基元集合的 Hibernate 验证

Question

我希望能够执行以下操作：

@Email
public List<String> getEmailAddresses()
{
   return this.emailAddresses;
}

换句话说，我希望列表中的每个项目都被验证为电子邮件地址。当然，像这样注释集合是不可接受的。

有办法做到这一点吗？

Answer 1

JSR-303 和 Hibernate Validator 都没有任何现成的约束来验证 Collection 的每个元素。

解决此问题的一种可能的解决方案是创建自定义 @ValidCollection 约束和相应的验证器实现 ValidCollectionValidator。

为了验证集合的每个元素，我们需要在 ValidCollectionValidator 内有一个 Validator 实例；为了获得这样的实例，我们需要自定义实现ConstraintValidatorFactory。

看看您是否喜欢以下解决方案...

简单地，

• 复制粘贴所有这些 java 类（并导入相关类）；
• 在类路径上添加validation-api、hibenate-validator、slf4j-log4j12和testng jar；
• 运行测试用例。

ValidCollection

    public @interface ValidCollection {

    Class<?> elementType();

    /* Specify constraints when collection element type is NOT constrained 
     * validator.getConstraintsForClass(elementType).isBeanConstrained(); */
    Class<?>[] constraints() default {};

    boolean allViolationMessages() default true;

    String message() default "{ValidCollection.message}";

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

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

}

ValidCollectionValidator

    public class ValidCollectionValidator implements ConstraintValidator<ValidCollection, Collection>, ValidatorContextAwareConstraintValidator {

    private static final Logger logger = LoggerFactory.getLogger(ValidCollectionValidator.class);

    private ValidatorContext validatorContext;

    private Class<?> elementType;
    private Class<?>[] constraints;
    private boolean allViolationMessages;

    @Override
    public void setValidatorContext(ValidatorContext validatorContext) {
        this.validatorContext = validatorContext;
    }

    @Override
    public void initialize(ValidCollection constraintAnnotation) {
        elementType = constraintAnnotation.elementType();
        constraints = constraintAnnotation.constraints();
        allViolationMessages = constraintAnnotation.allViolationMessages();
    }

    @Override
    public boolean isValid(Collection collection, ConstraintValidatorContext context) {
        boolean valid = true;

        if(collection == null) {
            //null collection cannot be validated
            return false;
        }

        Validator validator = validatorContext.getValidator();

        boolean beanConstrained = validator.getConstraintsForClass(elementType).isBeanConstrained();

        for(Object element : collection) {
            Set<ConstraintViolation<?>> violations = new HashSet<ConstraintViolation<?>> ();

            if(beanConstrained) {
                boolean hasValidCollectionConstraint = hasValidCollectionConstraint(elementType);
                if(hasValidCollectionConstraint) {
                    // elementType has @ValidCollection constraint
                    violations.addAll(validator.validate(element));
                } else {
                    violations.addAll(validator.validate(element));
                }
            } else {
                for(Class<?> constraint : constraints) {
                    String propertyName = constraint.getSimpleName();
                    propertyName = Introspector.decapitalize(propertyName);
                    violations.addAll(validator.validateValue(CollectionElementBean.class, propertyName, element));
                }
            }

            if(!violations.isEmpty()) {
                valid = false;
            }

            if(allViolationMessages) { //TODO improve
                for(ConstraintViolation<?> violation : violations) {
                    logger.debug(violation.getMessage());
                    ConstraintViolationBuilder violationBuilder = context.buildConstraintViolationWithTemplate(violation.getMessage());
                    violationBuilder.addConstraintViolation();
                }
            }

        }

        return valid;
    }

    private boolean hasValidCollectionConstraint(Class<?> beanType) {
        BeanDescriptor beanDescriptor = validatorContext.getValidator().getConstraintsForClass(beanType);
        boolean isBeanConstrained = beanDescriptor.isBeanConstrained();
        if(!isBeanConstrained) {
            return false;
        }
        Set<ConstraintDescriptor<?>> constraintDescriptors = beanDescriptor.getConstraintDescriptors(); 
        for(ConstraintDescriptor<?> constraintDescriptor : constraintDescriptors) {
            if(constraintDescriptor.getAnnotation().annotationType().getName().equals(ValidCollection.class.getName())) {
                return true;
            }
        }
        Set<PropertyDescriptor> propertyDescriptors = beanDescriptor.getConstrainedProperties();
        for(PropertyDescriptor propertyDescriptor : propertyDescriptors) {
            constraintDescriptors = propertyDescriptor.getConstraintDescriptors();
            for(ConstraintDescriptor<?> constraintDescriptor : constraintDescriptors) {
                if(constraintDescriptor.getAnnotation().annotationType().getName().equals(ValidCollection.class.getName())) {
                    return true;
                }
            }    
        }
        return false;
    }

