Spring Validation概述

在开发中，我们经常遇到参数校验的需求，比如用户注册的时候，要校验用户名不能为空、用户名长度不超过20个字符、手机号是合法的手机号格式等等。如果使用普通方式，我们会把校验的代码和真正的业务处理逻辑耦合在一起，而且如果未来要新增一种校验逻辑也需要在修改多个地方。而spring validation允许通过注解的方式来定义对象校验规则，把校验和业务逻辑分离开，让代码编写更加方便。Spring Validation其实就是对Hibernate Validator进一步的封装，方便在Spring中使用。

在Spring中有多种校验的方式

第一种是通过实现org.springframework.validation.Validator接口，然后在代码中调用这个类

第二种是按照Bean Validation方式来进行校验，即通过注解的方式。

第三种是基于方法实现校验

除此之外，还可以实现自定义校验

实验一：通过Validator接口实现

1.引入相关依赖

<dependencies><dependency><groupId>org.hibernate.validator</groupId><artifactId>hibernate-validator</artifactId><version>7.0.5.Final</version></dependency><dependency><groupId>org.glassfish</groupId><artifactId>jakarta.el</artifactId><version>4.0.1</version></dependency>
</dependencies>

2.创建实体类，定义属性和方法

public class Person {private String name;private int age;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

3.创建类实现Validator接口，实现接口方法指定校验规则

import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;public class PersonValidator implements Validator {@Overridepublic boolean supports(Class<?> clazz) {return Person.class.equals(clazz);}@Overridepublic void validate(Object object, Errors errors) {ValidationUtils.rejectIfEmpty(errors, "name", "name.empty");Person p = (Person) object;if (p.getAge() < 0) {errors.rejectValue("age", "error value < 0");} else if (p.getAge() > 110) {errors.rejectValue("age", "error value too old");}}
}

上面定义的类，其实就是实现接口中对应的方法，

supports方法用来表示此校验用在哪个类型上，

validate是设置校验逻辑的地点，其中ValidationUtils，是Spring封装的校验工具类，帮助快速实现校验。

4.使用上述Validator进行测试

import org.springframework.validation.BindingResult;
import org.springframework.validation.DataBinder;public class TestMethod1 {public static void main(String[] args) {//创建person对象Person person = new Person();person.setName("lucy");person.setAge(-1);// 创建Person对应的DataBinderDataBinder binder = new DataBinder(person);// 设置校验binder.setValidator(new PersonValidator());// 由于Person对象中的属性为空，所以校验不通过binder.validate();//输出结果BindingResult results = binder.getBindingResult();System.out.println(results.getAllErrors());}
}

实验二：Bean Validation注解实现

使用Bean Validation校验方式，就是如何将Bean Validation需要使用的javax.validation.ValidatorFactory 和javax.validation.Validator注入到容器中。spring默认有一个实现类LocalValidatorFactoryBean，它实现了上面Bean Validation中的接口，并且也实现了org.springframework.validation.Validator接口。

第一步 创建配置类，配置LocalValidatorFactoryBean

@Configuration
@ComponentScan("com.test.validation")
public class ValidationConfig {@Beanpublic LocalValidatorFactoryBean validator() {return new LocalValidatorFactoryBean();}
}

第二步 创建实体类，使用注解定义校验规则

import jakarta.validation.constraints.Max;
import jakarta.validation.constraints.Min;
import jakarta.validation.constraints.NotNull;public class User {@NotNullprivate String name;@Min(0)@Max(120)private int age;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

常用注解说明

@NotNull 限制必须不为null @NotEmpty 只作用于字符串类型，字符串不为空，并且长度不为0
@NotBlank 只作用于字符串类型，字符串不为空，并且trim()后不为空串
@DecimalMax(value) 限制必须为一个不大于指定值的数字
@DecimalMin(value) 限制必须为一个不小于指定值的数字 @Max(value) 限制必须为一个不大于指定值的数字
@Min(value) 限制必须为一个不小于指定值的数字 @Pattern(value) 限制必须符合指定的正则表达式
@Size(max,min) 限制字符长度必须在min到max之间
@Email 验证注解的元素值是Email，也可以通过正则表达式和flag指定自定义的email格式

