Spring(十二)-Validation校验

参考文献

Spring校验使用场景

Spring常规校验(Validator)
Spring数据绑定(DataBinder)
Spring Web参数绑定(WebDataBinder)
Spring Web MVC/Spring WebFlux处理方法参数校验

`Validator`接口设计

接口职责
- Spring内部校验器接口,通过编程的方式校验目标对象
核心方法
- support(Class): 校验目标类能否校验;
- validate(Object,Errors): 校验目标对象,并将校验失败的内容输出至Errors对象
配套组件
- 错误收集器: org.springframework.validation.Errors
- Validator 工具类：org.springframework.validation.ValidationUtils

`Errors`接口设计

接口职责
- 数据绑定和校验错误收集接口，与 Java Bean 和其属性有强关联性
核心方法
- reject 方法（重载）：收集错误文案
- rejectValue 方法（重载）：收集对象字段中的错误文案
配套组件
- Java Bean 错误描述：org.springframework.validation.ObjectError
- Java Bean 属性错误描述：org.springframework.validation.FieldError

`Errors` 文案来源

Errors 文案生成步骤
- 选择 Errors实现（如：org.springframework.validation.BeanPropertyBindingResult）
- 调用 reject 或 rejectValue 方法
- 获取 Errors 对象中 ObjectError 或 FieldError
- 将 ObjectError 或 FieldError 中的 code 和 args，关联 MessageSource 实现（如:ResourceBundleMessageSource)

自定义 `Validator`

实现 org.springframework.validation.Validator 接口
- 实现 supports 方法
- 实现 validate 方法
  - 通过 Errors 对象收集错误
    - ObjectError：对象（Bean）错误：
    - FieldError：对象（Bean）属性（Property）错误
  - 通过 ObjectError 和 FieldError 关联 MessageSource 实现获取最终文案

`Validator` 的救赎

Bean Validation 与 Validator 适配
- 核心组件 - org.springframework.validation.beanvalidation.LocalValidatorFactoryBean
- 依赖 Bean Validation - JSR-303 or JSR-349 provider
- Bean 方法参数校验 - org.springframework.validation.beanvalidation.MethodValidationPostProcessor

