java自定义验证器的实现示例

        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
        </dependency>

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;

/**
 * 银行卡号校验注解
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
// 这里指定验证器
@Constraint(validatedBy = {BankCardValidator.class})
@Target({ElementType.FIELD,ElementType.ANNOTATION_TYPE,ElementType.PARAMETER})
public @interface BankCardValidity {

    /**
     * 提示信息
     * @return String
     */
    String message() default "";

    /**
     * 是否验证
     * @return boolean
     */
    boolean required() default true;

    /**
     * groups
     * @return []
     */
    Class<?>[] groups() default {};


    /**
     * payload
     * @return []
     */
    Class<? extends Payload>[] payload() default {};
}

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * 银行卡号校验器
 */
public class BankCardValidator implements ConstraintValidator<BankCardValidity,String> {

    /**
     * 是否强制验证
     */
    private boolean required = false;

    /**
     * 银行卡号正则校验,这里就是一个正则验证
     */
    private static Pattern patternForBankCardNo = Pattern.compile("^([1-9]{1})(\\d{15}|\\d{18})$");
	
	/**
	 * 这里就是验证逻辑，返回true验证通过，返回false验证不通过
	 */
    @Override
    public boolean isValid(String bankCardNo, ConstraintValidatorContext context) {
        if (required) {
            return isBankCardNo(bankCardNo);
        } else {
            if (StrUtil.isBlank(bankCardNo)) {
                return false;
            }
            return isBankCardNo(bankCardNo);
        }
    }

    @Override
    public void initialize(BankCardValidity validity) {
        required = validity.required();
    }

    /**
     * 验证是否为银行卡号
     * @param bankCardNo 输入内容
     * @return boolean
     */
    private static boolean isBankCardNo(String bankCardNo) {
        // 使用的hutool工具包，也可以使用其它工具包
        if (StrUtil.isBlank(bankCardNo)) {
            return false;
        }
        Matcher matcherForBankCardNo = patternForBankCardNo.matcher(bankCardNo);
        return matcherForBankCardNo.matches() ;
    }
}