实现自定义校验注解，ConstraintValidator接口
/**
* Defines the logic to validate a given constraint {@code A}
* for a given object type {@code T}.
* <p>
* Implementations must comply to the following restriction:
* <ul>
* <li>{@code T} must resolve to a non parameterized type</li>
* <li>or generic parameters of {@code T} must be unbounded
* wildcard types</li>
* </ul>
* <p>
* The annotation {@link SupportedValidationTarget} can be put on a
* {@code ConstraintValidator} implementation to mark it as supporting
* cross-parameter constraints. Check out {@link SupportedValidationTarget}
* and {@link Constraint} for more information.
*
* @param <A> the annotation type handled by an implementation
* @param <T> the target type supported by an implementation
*
* @author Emmanuel Bernard
* @author Hardy Ferentschik
*/
public interface ConstraintValidator<A extends Annotation, T> {
/**
* Initializes the validator in preparation for
* {@link #isValid(Object, ConstraintValidatorContext)} calls.
* The constraint annotation for a given constraint declaration
* is passed.
* <p>
* This method is guaranteed to be called before any use of this instance for
* validation.
* <p>
* The default implementation is a no-op.
*
* @param constraintAnnotation annotation instance for a given constraint declaration
*/
default void initialize(A constraintAnnotation) {
}
/**
* Implements the validation logic.
* The state of {@code value} must not be altered.
* <p>
* This method can be accessed concurrently, thread-safety must be ensured
* by the implementation.
*
* @param value object to validate
* @param context context in which the constraint is evaluated
*
* @return {@code false} if {@code value} does not pass the constraint
*/
boolean isValid(T value, ConstraintValidatorContext context);
}
1.initialize方法
会在校验实例化后被调用，一般用于做些初始化工作。
2.isValid方法
实际执行验证的方法，第一个参数获取的是字段或对象实际对应的值，取决于类的枚举限定类型。第二个参数是ConstraintValidatorContext，上下文可以做些默认的设置。
本文使用自定义校验注解验证身份证是否符合要求。
@Constraint(validatedBy = IdCardValidator.class)
@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface IdCard {
String message() default "身份证不合法";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
public class IdCardValidator implements ConstraintValidator<IdCard, String> {
@Override
public void initialize(IdCard constraintAnnotation) {
}
@Override
public boolean isValid(String s, ConstraintValidatorContext constraintValidatorContext) {
return IdCardUtils.checkIdCard(s);
}
}
@IdCard
private String idCard;