`Hibernate Validator`

注解

注解名	支持类型	作用
`@Valid`		被注解的元素是一个对象,需要检查此对象的所有字段
`@AssertTrue`	`Boolean`, `boolean`	被注解的元素必须为true
`@AsserFalse`	`Boolean`, `boolean`	被注解的元素必须为false
`@Min(value)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须是一个数字,其值必须大于等于指定的最小值
`@Max(value)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须是一个数字,其值必须小于等于指定的最大值
`@DecimalMin(value)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须是一个数字,其值必须小于等于指定的最大值
`@DecimalMax(value)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须是一个数字,其值必须小于等于指定的最大值
`@Size(max,min)`		被注解的元素的大小必须在指定的范围内
`@Digits(integer,fraction)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须是一个数字,其值必须在可接受的范围内
`@Past`	`java.util.Date`,`java.util.Calendar`, `java.time.Instant`, `java.time.LocalDate`, `java.time.LocalDateTime`, `java.time.LocalTime`, `java.time.MonthDay`, `java.time.OffsetDateTime`, `java.time.OffsetTime`, `java.time.Year`, `java.time.YearMonth`, `java.time.ZonedDateTime`, `java.time.chrono.HijrahDate`, `java.time.chrono.JapaneseDate`, `java.time.chrono.MinguoDate`, `java.time.chrono.ThaiBuddhistDate`;	被注解的元素必须是一个过去的日期
`@PastOrPresent`	`java.util.Date`,`java.util.Calendar`, `java.time.Instant`, `java.time.LocalDate`, `java.time.LocalDateTime`, `java.time.LocalTime`, `java.time.MonthDay`, `java.time.OffsetDateTime`, `java.time.OffsetTime`, `java.time.Year`, `java.time.YearMonth`, `java.time.ZonedDateTime`, `java.time.chrono.HijrahDate`, `java.time.chrono.JapaneseDate`, `java.time.chrono.MinguoDate`, `java.time.chrono.ThaiBuddhistDate`;
`@Future`	`java.util.Date`, `java.util.Calendar`, `java.time.Instant`, `java.time.LocalDate`, `java.time.LocalDateTime`, `java.time.LocalTime`, `java.time.MonthDay`, `java.time.OffsetDateTime`, `java.time.OffsetTime`, `java.time.Year`, `java.time.YearMonth`, `java.time.ZonedDateTime`, `java.time.chrono.HijrahDate`, `java.time.chrono.JapaneseDate`, `java.time.chrono.MinguoDate`, `java.time.chrono.ThaiBuddhistDate`;	被注解的元素必须是一个将来的日期
`@FutureOrPresent`	`java.util.Date`, `java.util.Calendar`, `java.time.Instant`, `java.time.LocalDate`, `java.time.LocalDateTime`, `java.time.LocalTime`, `java.time.MonthDay`, `java.time.OffsetDateTime`, `java.time.OffsetTime`, `java.time.Year`, `java.time.YearMonth`, `java.time.ZonedDateTime`, `java.time.chrono.HijrahDate`, `java.time.chrono.JapaneseDate`, `java.time.chrono.MinguoDate`, `java.time.chrono.ThaiBuddhistDate`;	检查标注的日期是现在还是将来
`@Pattern(value)`		被注解的元素必须符合指定的正则表达式
`@Email`		被注解的元素必须是电子邮箱地址
`@Length(min=,max=)`	`CharSequence`	被注解的字符串的大小必须在指定的范围内
`@Range(min=,max=)`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	被注解的元素必须在可接受的范围内
`@Null`	Any type	被注解的元素必须为null
`@NotNull`	Any type	被注解的元素必须不为null
`@NotEmpty`	`CharSequence`, `Collection`, `Map` and `arrays`	被注解的元素必须非空
`@NotBlank`	`CharSequence`	被注解的元素必须非空
`@URL(protocol=,host=,port=,regexp=,flags=)`		被注解的元素必须是一个有效的URL
`@CreditCardNumber`		被注解的字符串必须通过Luhn校验算法,银行卡,信用卡等号码一般都用Luhn计算合法性
`@ScriptAssert(lang=,script=,alias=)`		要有Java Scripting API
`@SafeHtml(whitelistType,additionTags=)`		classpath中要有jsoup包
`@Negative`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	负数
`@NegativeOrZero`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	负数和0
`@Positive`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	正数
`@PositiveOrZero`	`BigDecimal, BigInteger, CharSequence ,byte, short, int, long` and the respective wrappers of the primitive types;	正数和0
`@DurationMax(days=, hours=, minutes=, seconds=, millis=, nanos=, inclusive=)`	`java.time.Duration` 前段参数传入参数以`PT`开头,如`PT1H30M`表示1小时30分钟的Duration值
`@DurationMin(days=, hours=, minutes=, seconds=, millis=, nanos=, inclusive=)`	`java.time.Duration`

@NotNull,@NotEmpty,@NotBlank三个注解的区别
- @NotNull:任何对象的value不能为null.
- @NotEmpty:集合对象元素不为0,即集合不为空,也可以用于字符串不为null.
- @NotBlank: 只能用于字符串不为null,并且字符串trim()以后length要大于0.

实战

`RequestBody`参数校验

POST,PUT请求一般会使用RequestBody传递参数，这种情况下，后端使用DTO对象进行接收。只要给DTO对象加上@Validated注解就能实现自动参数校验。
如果校验失败,会抛出MethodArgumentNotValidException异常，Spring默认会将其转为400(Bad Request)请求。

package com.holelin.sundry.vo.request;

import lombok.Data;
import org.hibernate.validator.constraints.Length;

import javax.validation.constraints.NotNull;

/**
 * @Description:
 * @Author: HoleLin
 * @CreateDate: 2022/7/18 22:55
 * @UpdateUser: HoleLin
 * @UpdateDate: 2022/7/18 22:55
 * @UpdateRemark: 修改内容
 * @Version: 1.0
 */
@Data
public class ValidTestOne {

    private Long userId;

