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29-09-2019 - |
题
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,注释这样的集合是不可接受的。
有没有办法做到这一点?
解决方案
JSR-303和Hibernate验证器都没有任何现成的约束,可以验证收集的每个元素。
解决此问题的一种可能解决方案是创建一个自定义 @ValidCollection
约束和相应的验证器实现 ValidCollectionValidator
.
要验证收集的每个元素,我们需要一个实例 Validator
里面 ValidCollectionValidator
;为了获得这样的实例,我们需要自定义实施 ConstraintValidatorFactory
.
看看您是否喜欢以下解决方案...
简单地,
- 复制所有这些Java类(以及导入Relavent类);
- 在ClassPath上添加验证-API,hibenate-validator,slf4j-log4j12和testng jars;
- 运行测试案例。
验证
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 {};
}
palifcollectionValidator
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;
}
}
验证器contextawarecontaintaintvalidator
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; }
}
约束validatorFactoryImpl
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; }
}
palifcollectionTest
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}
笔记:- 当bean有约束时未指定 constraints
属性 @ValidCollection
约束。这 constraints
当Bean没有约束时,属性是必要的。
其他提示
不可能写出像 @EachElement
由于Java注释本身的限制,要包裹任何约束注释。但是,您可以编写一个通用约束验证器类,该类将每个元素的实际验证委托给现有约束验证器。您必须为每个约束写一个包装器注释,只是一个验证器。
我已经在 Jirutka/验证器收集 (可在Maven Central上使用)。例如:
@EachSize(min = 5, max = 255)
List<String> values;
该库允许您轻松创建一个“伪约束” 任何 验证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验证约束和休眠特定约束都支持约束。
创建一个 @EachAwesome
为了你自己的 @Awesome
约束,只需复制并粘贴注释类,替换 @Constraint
带注释 @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:更新了当前版本的库。
感谢BECOMPUTER06的出色答案。但是我认为应将以下注释添加到验证定义中:
@Target( { ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = ValidCollectionValidator.class)
而且,我仍然不喜欢如何处理原始类型包装器的集合,并约束@Size,@min,@max等的注释,因为无法通过Becomputer06的方式传递值。
当然,我可以为应用程序中的所有情况创建自定义的违反注释,但是无论如何,我必须将这些注释的属性添加到CollectionElementBean中。这似乎是一个足够糟糕的解决方案。
JSR-303具有扩展内置约束的目标类型的能力:请参阅 7.1.2。 XML中的重大约束定义.
您可以实现 ConstraintValidator<Email, List<String>>
与给定答案相同的事情,将其委派给原始验证器。然后,您可以保持模型定义并应用 @Email
上 List<String>
.
一个非常简单的解决方法是可能的。取而代之的是,您可以验证包装简单值属性的类的集合。为此,您需要使用 @Valid
收藏的注释。
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());
}
}