Spring MVC的errors标签的使用

旧城等待， 2021-07-24 18:24 354阅读 0赞

**一 领域模型**

package org.fkit.domain;
    import java.io.Serializable;
    
    // 域对象，实现序列化接口
    public class User implements Serializable{
         
         private static final long serialVersionUID = 1L;
         
         private String username;
         private String sex;
         private Integer age;
         
         public User() {
               super();
         }
         public String getUsername() {
               return username;
         }
         public void setUsername(String username) {
               this.username = username;
         }
         public String getSex() {
               return sex;
         }
         public void setSex(String sex) {
               this.sex = sex;
         }
         public Integer getAge() {
               return age;
         }
         public void setAge(Integer age) {
               this.age = age;
         }
         
    }

**二 控制器**

package org.fkit.controller;
    
    
    import org.fkit.domain.User;
    import org.fkit.validator.UserValidator;
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.validation.DataBinder;
    import org.springframework.validation.Errors;
    import org.springframework.validation.annotation.Validated;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.InitBinder;
    import org.springframework.web.bind.annotation.PostMapping;
    
    
    /**
    *  HelloWorldController是一个基于注解的控制器,
    *  可以同时处理多个请求动作，并且无须实现任何接口。
    *  org.springframework.stereotype.Controller注解用于指示该类是一个控制器
    */
    @Controller
    public class UserController{
         
         @GetMapping(value="/registerForm")
         public String registerForm(Model model) {
             User user = new User();
             // model中添加属性user，值是user对象
             model.addAttribute("user",user);
             return "registerForm";
         }
         
         @InitBinder  
         public void initBinder(DataBinder binder) {  
            // 设置验证的类为UserValidator
            binder.setValidator(new UserValidator());  
         }
         
         @PostMapping(value="/register")
         public String register(@Validated User user, Errors errors) {
             // 如果Errors对象有Field错误的时候，重新跳回注册页面，否则正常提交
             if (errors.hasFieldErrors())  
                 return "registerForm";  
             return "submit";
         }
    }

**三 验证器**

package org.fkit.validator;
    
    import org.fkit.domain.User;
    import org.springframework.validation.Errors;
    import org.springframework.validation.ValidationUtils;
    import org.springframework.validation.Validator;
    
    public class UserValidator implements Validator{
    
        @Override
        public boolean supports(Class<?> clazz) {
            return User.class.equals(clazz);
        }
    
        @Override
        public void validate(Object object, Errors errors) {
            // 验证username、sex和age是否为null
            ValidationUtils.rejectIfEmpty(errors, "username", null, "用户名不能为空");  
            ValidationUtils.rejectIfEmpty(errors, "sex", null, "性别不能为空");
            ValidationUtils.rejectIfEmpty(errors, "age", null, "年龄不能为空");
        }
    
    }

**四 视图**

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <%@ taglib prefix="form"  uri="http://www.springframework.org/tags/form" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"  "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html;  charset=UTF-8">
    <title>测试errors标签</title>
    </head>
    <body>
    <h3>注册页面</h3>
    <form:form modelAttribute="user" method="post" action="register"  >
         <table>
               
               <tr>
                    <td>姓名:</td>
                    <td><form:input path="username"/></td>
                    <td><font color="red"><form:errors  path="username"/></font></td>
               </tr>
               <tr>
                    <td>性别:</td>
                    <td><form:input path="sex"/></td>
                    <td><font color="red"><form:errors  path="sex"/></font></td>
               </tr>
               <tr>
                    <td>年龄:</td>
                    <td><form:input path="age"/></td>
                    <td><font color="red"><form:errors  path="age"/></font></td>
               </tr>
               <tr>  
                <td><input type="submit" value="注册"/></td>  
            </tr>  
         </table>
    </form:form>
    </body>
    </html>

**五 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

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