    @NotNull
    @Length(min = 2, max = 10)
    private String userName;

    @NotNull
    @Length(min = 6, max = 20)
    private String account;

    @NotNull
    @Length(min = 6, max = 20)
    private String password;
}

package com.holelin.sundry.controller;

import com.holelin.sundry.vo.request.ValidTestOne;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Description:
 * @Author: HoleLin
 * @CreateDate: 2022/7/18 22:54
 * @UpdateUser: HoleLin
 * @UpdateDate: 2022/7/18 22:54
 * @UpdateRemark: 修改内容
 * @Version: 1.0
 */
@RestController
@RequestMapping("/valid-test")
public class ValidTestController {

    @RequestMapping("/test1")
    public void test1(@RequestBody @Validated ValidTestOne request){

    }
}

`RequestParam/PathVariable`参数校验

GET请求一般会使用RequestParam/PathVariable传参。如果参数比较多(比如超过6个)，还是推荐使用DTO对象接收。
否则，推荐将一个个参数平铺到方法入参中。在这种情况下，必须在Controller类上标注@Validated注解，并在入参上声明约束注解(如@Min等)。如果校验失败,会抛出ConstraintViolationException异常。

package com.holelin.sundry.controller;

import com.holelin.sundry.vo.request.ValidTestOne;
import org.hibernate.validator.constraints.Length;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;

/**
 * @Description:
 * @Author: HoleLin
 * @CreateDate: 2022/7/18 22:54
 * @UpdateUser: HoleLin
 * @UpdateDate: 2022/7/18 22:54
 * @UpdateRemark: 修改内容
 * @Version: 1.0
 */
@RestController
@Validated
@RequestMapping("/valid-test")
public class ValidTestController {
    /**
     * 路径变量
     *
     * @param userId
     */
    @GetMapping("/{userId}")
    public void test2(@PathVariable("userId") @Min(10000000000000000L) Long userId) {
    }


    /**
     * RequestParam
     * @param name
     */
    @GetMapping("/test3")
    public void test3(@RequestParam("name") @Length(min = 1, max = 10) @NotNull String name) {
    }
}

统一异常处理

如果校验失败，会抛出MethodArgumentNotValidException或者ConstraintViolationException异常。在实际项目开发中，通常会用统一异常处理来返回一个更友好的提示。

package com.holelin.gb.advice;

import com.alibaba.fastjson.JSON;
import com.holelin.gb.exception.ResultException;
import com.holelin.gb.reps.Result;
import com.holelin.gb.reps.ResultCode;
import com.holelin.gb.reps.ResultUtils;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.exception.ConstraintViolationException;
import org.springframework.context.annotation.Scope;
import org.springframework.context.annotation.ScopedProxyMode;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.validation.BindingResult;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

import javax.servlet.http.HttpServletRequest;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * ClassName: WebExceptionHandler
 * web异常处理类
 *
 * @author HoleLin
 * @version 1.0
 * @date 2019/10/5
 */
@RestControllerAdvice
@ResponseBody
@Slf4j
public class WebExceptionHandler implements ResponseBodyAdvice {
    private ThreadLocal<Object> modelHolder = new ThreadLocal<>();

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public Result handleIllegalParamException(MethodArgumentNotValidException e) {
        BindingResult bindingResult = e.getBindingResult();
        StringBuilder sb = new StringBuilder("校验失败:");
        // Map<String, String> errorMap = new HashMap<>(8);
        // 将校验错误字段和错误信息提取到map中
        // bindingResult.getFieldErrors().forEach(item -> errorMap.put(item.getField(),item.getDefaultMessage()));
        for (FieldError fieldError : bindingResult.getFieldErrors()) {
            sb.append(fieldError.getField()).append(":").append(fieldError.getDefaultMessage()).append(",");
        }
        return ResultUtils.warn(ResultCode.PARAMETER_ERROR, sb.toString());
    }
    