}

ValidatorContextAwareConstraintValidator

public interface ValidatorContextAwareConstraintValidator {

    void setValidatorContext(ValidatorContext validatorContext);

}

CollectionElementBean

    public class CollectionElementBean {

    /* add more properties on-demand */
    private Object notNull;
    private String notBlank;
    private String email;

    protected CollectionElementBean() {
    }

    @NotNull
    public Object getNotNull() { return notNull; }
    public void setNotNull(Object notNull) { this.notNull = notNull; }

    @NotBlank
    public String getNotBlank() { return notBlank; }
    public void setNotBlank(String notBlank) { this.notBlank = notBlank; }

    @Email
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }

}

ConstraintValidatorFactoryImpl

public class ConstraintValidatorFactoryImpl implements ConstraintValidatorFactory {

    private ValidatorContext validatorContext;

    public ConstraintValidatorFactoryImpl(ValidatorContext nativeValidator) {
        this.validatorContext = nativeValidator;
    }

    @Override
    public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key) {
        T instance = null;

        try {
            instance = key.newInstance();
        } catch (Exception e) { 
            // could not instantiate class
            e.printStackTrace();
        }

        if(ValidatorContextAwareConstraintValidator.class.isAssignableFrom(key)) {
            ValidatorContextAwareConstraintValidator validator = (ValidatorContextAwareConstraintValidator) instance;
            validator.setValidatorContext(validatorContext);
        }

        return instance;
    }

}

员工

public class Employee {

    private String firstName;
    private String lastName;
    private List<String> emailAddresses;

    @NotNull
    public String getFirstName() { return firstName; }
    public void setFirstName(String firstName) { this.firstName = firstName; }

    public String getLastName() { return lastName; }
    public void setLastName(String lastName) { this.lastName = lastName; }

    @ValidCollection(elementType=String.class, constraints={Email.class})
    public List<String> getEmailAddresses() { return emailAddresses; }
    public void setEmailAddresses(List<String> emailAddresses) { this.emailAddresses = emailAddresses; }

}

团队

public class Team {

    private String name;
    private Set<Employee> members;

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    @ValidCollection(elementType=Employee.class)
    public Set<Employee> getMembers() { return members; }
    public void setMembers(Set<Employee> members) { this.members = members; }

}

ShoppingCart

public class ShoppingCart {

    private List<String> items;

    @ValidCollection(elementType=String.class, constraints={NotBlank.class})
    public List<String> getItems() { return items; }
    public void setItems(List<String> items) { this.items = items; }

}

ValidCollectionTest

public class ValidCollectionTest {

    private static final Logger logger = LoggerFactory.getLogger(ValidCollectionTest.class);

    private ValidatorFactory validatorFactory;

    @BeforeClass
    public void createValidatorFactory() {
        validatorFactory = Validation.buildDefaultValidatorFactory();
    }

    private Validator getValidator() {
        ValidatorContext validatorContext = validatorFactory.usingContext();
        validatorContext.constraintValidatorFactory(new ConstraintValidatorFactoryImpl(validatorContext));
        Validator validator = validatorContext.getValidator();
        return validator;
    }

    @Test
    public void beanConstrained() {
        Employee se = new Employee();
        se.setFirstName("Santiago");
        se.setLastName("Ennis");
        se.setEmailAddresses(new ArrayList<String> ());
        se.getEmailAddresses().add("segmail.com");
        Employee me = new Employee();
        me.setEmailAddresses(new ArrayList<String> ());
        me.getEmailAddresses().add("[email protected]");

        Team team = new Team();
        team.setMembers(new HashSet<Employee>());
        team.getMembers().add(se);
        team.getMembers().add(me);

        Validator validator = getValidator();

        Set<ConstraintViolation<Team>> violations = validator.validate(team);
        for(ConstraintViolation<Team> violation : violations) {
            logger.info(violation.getMessage());
        }
    }

