Question

在编写了几个后端API后，我发现以下代码几乎在每个需要按日期过滤数据的方法中都重复：

@GetMapping(value="/api/test")
@ResponseBody
public Result test(@RequestParam(value = "since", required = false) @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate since,
                   @RequestParam(value = "until", required = false) @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate until) {
    // Date validation code I want to eliminate
    since = ObjectUtils.defaultIfNull(since, DEFAULT_SINCE_DATE);
    until = ObjectUtils.defaultIfNull(until, LocalDate.now().plusDays(1));
    if(since.isAfter(until)) {
        throw new SinceDateAfterUntilDateException();
    }

    // Do stuff
}

显然这是某种代码味道。但是，因为我确实需要在使用它们来查询服务/ DAO之前验证since和until，我不知道应该在哪里提取这些代码？

有什么建议吗？

Answer 1

实施org.springframework.core.convert.converter.Converter;接口
注册弹簧转换服务。
在控制器中使用分享以下示例代码：

public class MyCustomDateTypeConverter implements Converter<String, LocalDate> {

  @Override
  public LocalDate convert(String param) {
      //convert string to DateTime
      return dateTiemObjectCreatedfromParam;
  }

}

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">  <property name="converters">    <list>
        <bean class="com.x.y.z.web.converters.MyCustomDateTypeConverter"/>  </list>     </property> 
</bean>


<mvc:annotation-driven conversion-service="conversionService">

</mvc:annotation-driven>


public Result test(LocalDate since,LocalDate until) {

    since = ObjectUtils.defaultIfNull(since, DEFAULT_SINCE_DATE);
    until = ObjectUtils.defaultIfNull(until, LocalDate.now().plusDays(1));
    if(since.isAfter(until)) {
        throw new SinceDateAfterUntilDateException();
    }

    // Do stuff
}

Answer 2

正如ol'gud-procedural方法所暗示的那样：

public Result test(@RequestParam(value = "since", required = false) @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate since,
               @RequestParam(value = "until", required = false) @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate until) {
     checkInputDates();
     // Do stuff
}

private checkInputDates(LocalDate since, LocalDate until) {
    since = ObjectUtils.defaultIfNull(since, DEFAULT_SINCE_DATE);
    until = ObjectUtils.defaultIfNull(until, LocalDate.now().plusDays(1));
    if(since.isAfter(until)) {
        throw new SinceDateAfterUntilDateException();
    }
}
//so on..

Answer 3

如果您有从对象收到的请求参数，那么您可以通过使用Bean级别验证（JSR 303）和自定义日期反序列化器来扩展Jackson序列化程序。这样你就没有检查params为null。

{{1}}

Answer 4

我建议使用自定义 bean validation 保存参数 since 和 until 的模型类型（使用 Lombok，但您也可以编写 getter 和 setter）。默认值现在是字段初始值设定项：

@Ordered({"since", "until"})
@Data
public class DateRange {
  @NotNull
  @PastOrPresent
  private LocalDate since = DEFAULT_SINCE_DATE;
  @NotNull
  private LocalDate until = LocalDate.now().plusDays(1);
}

@GetMapping(value="/api/test")
@ResponseBody
public Result test(@Valid DateRange dateFilter) {
    // Do stuff
}

要进行验证，您需要自定义 bean 验证约束：

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Constraint(validatedBy = OrderedValidator.class)
public @interface Ordered {
    /** The property names with comparable values in the expected order. **/
    String[] value();

    String message() default "{com.stackoverflow.validation.Ordered.message}";

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

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

以及检查约束的验证器（抱歉，小泛型让它适用于任何类型的 Comparable 值，而不是仅适用于 LocaleDate）：

public class OrderedValidator implements ConstraintValidator<Ordered, Object>
{
    private String[] properties;

    @Override
    public void initialize(Ordered constraintAnnotation) {
        if (constraintAnnotation.value().length < 2) {
            throw new IllegalArgumentException("at least two properties needed to define an order");
        }
        properties = constraintAnnotation.value();
    }

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {
        return isValid(value));
    }

    private <T extends Comparable<? super T>> boolean isValid(Object value)
    {
        List<T> values = getProperties(value);
        return isSorted(values);
    }

    private <T extends Comparable<? super T>> List<T> getProperties(Object value)
    {
        BeanWrapperImpl bean = new BeanWrapperImpl(value);
        return Stream.of(properties)
            .map(bean::getPropertyDescriptor)
            .map(pd -> this.<T>getProperty(pd, value))
            .filter(Objects::nonNull)
            .collect(Collectors.toList());
    }

    // See https://stackoverflow.com/a/3047160/12890
    private <T extends Comparable<? super T>> boolean isSorted(Iterable<T> iterable) {
        Iterator<T> iter = iterable.iterator();
        if (!iter.hasNext()) {
            return true;
        }
        T t = iter.next();
        while (iter.hasNext()) {
            T t2 = iter.next();
            if (t.compareTo(t2) > 0) {
                return false;
            }
            t = t2;
        }
        return true;
    }

    @SuppressWarnings("unchecked")
    private <T extends Comparable<? super T>> T getProperty(PropertyDescriptor prop, Object bean) {
        try {
            return prop.getReadMethod() == null ? null : (T)prop.getReadMethod().invoke(bean);
        } catch (ReflectiveOperationException noAccess) {
            return null;
        }
    }
}

在Spring控制器中使用日期参数的最佳实践？

4 个答案: