深入了解数据校验（Bean Validation）：从深处去掌握@Valid的作用（级联校验）以及常用约束注解的解释说明【享学Java】

@Getter
@Setter
@ToString
public class Person {
    // 错误消息message是可以自定义的
    @NotNull(message = "{message} -> 名字不能为null", groups = Simple.class)
    public String name;
    @Max(value = 10, groups = Simple.class)
    @Positive(groups = Default.class) // 内置的分组：default
    public Integer age;

    @NotNull(groups = Complex.class)
    @NotEmpty(groups = Complex.class)
    private List<@Email String> emails;
    @Future(groups = Complex.class)
    private Date start;

    // 定义两个组 Simple组和Complex组
    interface Simple {
    }
    interface Complex {

    }
}

    public static void main(String[] args) {
        Person person = new Person();
        //person.setName("fsx");
        person.setAge(18);
        // email校验：虽然是List都可以校验哦
        person.setEmails(Arrays.asList("fsx@gmail.com", "baidu@baidu.com", "aaa.com"));
        //person.setStart(new Date()); //start 需要是一个将来的时间: Sun Jul 21 10:45:03 CST 2019
        //person.setStart(new Date(System.currentTimeMillis() + 10000)); //校验通过

        HibernateValidatorConfiguration configure = Validation.byProvider(HibernateValidator.class).configure();
        ValidatorFactory validatorFactory = configure.failFast(false).buildValidatorFactory();
        // 根据validatorFactory拿到一个Validator
        Validator validator = validatorFactory.getValidator();


        // 分组校验（可以区分对待Default组、Simple组、Complex组）
        Set<ConstraintViolation<Person>> result = validator.validate(person, Person.Simple.class);
        //Set<ConstraintViolation<Person>> result = validator.validate(person, Person.Complex.class);

        // 对结果进行遍历输出
        result.stream().map(v -> v.getPropertyPath() + " " + v.getMessage() + ": " + v.getInvalidValue())
                .forEach(System.out::println);

    }

age 最大不能超过10: 18
name {message} -> 名字不能为null -> 名字不能为null: null

public enum ConfigurationSource {
	ANNOTATION( 0 ),
	XML( 1 ),
	API( 2 ); //programmatic API
}

public interface MetaDataProvider {

	// 将**注解处理选项**归还给此Provider配置。  它的唯一实现类为：AnnotationProcessingOptionsImpl
	// 它可以配置比如：areMemberConstraintsIgnoredFor  areReturnValueConstraintsIgnoredFor
	// 也就说可以配置：让免于被校验~~~~~~(开绿灯用的)
	AnnotationProcessingOptions getAnnotationProcessingOptions();
	// 返回作用在此Bean上面的`BeanConfiguration`   若没有就返回null了
	// BeanConfiguration持有ConfigurationSource的引用~
	<T> BeanConfiguration<? super T> getBeanConfiguration(Class<T> beanClass);
	
}

// 表示源于一个ConfigurationSource的一个Java类型的完整约束相关配置。  包含字段、方法、类级别上的元数据
// 当然还包含有默认组序列上的元数据（使用较少）
public class BeanConfiguration<T> {
	// 三种来源的枚举
	private final ConfigurationSource source;
	private final Class<T> beanClass;
	// ConstrainedElement表示待校验的元素，可以知道它会如下四个子类：
	// ConstrainedField/ConstrainedType/ConstrainedParameter/ConstrainedExecutable
	
	// 注意：ConstrainedExecutable持有的是java.lang.reflect.Executable对象
	//它的两个子类是java.lang.reflect.Method和Constructor
	private final Set<ConstrainedElement> constrainedElements;

	private final List<Class<?>> defaultGroupSequence;
	private final DefaultGroupSequenceProvider<? super T> defaultGroupSequenceProvider;
	... // 它自己并不处理什么逻辑，参数都是通过构造器传进来的
}

public class AnnotationMetaDataProvider implements MetaDataProvider {

	private final ConstraintHelper constraintHelper;
	private final TypeResolutionHelper typeResolutionHelper;
	private final AnnotationProcessingOptions annotationProcessingOptions;
	private final ValueExtractorManager valueExtractorManager;

	// 这是一个非常重要的属性，它会记录着当前Bean  所有的待校验的Bean信息~~~
	private final BeanConfiguration<Object> objectBeanConfiguration;

