名称。