如何写出一个jsr-303 参数校验注解

例如我们写一个验证手机号的注解:

@Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER})
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {IsMobileValidator.class})
public @interface IsMobile {

    /**
     * 参数默认为true
     *
     * @return
     */
    boolean required() default true;

    /**
     * 校验不通过提示
     * @return
     */
    String message() default "手机号码格式错误";

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

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

编写验证器：

public class IsMobileValidator implements ConstraintValidator<IsMobile, String> {

    private boolean required = false;

    @Override
    public void initialize(IsMobile constraintAnnotation) {
        required = constraintAnnotation.required();
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if (required) {
            return ValidatorUtil.isMobile(value);
        } else {
            if (StringUtils.isEmpty(value)) {
                return true;
            } else {
                return ValidatorUtil.isMobile(value);
            }
        }
    }

}

public class ValidatorUtil {
	
	private static final Pattern mobile_pattern = Pattern.compile("1\\d{10}");
	
	public static boolean isMobile(String src) {
		if(StringUtils.isEmpty(src)) {
			return false;
		}
		Matcher m = mobile_pattern.matcher(src);
		return m.matches();
	}
}

把注解写在需要验证的参数上方即可：

public class LoginVo {
	
	@NotNull
	@IsMobile
	private String mobile;
}