    @ExceptionHandler({ConstraintViolationException.class})
    public Result handleConstraintViolationException(ConstraintViolationException ex) {
        return ResultUtils.warn(ResultCode.PARAMETER_ERROR,ex.getMessage());
    }
    
    @ExceptionHandler(ResultException.class)
    public Result handleResultException(ResultException e, HttpServletRequest request) {
        log.debug("uri={} | requestBody={}", request.getRequestURI(),
                JSON.toJSONString(modelHolder.get()));
        return ResultUtils.warn(e.getResultCode());
    }

    @ExceptionHandler(IllegalArgumentException.class)
    public Result handleIllegalArgumentException(IllegalArgumentException e, HttpServletRequest request) {
        log.error("uri={} | requestBody={}", request.getRequestURI(),
                JSON.toJSONString(modelHolder.get()), e);
        return ResultUtils.warn(ResultCode.PARAMETER_ERROR);
    }
    @ExceptionHandler(NoSuchElementException.class)
    public Result handleNoSuchElementException(NoSuchElementException e, HttpServletRequest request) {
        log.error("uri={} | requestBody={}", request.getRequestURI(),
                JSON.toJSONString(modelHolder.get()), e);
        return ResultUtils.warn(ResultCode.RECORD_EXIST);
    }
    @InitBinder
    public void initBinder(WebDataBinder webDataBinder) {
        // ModelHolder 初始化
        modelHolder.set(webDataBinder.getTarget());
    }
    @Override
    public boolean supports(MethodParameter methodParameter, Class aClass) {
        return true;
    }

    @Override
    public Object beforeBodyWrite(Object body, MethodParameter methodParameter,
                                  MediaType mediaType, Class aClass,
                                  ServerHttpRequest serverHttpRequest,
                                  ServerHttpResponse serverHttpResponse) {
        // ModelHolder 清理
        modelHolder.remove();
        return body;
    }
}

分组校验

在实际项目中，可能多个方法需要使用同一个DTO类来接收参数，而不同方法的校验规则很可能是不一样的。这个时候，简单地在DTO类的字段上加约束注解无法解决这个问题。因此，Spring-Validation支持了分组校验的功能，专门用来解决这类问题。
使用同一个DTO类来校验不同场景的参数校验,常见的如新增和更新.

package com.holelin.sundry.vo.request;

import lombok.Data;
import org.hibernate.validator.constraints.Length;

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;

/**
 * @Description:
 * @Author: HoleLin
 * @CreateDate: 2022/7/18 22:55
 * @UpdateUser: HoleLin
 * @UpdateDate: 2022/7/18 22:55
 * @UpdateRemark: 修改内容
 * @Version: 1.0
 */
@Data
public class ValidTestOne {

    @Min(value = 10000000000000000L, groups = Update.class)
    private Long userId;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 2, max = 10, groups = {Save.class, Update.class})
    private String userName;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 6, max = 20, groups = {Save.class, Update.class})
    private String account;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 6, max = 20, groups = {Save.class, Update.class})
    private String password;

    /**
     * 保存的时候校验分组
     */
    public interface Save {
    }

    /**
     * 更新的时候校验分组
     */
    public interface Update {
    }
}

@PostMapping("/save")
public void save(@RequestBody @Validated(ValidTestOne.Save.class) ValidTestOne request) {
    // 校验通过，才会执行业务逻辑处理
}

@PostMapping("/update")
public void update(@RequestBody @Validated(ValidTestOne.Update.class) ValidTestOne request) {
    // 校验通过，才会执行业务逻辑处理
}

嵌套校验

DTO类里面的字段都是基本数据类型和String类型。但是实际场景中，有可能某个字段也是一个对象，这种情况先，可以使用嵌套校验。
需要注意的是，此时DTO类的对应字段必须标记@Valid注解。
嵌套校验可以结合分组校验一起使用。还有就是嵌套集合校验会对集合里面的每一项都进行校验，例如List<Job>字段会对这个list里面的每一个Job对象都进行校验

