SpringMVC uses @Valid annotation for data validation

When we submit a form, it is not safe to do data validation only on the front end, so sometimes we need to do data validation on the back end as well. Fortunately, SpringMVC provides us with a better support for verification in the background. That is to use the implementation class of the Valid interface for data validation. Before that, let's do some preparatory work.

Add relevant Maven dependencies

Let's add the required jar package first.

		<dependency>
			<groupId>javax.validation</groupId>
			<artifactId>validation-api</artifactId>
			<version>1.1.0.Final</version>
		</dependency>
		<dependency>
			<groupId>org.apache.bval</groupId>
			<artifactId>bval-jsr303</artifactId>
			<version>0.5</version>
		</dependency>

Implement the Validator interface

The next first step we need to write a class to implement the Validator interface. In this class, we need to define a JavaBean that supports validation, and implement the validate method for related validation. The specific implementation classes are as follows:

package com.zkn.learnspringmvc.validtor;

import com.zkn.learnspringmvc.scope.PersonScope;
import org.springframework.util.StringUtils;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

/**
 * Created by wb-zhangkenan on 2016/9/2.
 */
public class PersonalValidtor implements Validator{

    /**
     * Determine supported JavaBean types
     * @param aClass
     * @return
     */
    @Override
    public boolean supports(Class<?> aClass) {
        return PersonScope.class.equals(aClass);
    }

    /**
     * Implement the validate interface in Validator
     * @param obj
     * @param errors
     */
    @Override
    public void validate(Object obj, Errors errors) {
        //Register the verification information to the implementation class of Error
        ValidationUtils.rejectIfEmpty(errors,"name",null,"Name cannot be empty!");
        PersonScope personScope = (PersonScope) obj;
        if(StringUtils.isEmpty(personScope.getAddress())){
            errors.rejectValue("address",null,"Home address cannot be empty!!!!");
        }
    }
}

使用Validtor的校验实现类

我们需要在Controller的类里使用刚才写的Validtor的校验实现类来进行表单数据的校验。我们需要在Controller里用@InitBinder注解把刚才的校验类绑定到WebDataBinder类里。写法如下：

    //绑定PersonalValidator
    @InitBinder
    public void initBinder(WebDataBinder webDataBinder){
        webDataBinder.addValidators(new PersonalValidtor());
    }

接下来我们需要在@RequestMapping这个注解所在的方法上使用@Valid注解进行数据的校验。

    @RequestMapping(value = "testPersonalValidtor.do")
    @ResponseBody
    //直接返回对象
    public Object testPersonalValidtor(@Valid PersonScope personScope, BindingResult bindingResult){
        if(bindingResult.hasErrors()){
            StringBuffer sb = new StringBuffer();
            for(ObjectError objectError : bindingResult.getAllErrors()){
                sb.append(((FieldError)objectError).getField() +" : ").append(objectError.getDefaultMessage());
            }
            return sb.toString();
        }else{
            return personScope;
        }
    }

接下来我们来看一下效果：

请求：http://localhost:8081/testPersonalValidtor.do

结果：

请求：http://localhost:8081/testPersonalValidtor.do?name=张三&address=三元桥

结果：

具体Controller类代码如下：

package com.zkn.learnspringmvc.news.controller;

import com.alibaba.fastjson.JSON;
import com.zkn.learnspringmvc.scope.PersonScope;
import com.zkn.learnspringmvc.validtor.PersonalValidtor;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletResponse;
import javax.validation.Valid;

/**
 * 用来测试PersonalValidator的控制器
 * Created by wb-zhangkenan on 2016/9/2.
 */
@Controller
public class TestPersonlalValidtorController {

    //绑定PersonalValidator
    @InitBinder
    public void initBinder(WebDataBinder webDataBinder){
        webDataBinder.addValidators(new PersonalValidtor());
    }

    @RequestMapping(value = "testPersonalValidtor.do")
    @ResponseBody
    //直接返回对象
    public Object testPersonalValidtor(@Valid PersonScope personScope, BindingResult bindingResult){
        if(bindingResult.hasErrors()){
            StringBuffer sb = new StringBuffer();
            for(ObjectError objectError : bindingResult.getAllErrors()){
                sb.append(((FieldError)objectError).getField() +" : ").append(objectError.getDefaultMessage());
            }
            return sb.toString();
        }else{
            return personScope;
        }
    }
}

PersonScope实体类：

package com.zkn.learnspringmvc.scope;

import java.io.Serializable;

/**
 * Person对象
 * @author zkn
 *
 */

public class PersonScope implements Serializable{

	/**
	 * 序列
	 */
	private static final long serialVersionUID = 1L;
	/**
	 * 姓名
	 */
	private String name;
	/**
	 * 年龄
	 */
	private Integer age;
	/**
	 * 家庭地址
	 */
	private String address;

	private StudentScope studentScope;

	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public Integer getAge() {
		return age;
	}
	
	public void setAge(Integer age) {
		this.age = age;
	}

	@Override
	public String toString() {
		return "PersonDomain [name=" + name + ", age=" + age + "]";
	}

	public StudentScope getStudentScope() {
		return studentScope;
	}

	public void setStudentScope(StudentScope studentScope) {
		this.studentScope = studentScope;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}
}

这里需要注意的是：@Valid要紧挨着JavaBean（即PersonScope），要不然不会生效的。

另外需要注意的是：这里的校验是哪个请求需要校验，就写在哪个请求上。如果需要配置全局的校验的话，可以在 <mvc:annotation-driven/>中配置validator。写法如下：

 <mvc:annotation-driven validator="personalValidtor">

  <bean id="personalValidtor" class="com.zkn.learnspringmvc.validtor.PersonalValidtor"/>

使用<form:errors />标签

上面的错误信息的展示是我们自己来展示的错误信息，但是SpringMVC还给我们提供了一个<form:errors />标签来展示错误信息。例子如下：

    @RequestMapping(value = "testPersonalValidtor02.do")
    public Object testPersonalValidtor01(@Valid PersonScope personScope, BindingResult bindingResult){
        if(bindingResult.hasErrors()){
            return "error";
        }else{
            return "home";
        }
    }

jsp页面内容如下：

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

<form:errors path="personScope.name"/>

注意：<form:errors />标签是SpringMVC提供的，所以我们得引入这个标签库。<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>

效果如下：