参考：
https://docs.jboss.org/hibernate/validator/4.3/reference/zh-CN/html/validator-customconstraints.html#validator-customconstraints-errormessage
https://www.ibm.com/developerworks/cn/java/j-lo-beanvalid/index.html
https://blog.csdn.net/qq920447939/article/details/80198438

 入参的校验很多啊，不能为空，必须为手机号，必须为中文等等等等。下面是归类。

一 已有的参数校验规则

在你的dto上直接用注解定义校验规则，都是些常见的实用的规则

@Getter
@Setter
public class FormContent implements Serializable {

    @NotNull(message = "serialNo必须有值")
    String serialNo;

    @NotBlank(message = "id不能为空")
    String id;

    @Email(message = "email不是一个合法的电子邮件地址|为空时不会判定")
    String email;

    @NotBlank(message = "手机号不能为空")
    @Pattern(regexp = "^(1)\\d{10}$", message = "请输入正确的手机号")
    String mobile;

    @NotBlank(message = "身份证号码不能为空")
    @Pattern(regexp = "^(\\d{15}$)|(^\\d{18}$)|(^\\d{17}(\\d|X|x)$)", message = "请输入正确的身份证号码")
    String idCardNo;

    @Pattern(regexp = "^[\\u4E00-\\u9FA5\\uf900-\\ufa2d·s]+$", message = "姓名只支持：中文和符号·")
    @Length(min = 1, max = 20, message = "姓名长度不符合规范")
    @NotBlank(message = "姓名不能为空")
    String name;

    @AssertTrue(message = "agree只能为true")
    boolean agree;

    //级联验证
    @Valid
    @NotNull(message = "地址不能为空")
    Address address;

    @DecimalMin(value = "0.00", message = "金额必须大于0")
    @DecimalMax(value = "10000.00", message = "金额必须小于10000")
    String amount;

    @Size(min = 1, max = 5, message = "爱好大于1个，小于5个")
    final List<String> hobbies = new ArrayList<>();

    @Future(message = "expireTime is not less than now")
    Date expireTime;
}

@Builder
@Getter
@Setter
public class Address {

    @NotBlank(message = "省为空")
    String province;

    @NotBlank(message = "市为空")
    String city;

    @NotBlank(message = "区为空")
    String region;

    @Length(min = 1, max = 50, message = "详细地址长度不符合规范")
    @NotBlank(message = "详细地址为空")
    String address;
}

具体校验工具（可以写在切面，统一校验就完事了）

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.groups.Default;
import java.util.Set;

public class ValidateCheckUtils {

    private static Validator validator;

    public static <T> void check(T obj) {
        if (validator == null) {
            validator = Validation.buildDefaultValidatorFactory().getValidator();
        }
        Set<ConstraintViolation<T>> set = validator.validate(obj, Default.class);
        if (set != null && set.size() > 0) {
            String property = null;
            for (ConstraintViolation<T> cv : set) {
                //这里循环获取错误信息，可以自定义格式
                property = cv.getMessage();
                throw new IllegalArgumentException(property);
            }
        }
    }
}

二 你也可以自定义校验规则

比如要校验字符串类型的日期，满足yyyy-MM-dd之类的格式。
首先，定义一个注解

@Target( { METHOD, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = CheckDateValidator.class)
@Documented
public @interface CheckDate {

    String message() default "日期不合规范";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    String format() default "yyyy-MM-dd";

}

然后定义具体的校验方法

public class CheckDateValidator implements ConstraintValidator<CheckDate, String> {

    private String format;

    public void initialize(CheckDate constraintAnnotation) {
        this.format = constraintAnnotation.format();
    }

    public boolean isValid(String object, ConstraintValidatorContext constraintContext) {

        if (object == null)
            return true;
        String pattern = format;
        boolean isValid = true;
        SimpleDateFormat format = new SimpleDateFormat(pattern);
        try {
            // 设置lenient为false. 否则SimpleDateFormat会比较宽松地验证日期，比如2007/02/29会被接受，并转换成2007/03/01
            format.setLenient(false);
            format.parse(object);
        } catch (Exception ex) {
            isValid = false;
        }
        return isValid;
    }
}

具体调用

    public static void main(String[] args) {
        FormContent formContent = new FormContent();
        formContent.setSerialNo("");
        formContent.setId("123");
        formContent.setEmail("");
        formContent.setMobile("15012345678");
        formContent.setIdCardNo("123456789012345");
        formContent.setAgree(true);
        formContent.setName("张三·买买提");

        Address address = Address.builder()
                .province("重庆市")
                .region("市辖区")
                .city("渝中区")
                .address("解放碑").build();
        formContent.setAddress(address);
        formContent.setAmount("1000.00");
        formContent.getHobbies().add("xixixi");
        formContent.getHobbies().add("hahaha");


        Calendar calendar = Calendar.getInstance();
        calendar.set(2020, 10, 1);
        Date date = calendar.getTime();

        formContent.setExpireTime(date);

        formContent.setLowerCase("asdasd");

        formContent.setCreateTime("2019-09-11");
        ValidateCheckUtils.check(formContent);
    }

完事~