Hibernate ClassValidator实例
Hibernate有很多值得学习的地方，这里我们主要介绍Hibernate ClassValidator实例，包括介绍Spring MVC 控制器使用的 CreditCardValidator等方面。
创建一个Hibernate ClassValidator实例
这个类进行实例化的代价可能会很高，因此最好只对希望进行验证的每个类来进行实例化。一种方法是创建一个实用工具类，对每个模型对象存储一个Hibernate ClassValidator实例，如下所示：
处理验证的实用工具类
/**
* Handles validations based on the Hibernate Annotations Validator framework.
* @author Ted Bergeron
* @version $Id: AnnotationValidator.java,v 1.5 2006/01/20 17:34:09 ted Exp $
*/
public class AnnotationValidator {
private static Log log = LogFactory.getLog(AnnotationValidator.class);
// It is considered a good practice to execute these lines once and
// cache the validator instances.
public static final ClassValidator<Customer> CUSTOMER_VALIDATOR =
new ClassValidator<Customer>(Customer.class);
public static final ClassValidator<CreditCard> CREDIT_CARD_VALIDATOR =
new ClassValidator<CreditCard>(CreditCard.class);
private static ClassValidator<? extends BaseObject> getValidator(Class<?
extends BaseObject> clazz) {
if (Customer.class.equals(clazz)) {
return CUSTOMER_VALIDATOR;
}
else if (CreditCard.class.equals(clazz)) {
return CREDIT_CARD_VALIDATOR;
}
else {
throw new IllegalArgumentException("Unsupported class was passed.");
}
}
public static InvalidValue[] getInvalidValues(BaseObject modelObject) {
String nullnullProperty = null;
return getInvalidValues(modelObject, nullProperty);
}
public static InvalidValue[] getInvalidValues(BaseObject modelObject,
String property) {
Class<? extends BaseObject>clazz = modelObject.getClass();
ClassValidator validator = getValidator(clazz);
InvalidValue[] validationMessages;
if (property == null) {
validationMessages = validator.getInvalidValues(modelObject);
}
else {
// only get invalid values for specified property.
// For example, "city" applies to getCity() method.
validationMessages = validator.getInvalidValues(modelObject, property);
}
return validationMessages;
}
} 创建了两个Hibernate ClassValidator，一个用于 Customer，另外一个用于 CreditCard。这两个希望进行验证的类可以调用 getInvalidValues(BaseObject modelObject)，会返回 InvalidValue[]。这则会返回一个包含模型对象实例错误的数组。另外，这个方法也可以通过提供一个特定的属性名来调用，这样做会只返回与该域有关的错误。
在使用 Spring MVC 和 Hibernate Validator 时，为信用卡创建一个验证过程变得非常简单，如下所示：
Spring MVC 控制器使用的 CreditCardValidator
/**
* Performs validation of a CreditCard in Spring MVC.
*
* @author Ted Bergeron
* @version $Id: CreditCardValidator.java,v 1.2 2006/02/10 21:53:50 ted Exp $
*/
public class CreditCardValidator implements Validator {
private CreditCardService creditCardService;
public void setCreditCardService(CreditCardService service) {
this.creditCardService = service;
}
public boolean supports(Class clazz) {
return CreditCard.class.isAssignableFrom(clazz);
}
public void validate(Object object, Errors errors) {
CreditCard creditCard = (CreditCard) object;
InvalidValue[] invalids = AnnotationValidator.getInvalidValues(creditCard);
// Perform "expensive" validation only if no simple errors found above.
if (invalids == null || invalids.length == 0) {
boolean validCard = creditCardService.validateCreditCard(creditCard);
if (!validCard) {
errors.reject("error.creditcard.invalid");
}
}
else {
for (InvalidValue invalidValue : invalids) {
errors.rejectValue(invalidValue.getPropertyPath(),
null, invalidValue.getMessage());
}
}
}
}