Spring MVC框架errors标签的使用

今天药忘吃喽~ 2022-10-01 00:39 122阅读 0赞

代码：

registerForm.jsp

<%@ 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>

User.java

package com.bean;
    
    import java.io.Serializable;
    
    public class User implements Serializable {
    	private String username;
    	private String sex;
    	private Integer age;
    	public User() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	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;
    	}
    	
    }

UserValidator.java

package com.validator;
    
    import org.springframework.validation.Errors;
    import org.springframework.validation.ValidationUtils;
    import org.springframework.validation.Validator;
    
    import com.bean.User;
    
    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"); 
    	}
    }

UserController.java

package com.control;
    
    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.InitBinder;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    import com.bean.User;
    import com.validator.UserValidator;
    
    @Controller
    public class UserController {
    	@RequestMapping(value="/registerForm",method=RequestMethod.GET)
    	 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());
    	}
    	
    	@RequestMapping(value="/register",method=RequestMethod.POST)
    	 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"; 
    	}
    }

截图：

![Center][]

![Center 1][]

[Center]: /images/20220705/3c11b97a5dfa4725be83e95529f92665.png
[Center 1]: /images/20220705/028f856a1c2a448db33bef5f28abea28.png