第三步 使用两种不同的校验器实现

（1）使用jakarta.validation.Validator校验

import jakarta.validation.ConstraintViolation;
import jakarta.validation.Validator;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.Set;@Service
public class MyService1 {@Autowiredprivate Validator validator;public  boolean validator(User user){Set<ConstraintViolation<User>> sets =  validator.validate(user);return sets.isEmpty();}}

（2）使用org.springframework.validation.Validator校验

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.validation.BindException;
import org.springframework.validation.Validator;@Service
public class MyService2 {@Autowiredprivate Validator validator;public boolean validaPersonByValidator(User user) {BindException bindException = new BindException(user, user.getName());validator.validate(user, bindException);return bindException.hasErrors();}
}

第四步 测试

import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class TestMethod2 {@Testpublic void testMyService1() {ApplicationContext context = new AnnotationConfigApplicationContext(ValidationConfig.class);MyService1 myService = context.getBean(MyService1.class);User user = new User();user.setAge(-1);boolean validator = myService.validator(user);System.out.println(validator);}@Testpublic void testMyService2() {ApplicationContext context = new AnnotationConfigApplicationContext(ValidationConfig.class);MyService2 myService = context.getBean(MyService2.class);User user = new User();user.setName("lucy");user.setAge(130);user.setAge(-1);boolean validator = myService.validaPersonByValidator(user);System.out.println(validator);}
}

实验三：基于方法实现校验

第一步 创建配置类，配置MethodValidationPostProcessor

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;@Configuration
@ComponentScan("com.test.validation")
public class ValidationConfig {@Beanpublic MethodValidationPostProcessor validationPostProcessor() {return new MethodValidationPostProcessor();}
}

第二步 创建实体类，使用注解设置校验规则

import jakarta.validation.constraints.*;public class User {@NotNullprivate String name;@Min(0)@Max(120)private int age;@Pattern(regexp = "^1(3|4|5|7|8)\\d{9}$",message = "手机号码格式错误")@NotBlank(message = "手机号码不能为空")private String phone;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}
}

第三步 定义Service类，通过注解操作对象

import jakarta.validation.Valid;
import jakarta.validation.constraints.NotNull;
import org.springframework.stereotype.Service;
import org.springframework.validation.annotation.Validated;@Service
@Validated
public class MyService {public String testParams(@NotNull @Valid User user) {return user.toString();}}

第四步 测试

import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class TestMethod3 {@Testpublic void testMyService1() {ApplicationContext context = new AnnotationConfigApplicationContext(ValidationConfig.class);MyService myService = context.getBean(MyService.class);User user = new User();user.setAge(-1);myService.testParams(user);}
}

实验四：实现自定义校验

import jakarta.validation.Constraint;
import jakarta.validation.Payload;
import java.lang.annotation.*;@Target({ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE, ElementType.CONSTRUCTOR, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Constraint(validatedBy = {CannotBlankValidator.class})
public @interface CannotBlank {//默认错误消息String message() default "不能包含空格";//分组Class<?>[] groups() default {};//负载Class<? extends Payload>[] payload() default {};//指定多个时使用@Target({ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.TYPE_USE})@Retention(RetentionPolicy.RUNTIME)@Documented@interface List {CannotBlank[] value();}
}

第二步 编写真正的校验类

import jakarta.validation.ConstraintValidator;
import jakarta.validation.ConstraintValidatorContext;public class CannotBlankValidator implements ConstraintValidator<CannotBlank, String> {@Overridepublic void initialize(CannotBlank constraintAnnotation) {}@Overridepublic boolean isValid(String value, ConstraintValidatorContext context) {//null时不进行校验if (value != null && value.contains(" ")) {//获取默认提示信息String defaultConstraintMessageTemplate = context.getDefaultConstraintMessageTemplate();System.out.println("default message :" + defaultConstraintMessageTemplate);//禁用默认提示信息context.disableDefaultConstraintViolation();//设置提示语context.buildConstraintViolationWithTemplate("can not contains blank").addConstraintViolation();return false;}return true;}
}