@Data
public class UserDTO {

    @Min(value = 10000000000000000L, groups = Update.class)
    private Long userId;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 2, max = 10, groups = {Save.class, Update.class})
    private String userName;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 6, max = 20, groups = {Save.class, Update.class})
    private String account;

    @NotNull(groups = {Save.class, Update.class})
    @Length(min = 6, max = 20, groups = {Save.class, Update.class})
    private String password;

    @NotNull(groups = {Save.class, Update.class})
  	// 校验复制参数
    @Valid
    private Job job;

    @Data
    public static class Job {

        @Min(value = 1, groups = Update.class)
        private Long jobId;

        @NotNull(groups = {Save.class, Update.class})
        @Length(min = 2, max = 10, groups = {Save.class, Update.class})
        private String jobName;

        @NotNull(groups = {Save.class, Update.class})
        @Length(min = 2, max = 10, groups = {Save.class, Update.class})
        private String position;
    }

    /**
     * 保存的时候校验分组
     */
    public interface Save {
    }

    /**
     * 更新的时候校验分组
     */
    public interface Update {
    }
}

源码

入口:org.springframework.web.method.support.InvocableHandlerMethod#invokeForRequest
...中间略
org.hibernate.validator.internal.metadata.BeanMetaDataManagerImpl#getBeanMetaData
-->
org.hibernate.validator.internal.metadata.BeanMetaDataManagerImpl#createBeanMetaData
--> 
org.hibernate.validator.internal.metadata.BeanMetaDataManagerImpl#getBeanConfigurationForHierarchy
--> 
org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider#getBeanConfiguration
-->
retrieveBeanConfiguration
--> 
org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider#getFieldMetaData
-->
org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider#findPropertyMetaData
-->
org.hibernate.validator.internal.metadata.provider.AnnotationMetaDataProvider#findCascadingMetaData(org.hibernate.validator.internal.properties.javabean.JavaBeanField)

	private CascadingMetaDataBuilder getCascadingMetaData(JavaBeanAnnotatedElement annotatedElement,
			Map<TypeVariable<?>, CascadingMetaDataBuilder> containerElementTypesCascadingMetaData) {
    // 在组装 BeanMetaData 过程中，会根据成员字段是否标记了 @Valid 来决定（记录）这个 
字段以后是否做级联校验
		return CascadingMetaDataBuilder.annotatedObject( annotatedElement.getType(), annotatedElement.isAnnotationPresent( Valid.class ),
				containerElementTypesCascadingMetaData, getGroupConversions( annotatedElement.getAnnotatedType() ) );
	}

集合校验

如果请求体直接传递了json数组给后台，并希望对数组中的每一项都进行参数校验。此时，如果我们直接使用java.util.Collection下的list或者set来接收数据，参数校验并不会生效！我们可以使用自定义list集合来接收参数:包装List类型，并声明@Valid注解
@Delegate注解受lombok版本限制,1.18.6以上版本可支持.如果校验不通过,会抛出NotReadablePropertyException，同样可以使用统一异常进行处理。

public class ValidationList<E> implements List<E> {

    @Delegate // @Delegate是lombok注解
    @Valid // 一定要加@Valid注解
    public List<E> list = new ArrayList<>();

    // 一定要记得重写toString方法
    @Override
    public String toString() {
        return list.toString();
    }
}

@PostMapping("/saveList")
public Result saveList(@RequestBody @Validated(UserDTO.Save.class) ValidationList<UserDTO> userList) {
    // 校验通过，才会执行业务逻辑处理
    return Result.ok();
}

自定义校验

业务需求总是比框架提供的这些简单校验要复杂的多，我们可以自定义校验来满足我们的需求。

自定义Spring Validation非常简单，假设我们自定义加密id(由数字或者a-f的字母组成，32-256长度)校验，主要分为两步:

自定义约束注解

@Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER})
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {EncryptIdValidator.class})
public @interface EncryptId {

    // 默认错误消息
    String message() default "加密id格式错误";

    // 分组
    Class<?>[] groups() default {};