	// 唯一构造函数
	public AnnotationMetaDataProvider(ConstraintHelper constraintHelper,
			TypeResolutionHelper typeResolutionHelper,
			ValueExtractorManager valueExtractorManager,
			AnnotationProcessingOptions annotationProcessingOptions) {
		this.constraintHelper = constraintHelper;
		this.typeResolutionHelper = typeResolutionHelper;
		this.valueExtractorManager = valueExtractorManager;
		this.annotationProcessingOptions = annotationProcessingOptions;

		// 默认情况下，它去把Object相关的所有的方法都retrieve:检索出来放着  我比较费解这件事~~~  
		// 后面才发现：一切为了效率
		this.objectBeanConfiguration = retrieveBeanConfiguration( Object.class );
	}

	// 实现接口方法
	@Override
	public AnnotationProcessingOptions getAnnotationProcessingOptions() {
		return new AnnotationProcessingOptionsImpl();
	}


	// 如果你的Bean是Object  就直接返回了~~~（大多数情况下  都是Object）
	@Override
	@SuppressWarnings("unchecked")
	public <T> BeanConfiguration<T> getBeanConfiguration(Class<T> beanClass) {
		if ( Object.class.equals( beanClass ) ) {
			return (BeanConfiguration<T>) objectBeanConfiguration;
		}
		return retrieveBeanConfiguration( beanClass );
	}
}

	private <T> BeanConfiguration<T> retrieveBeanConfiguration(Class<T> beanClass) {
		// 它检索的范围是：clazz.getDeclaredFields()  什么意思：就是搜集到本类所有的字段  包括private等等  但是不包括父类的所有字段
		Set<ConstrainedElement> constrainedElements = getFieldMetaData( beanClass );
		constrainedElements.addAll( getMethodMetaData( beanClass ) );
		constrainedElements.addAll( getConstructorMetaData( beanClass ) );

		//TODO GM: currently class level constraints are represented by a PropertyMetaData. This
		//works but seems somewhat unnatural
		// 这个TODO很有意思：当前，类级约束由PropertyMetadata表示。这是可行的，但似乎有点不自然
		// ReturnValueMetaData、ExecutableMetaData、ParameterMetaData、PropertyMetaData

		// 总之吧：此处就是把类级别的校验器放进来了（这个set大部分时候都是空的）
		Set<MetaConstraint<?>> classLevelConstraints = getClassLevelConstraints( beanClass );
		if (!classLevelConstraints.isEmpty()) {
			ConstrainedType classLevelMetaData = new ConstrainedType(ConfigurationSource.ANNOTATION, beanClass, classLevelConstraints);
			constrainedElements.add(classLevelMetaData);
		}
		
		// 组装成一个BeanConfiguration返回
		return new BeanConfiguration<>(ConfigurationSource.ANNOTATION, beanClass,
				constrainedElements, 
				getDefaultGroupSequence( beanClass ),  //此类上标注的所有@GroupSequence注解
				getDefaultGroupSequenceProvider( beanClass ) // 此类上标注的所有@GroupSequenceProvider注解
		);
	}

	// type解释：分如下N中情况
	// Field为：.getGenericType() // 字段的类型
	// Method为：.getGenericReturnType() // 返回值类型
	// Constructor：.getDeclaringClass() // 构造器所在类

	// annotatedElement：可不一定说一定要有注解才能进来（每个字段、方法、构造器等都能传进来）
	private CascadingMetaDataBuilder getCascadingMetaData(Type type, AnnotatedElement annotatedElement, Map<TypeVariable<?>, CascadingMetaDataBuilder> containerElementTypesCascadingMetaData) {
		return CascadingMetaDataBuilder.annotatedObject( type, annotatedElement.isAnnotationPresent( Valid.class ), containerElementTypesCascadingMetaData, getGroupConversions( annotatedElement ) );
	}

public abstract class ConstraintTree<A extends Annotation> {
	...
	protected final <T, V> Set<ConstraintViolation<T>> validateSingleConstraint(ValidationContext<T> executionContext,
			ValueContext<?, ?> valueContext,
			ConstraintValidatorContextImpl constraintValidatorContext,
			ConstraintValidator<A, V> validator) {
		...
		V validatedValue = (V) valueContext.getCurrentValidatedValue();
		isValid = validator.isValid( validatedValue, constraintValidatorContext );
		...
		// 显然校验不通过就返回错误消息  否则返回空集合
		if ( !isValid ) {
			return executionContext.createConstraintViolations(valueContext, constraintValidatorContext);
		}
		return Collections.emptySet();
	}
	...
}

success = metaConstraint.validateConstraint( validationContext, valueContext );

// ConstraintTree<A>
boolean validationResult = constraintTree.validateConstraints( executionContext, valueContext );

