41

我希望能够做类似的事情：

@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。

有没有办法做到这一点？

4

6 回答 6

56

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

解决此问题的一种可能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，我们需要一个Validatorinside实例ValidCollectionValidator；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 classpath 上添加 validation-api、hibenate-validator、slf4j-log4j12 和 testng jar；
  • 运行测试用例。

有效集合

    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);

}

集合元素豆

    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; }

}

购物车

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; }

}

有效集合测试

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("me@gmail.com");

        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，不要指定约束的constraints属性@ValidCollection。constraints当 bean 没有约束时，该属性是必需的。

于 2010-12-01T20:55:04.920 回答
26

我没有足够高的声誉来评论这个原始答案，但也许在这个问题上值得注意的是，JSR-308处于最终发布阶段，并将在发布时解决这个问题！但是，它至少需要 Java 8。

唯一的区别是验证注释将进入类型声明。

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

请让我知道您认为我可以将这些信息放在哪里最适合其他正在寻找的人。谢谢！

PS 有关更多信息，请查看此 SO 帖子。

于 2015-08-03T21:16:08.807 回答
15

@EachElement由于 Java Annotations 本身的限制，不可能编写像包装任何约束注释那样的通用包装器注释。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注释，但只有一个验证器。

我已经在jirutka/validator-collection（在 Maven Central 中可用）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”以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。EachX所有标准 Bean Validation 约束和 Hibernate 特定约束都支持约束。

@EachAwesome要为您自己的约束创建一个@Awesome，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。

于 2013-04-15T19:14:26.657 回答
4

感谢 becomputer06 的精彩回答。但我认为应在 ValidCollection 定义中添加以下注释：

@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的集合并约束@Size、@Min、@Max 等注释，因为值不能通过 becomputer06 的方式传递。

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

于 2012-09-23T10:21:51.330 回答
1

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

您可以实现ConstraintValidator<Email, List<String>>与给定答案执行相同操作的 a，委托给原始验证器。然后你可以保留你的模型定义并应用@Email在List<String>.

于 2014-01-03T03:23:18.397 回答
0

一个非常简单的解决方法是可能的。您可以改为验证包含简单值属性的类的集合。为此，您需要@Valid在集合上使用注释。

例子：

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());
  }

}
于 2017-06-20T12:00:32.947 回答