    // 负载
    Class<? extends Payload>[] payload() default {};
}

实现ConstraintValidator接口编写约束校验器

public class EncryptIdValidator implements ConstraintValidator<EncryptId, String> {

    private static final Pattern PATTERN = Pattern.compile("^[a-f\\d]{32,256}$");

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        // 不为null才进行校验
        if (value != null) {
            Matcher matcher = PATTERN.matcher(value);
            return matcher.find();
        }
        return true;
    }
}

校验枚举类

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 校验请求参数中的枚举类
 */
@Target(ElementType.FIELD) //METHOD, CONSTRUCTOR, etc.
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = EnumValidator.class)
public @interface ValidateEnum {
    String message() default "invalidParam";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
    Class<? extends Enum<?>> targetClassType();
}

import org.apache.commons.lang3.StringUtils;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.util.EnumSet;
import java.util.Set;
import java.util.stream.Collectors;

public class EnumValidator implements ConstraintValidator<ValidateEnum, String> {
    private Set<String> allowedValues;

    @SuppressWarnings({"unchecked", "rawtypes"})
    @Override
    public void initialize(ValidateEnum targetEnum) {
        Class<? extends Enum> enumSelected = targetEnum.targetClassType();
        allowedValues = (Set<String>) EnumSet.allOf(enumSelected).stream().map(e -> ((Enum<? extends Enum<?>>) e).name())
                .collect(Collectors.toSet());
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if (StringUtils.isEmpty(value)) {
            return true;
        }
        return allowedValues.contains(value);
    }
}

编程式校验

在某些情况下，我们可能希望以编程方式调用验证。这个时候可以注入javax.validation.Validator对象，然后再调用其api。

@Autowired
private javax.validation.Validator globalValidator;

// 编程式校验
@PostMapping("/saveWithCodingValidate")
public Result saveWithCodingValidate(@RequestBody UserDTO userDTO) {
    Set<ConstraintViolation<UserDTO>> validate = globalValidator.validate(userDTO, UserDTO.Save.class);
    // 如果校验通过，validate为空；否则，validate包含未校验通过项
    if (validate.isEmpty()) {
        // 校验通过，才会执行业务逻辑处理

    } else {
        for (ConstraintViolation<UserDTO> userDTOConstraintViolation : validate) {
            // 校验失败，做其它逻辑
            System.out.println(userDTOConstraintViolation);
        }
    }
    return Result.ok();
}

快速失败(`Fail Fast`)

Spring Validation默认会校验完所有字段，然后才抛出异常。可以通过一些简单的配置，开启Fali Fast模式，一旦校验失败就立即返回。

@Bean
public Validator validator() {
    ValidatorFactory validatorFactory = Validation.byProvider(HibernateValidator.class)
            .configure()
            // 快速失败模式
            .failFast(true)
            .buildValidatorFactory();
    return validatorFactory.getValidator();
}

`@Valid`和`@Validated`区别

区别	`@Valid`	`@Validated`
提供者	JSR-303规范	Spring
是否支持分组	不支持	支持
标注位置	`ElementType.METHOD, ElementType.FIELD, ElementType.CONSTRUCTOR, ElementType.PARAMETER, ElementType.TYPE_USE`	`ElementType.TYPE, ElementType.METHOD, ElementType.PARAMETER`
嵌套校验	支持	不支持

实现原理

在Spring-MVC中，RequestResponseBodyMethodProcessor是用于解析@RequestBody标注的参数以及处理@ResponseBody标注方法的返回值的.显然,执行参数校验的逻辑肯定就在解析参数的方法resolveArgument()中：