    @Test
    public void beanNotConstrained() {
        ShoppingCart cart = new ShoppingCart();
        cart.setItems(new ArrayList<String> ());
        cart.getItems().add("JSR-303 Book");
        cart.getItems().add("");

        Validator validator = getValidator();

        Set<ConstraintViolation<ShoppingCart>> violations = validator.validate(cart, Default.class);
        for(ConstraintViolation<ShoppingCart> violation : violations) {
            logger.info(violation.getMessage());
        }
    }

}

输出

02:16:37,581  INFO main validation.ValidCollectionTest:66 - {ValidCollection.message}
02:16:38,303  INFO main validation.ValidCollectionTest:66 - may not be null
02:16:39,092  INFO main validation.ValidCollectionTest:66 - not a well-formed email address

02:17:46,460  INFO main validation.ValidCollectionTest:81 - may not be empty
02:17:47,064  INFO main validation.ValidCollectionTest:81 - {ValidCollection.message}

注意：- 当bean有约束时，不要指定@ValidCollection 约束的 >constraints 属性。当 bean 没有约束时，constraints 属性是必需的。

Answer 2

我没有足够高的声誉来对原始答案发表评论，但也许值得注意的是这个问题 JSR-308 正处于最终发布阶段，发布后将解决此问题！不过，它至少需要 Java 8。

唯一的区别是验证注释将位于类型声明内部。

//@Email
public List<@Email String> getEmailAddresses()
{
   return this.emailAddresses;
}

请告诉我您认为我可以最好地将这些信息放在哪里，以供其他正在寻找的人使用。谢谢！

PS：如需了解更多信息，请查看这篇文章。

Answer 3

由于 Java 注解本身的限制，不可能编写像 @EachElement 这样的通用包装器注解来包装任何约束注解。但是，您可以编写一个通用约束验证器类，它将每个元素的实际验证委托给现有的约束验证器。您必须为每个约束编写一个包装器注释，但只需一个验证器。

我已经在 jirutka/validator-collection （可在 Maven Central 中找到）中实现了这种方法。例如：

@EachSize(min = 5, max = 255)
List<String> values;

该库允许您轻松地为任何验证约束创建“伪约束”来注释简单类型的集合，而无需为每个集合编写额外的验证器或不必要的包装类。所有标准 Bean 验证约束和 Hibernate 特定约束都支持 EachX 约束。

要为您自己的 @Awesome 约束创建 @EachAwesome，只需复制并粘贴注释类，将 @Constraint 注释替换为 @ Constraint(validatedBy = CommonEachValidator.class) 并添加注释 @EachConstraint(validateAs = Awesome.class)。就这样！

// common boilerplate
@Documented
@Retention(RUNTIME)
@Target({METHOD, FIELD, ANNOTATION_TYPE})
// this is important!
@EachConstraint(validateAs = Awesome.class)
@Constraint(validatedBy = CommonEachValidator.class)
public @interface EachAwesome {

    // copy&paste all attributes from Awesome annotation here
    String message() default "";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
    String someAttribute();
}

编辑：针对当前版本的库进行了更新。

Answer 4

感谢 becomputer06 的精彩回答。
但我认为应该将以下注释添加到 ValidCollection 定义中：

@Target( { ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = ValidCollectionValidator.class)

而且我仍然不明白如何处理原始类型包装器和约束注释（如 @Size、@Min、@Max 等）的集合，因为值不能通过becomputer06的方式。

当然，我可以为应用程序中的所有情况创建自定义约束注释，但无论如何我必须将这些注释的属性添加到 CollectionElementBean。这似乎是一个足够糟糕的解决方案。

Answer 5

JSR-303 能够扩展内置约束的目标类型：请参阅 7.1.2 。覆盖 XML 中的约束定义。

您可以实现一个 ConstraintValidator> ，它与给定的答案执行相同的操作，委托给原始验证器。然后，您可以保留模型定义并在 List 上应用 @Email。

Answer 6

可以采用非常简单的解决方法。您可以改为验证包装简单值属性的类的集合。为此，您需要在集合上使用 @Valid 注释。

示例：

public class EmailAddress {

  @Email
  String email;

  public EmailAddress(String email){
    this.email = email;
  }
}

public class Foo {

  /* Validation that works */
  @Valid
  List<EmailAddress> getEmailAddresses(){
    return this.emails.stream().map(EmailAddress::new).collect(toList());
  }

}