@Getter
@Setter
@ToString
public class Person {

    @NotNull
    private String name;
    @NotNull
    @Positive
    private Integer age;
    @Valid
    @NotNull
    private InnerChild child;

    @Getter
    @Setter
    @ToString
    public static class InnerChild {
        @NotNull
        private String name;
        @NotNull
        @Positive
        private Integer age;
    }

}

    public static void main(String[] args) {
        Person person = new Person();
        person.setName("fsx");
        Person.InnerChild child = new Person.InnerChild();
        child.setName("fsx-son");
        child.setAge(-1);
        person.setChild(child); // 放进去

        Validator validator = Validation.byProvider(HibernateValidator.class).configure().failFast(false)
                .buildValidatorFactory().getValidator();
        Set<ConstraintViolation<Person>> result = validator.validate(person);

        // 输出错误消息
        result.stream().map(v -> v.getPropertyPath() + " " + v.getMessage() + ": " + v.getInvalidValue())
                .forEach(System.out::println);
    }

child.age 必须是正数: -1
age 不能为null: null

@Repeatable(List.class)

javax.validation.constraints.AssertFalse.message     = 只能为false
javax.validation.constraints.AssertTrue.message      = 只能为true
javax.validation.constraints.DecimalMax.message      = 必须小于或等于{value}
javax.validation.constraints.DecimalMin.message      = 必须大于或等于{value}
javax.validation.constraints.Digits.message          = 数字的值超出了允许范围(只允许在{integer}位整数和{fraction}位小数范围内)
javax.validation.constraints.Email.message           = 不是一个合法的电子邮件地址
javax.validation.constraints.Future.message          = 需要是一个将来的时间
javax.validation.constraints.FutureOrPresent.message = 需要是一个将来或现在的时间
javax.validation.constraints.Max.message             = 最大不能超过{value}
javax.validation.constraints.Min.message             = 最小不能小于{value}
javax.validation.constraints.Negative.message        = 必须是负数
javax.validation.constraints.NegativeOrZero.message  = 必须是负数或零
javax.validation.constraints.NotBlank.message        = 不能为空
javax.validation.constraints.NotEmpty.message        = 不能为空
javax.validation.constraints.NotNull.message         = 不能为null
javax.validation.constraints.Null.message            = 必须为null
javax.validation.constraints.Past.message            = 需要是一个过去的时间
javax.validation.constraints.PastOrPresent.message   = 需要是一个过去或现在的时间
javax.validation.constraints.Pattern.message         = 需要匹配正则表达式"{regexp}"
javax.validation.constraints.Positive.message        = 必须是正数
javax.validation.constraints.PositiveOrZero.message  = 必须是正数或零
javax.validation.constraints.Size.message            = 个数必须在{min}和{max}之间

org.hibernate.validator.constraints.CreditCardNumber.message        = 不合法的信用卡号码
org.hibernate.validator.constraints.Currency.message                = 不合法的货币 (必须是{value}其中之一)
org.hibernate.validator.constraints.EAN.message                     = 不合法的{type}条形码
org.hibernate.validator.constraints.Email.message                   = 不是一个合法的电子邮件地址
org.hibernate.validator.constraints.Length.message                  = 长度需要在{min}和{max}之间
org.hibernate.validator.constraints.CodePointLength.message         = 长度需要在{min}和{max}之间
org.hibernate.validator.constraints.LuhnCheck.message               = ${validatedValue}的校验码不合法, Luhn模10校验和不匹配
org.hibernate.validator.constraints.Mod10Check.message              = ${validatedValue}的校验码不合法, 模10校验和不匹配
org.hibernate.validator.constraints.Mod11Check.message              = ${validatedValue}的校验码不合法, 模11校验和不匹配
org.hibernate.validator.constraints.ModCheck.message                = ${validatedValue}的校验码不合法, ${modType}校验和不匹配
org.hibernate.validator.constraints.NotBlank.message                = 不能为空
org.hibernate.validator.constraints.NotEmpty.message                = 不能为空
org.hibernate.validator.constraints.ParametersScriptAssert.message  = 执行脚本表达式"{script}"没有返回期望结果
org.hibernate.validator.constraints.Range.message                   = 需要在{min}和{max}之间
org.hibernate.validator.constraints.SafeHtml.message                = 可能有不安全的HTML内容
org.hibernate.validator.constraints.ScriptAssert.message            = 执行脚本表达式"{script}"没有返回期望结果
org.hibernate.validator.constraints.URL.message                     = 需要是一个合法的URL