/**
 * Throws MethodArgumentNotValidException if validation fails.
 * @throws HttpMessageNotReadableException if {@link RequestBody#required()}
 * is {@code true} and there is no body content or if there is no suitable
 * converter to read the content with.
 */
@Override
public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
		NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
  
	parameter = parameter.nestedIfOptional();
   // 将请求封装到对应的DTO对象中
	Object arg = readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());
	String name = Conventions.getVariableNameForParameter(parameter);
  
	if (binderFactory != null) {
		WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
		if (arg != null) {
       // 执行数据校验
			validateIfApplicable(binder, parameter);
			if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
				throw new MethodArgumentNotValidException(parameter, binder.getBindingResult());
			}
		}
		if (mavContainer != null) {
			mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
		}
	}
  
	return adaptArgumentIfNecessary(arg, parameter);
}

  
/**
 * Validate the binding target if applicable.
 * <p>The default implementation checks for {@code @javax.validation.Valid},
 * Spring's {@link org.springframework.validation.annotation.Validated},
 * and custom annotations whose name starts with "Valid".
 * @param binder the DataBinder to be used
 * @param parameter the method parameter descriptor
 * @since 4.1.5
 * @see #isBindExceptionRequired
 */
protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {
   // 获取参数注解，比如@RequestBody、@Valid、@Validated
	Annotation[] annotations = parameter.getParameterAnnotations();
	for (Annotation ann : annotations) {
		Object[] validationHints = ValidationAnnotationUtils.determineValidationHints(ann);
		if (validationHints != null) {
			binder.validate(validationHints);
			break;
		}
	}
}

/**
 * Determine any validation hints by the given annotation.
 * <p>This implementation checks for {@code @javax.validation.Valid},
 * Spring's {@link org.springframework.validation.annotation.Validated},
 * and custom annotations whose name starts with "Valid".
 * @param ann the annotation (potentially a validation annotation)
 * @return the validation hints to apply (possibly an empty array),
 * or {@code null} if this annotation does not trigger any validation
 */
@Nullable
public static Object[] determineValidationHints(Annotation ann) {
	Class<? extends Annotation> annotationType = ann.annotationType();
	String annotationName = annotationType.getName();
	if ("javax.validation.Valid".equals(annotationName)) {
		return EMPTY_OBJECT_ARRAY;
	}
	Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class);
	if (validatedAnn != null) {
		Object hints = validatedAnn.value();
		return convertValidationHints(hints);
	}
	if (annotationType.getSimpleName().startsWith("Valid")) {
		Object hints = AnnotationUtils.getValue(ann);
		return convertValidationHints(hints);
	}
	return null;
}

/**
 * Invoke the specified Validators, if any, with the given validation hints.
 * <p>Note: Validation hints may get ignored by the actual target Validator.
 * @param validationHints one or more hint objects to be passed to a {@link SmartValidator}
 * @since 3.1
 * @see #setValidator(Validator)
 * @see SmartValidator#validate(Object, Errors, Object...)
 */
public void validate(Object... validationHints) {
	Object target = getTarget();
	Assert.state(target != null, "No target to validate");
	BindingResult bindingResult = getBindingResult();
	// Call each validator with the same binding result
	for (Validator validator : getValidators()) {
		if (!ObjectUtils.isEmpty(validationHints) && validator instanceof SmartValidator) {
			((SmartValidator) validator).validate(target, bindingResult, validationHints);
		}
		else if (validator != null) {
			validator.validate(target, bindingResult);
		}
	}
}

方法级别的参数校验实现原理

上面提到的将参数一个个平铺到方法参数中，然后在每个参数前面声明约束注解的校验方式，就是方法级别的参数校验。

实际上，这种方式可用于任何Spring Bean的方法上，比如Controller/Service等。其底层实现原理就是AOP，具体来说是通过MethodValidationPostProcessor动态注册AOP切面，然后使用MethodValidationInterceptor对切点方法织入增强。

public class MethodValidationPostProcessor extends AbstractBeanFactoryAwareAdvisingPostProcessor
		implements InitializingBean {

	private Class<? extends Annotation> validatedAnnotationType = Validated.class;

	@Nullable
	private Validator validator;
	// ...略

	@Override
	public void afterPropertiesSet() {
    //为所有@Validated标注的Bean创建切面
		Pointcut pointcut = new AnnotationMatchingPointcut(this.validatedAnnotationType, true);
    // 创建Advisor进行增强
		this.advisor = new DefaultPointcutAdvisor(pointcut, createMethodValidationAdvice(this.validator));
	}

	/**
	 * Create AOP advice for method validation purposes, to be applied
	 * with a pointcut for the specified 'validated' annotation.
	 * @param validator the JSR-303 Validator to delegate to
	 * @return the interceptor to use (typically, but not necessarily,
	 * a {@link MethodValidationInterceptor} or subclass thereof)
	 * @since 4.2
	 */
	protected Advice createMethodValidationAdvice(@Nullable Validator validator) {
		return (validator != null ? new MethodValidationInterceptor(validator) : new MethodValidationInterceptor());
	}

}

public class MethodValidationInterceptor implements MethodInterceptor {

	private final Validator validator;

	@Override
	@Nullable
	public Object invoke(MethodInvocation invocation) throws Throwable {
		// Avoid Validator invocation on FactoryBean.getObjectType/isSingleton
    // 无需增强的方法，直接跳过
		if (isFactoryBeanMetadataMethod(invocation.getMethod())) {
			return invocation.proceed();
		}
		// 获取分组信息
		Class<?>[] groups = determineValidationGroups(invocation);

		// Standard Bean Validation 1.1 API
		ExecutableValidator execVal = this.validator.forExecutables();
		Method methodToValidate = invocation.getMethod();
		Set<ConstraintViolation<Object>> result;

		Object target = invocation.getThis();
		Assert.state(target != null, "Target must not be null");

		try {
      
			result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
		}
		catch (IllegalArgumentException ex) {
			// Probably a generic type mismatch between interface and impl as reported in SPR-12237 / HV-1011
			// Let's try to find the bridged method on the implementation class...
			methodToValidate = BridgeMethodResolver.findBridgedMethod(
					ClassUtils.getMostSpecificMethod(invocation.getMethod(), target.getClass()));
			result = execVal.validateParameters(target, methodToValidate, invocation.getArguments(), groups);
		}
		if (!result.isEmpty()) {
			throw new ConstraintViolationException(result);
		}

		Object returnValue = invocation.proceed();

		result = execVal.validateReturnValue(target, methodToValidate, returnValue, groups);
		if (!result.isEmpty()) {
			throw new ConstraintViolationException(result);
		}

		return returnValue;
	}
  
  	private boolean isFactoryBeanMetadataMethod(Method method) {
		Class<?> clazz = method.getDeclaringClass();

		// Call from interface-based proxy handle, allowing for an efficient check?
		if (clazz.isInterface()) {
			return ((clazz == FactoryBean.class || clazz == SmartFactoryBean.class) &&
					!method.getName().equals("getObject"));
		}

		// Call from CGLIB proxy handle, potentially implementing a FactoryBean method?
		Class<?> factoryBeanType = null;
		if (SmartFactoryBean.class.isAssignableFrom(clazz)) {
			factoryBeanType = SmartFactoryBean.class;
		}
		else if (FactoryBean.class.isAssignableFrom(clazz)) {
			factoryBeanType = FactoryBean.class;
		}
		return (factoryBeanType != null && !method.getName().equals("getObject") &&
				ClassUtils.hasMethod(factoryBeanType, method));
	}
  
	/**
	 * Determine the validation groups to validate against for the given method invocation.
	 * <p>Default are the validation groups as specified in the {@link Validated} annotation
	 * on the containing target class of the method.
	 * @param invocation the current MethodInvocation
	 * @return the applicable validation groups as a Class array
	 */
	protected Class<?>[] determineValidationGroups(MethodInvocation invocation) {
		Validated validatedAnn = AnnotationUtils.findAnnotation(invocation.getMethod(), Validated.class);
		if (validatedAnn == null) {
			Object target = invocation.getThis();
			Assert.state(target != null, "Target must not be null");
			validatedAnn = AnnotationUtils.findAnnotation(target.getClass(), Validated.class);
		}
		return (validatedAnn != null ? validatedAnn.value() : new Class<?>[0]);
	}
}

参考文献

Spring校验使用场景

Validator接口设计

Errors接口设计

Errors 文案来源

自定义 Validator

Validator 的救赎

Hibernate Validator

注解

实战

RequestBody参数校验

RequestParam/PathVariable参数校验