java - 如何强制 spring org.springframework.format.annotation.DateTimeFormat 为自定义 DateFormatter

Question

我有一个场景，我有不同类型的日期即将到来，在这种情况下，现有的 spring 转换会失败，因为即将到来的日期格式不同。

有没有办法让 Spring 使用我的自定义 DateFormatter ？

Answer 1

Is there a way I can make Spring use my custom DateFormatter ?

是的，但由于您的用例是特定的，我认为最好使用自定义注释来使所有内容明确。

这些interface s 可用于完成此任务:

• Formatter
• AnnotationFormatterFactory

这些类的源码可以作为引用:

• Jsr310DateTimeFormatAnnotationFormatterFactory
• DateTimeFormatAnnotationFormatterFactory
• NumberFormatAnnotationFormatterFactory

你可以这样做:

UnstableDateFormats注释

@Retention(RUNTIME)
public @interface UnstableDateFormats {
  String[] formatsToTry();
}

Formatter实现

public class UnstableDateFormatter implements Formatter<LocalDate> {
  private final List<String> formatsToTry;

  public UnstableDateFormatter(List<String> formatsToTry) {
    this.formatsToTry = formatsToTry;
  }

  @Override
  public LocalDate parse(String text, Locale locale) throws ParseException {
    for (String format : formatsToTry) {
      try {
        return LocalDate.parse(text, DateTimeFormatter.ofPattern(format));
      } catch (DateTimeParseException ignore) {
        // or log the exception
      }
    }
    throw new IllegalArgumentException("Unable to parse \"" + text
        + "\" as LocalDate using formats = " + String.join(", ", formatsToTry));
  }

  @Override
  public String print(LocalDate object, Locale locale) {
    // Implement this method thoroughly
    // If you're accepting dates in different formats which one should be used to print the value?
    return object.toString();
  }
}

AnnotationFormatterFactory实现

public class UnstableDateFormatAnnotationFormatterFactory implements AnnotationFormatterFactory<UnstableDateFormats> {
  @Override
  public Set<Class<?>> getFieldTypes() {
    return Collections.singleton(LocalDate.class);
  }

  @Override
  public Printer<?> getPrinter(UnstableDateFormats annotation, Class<?> fieldType) {
    return new UnstableDateFormatter(Arrays.asList(annotation.formatsToTry()));
  }

  @Override
  public Parser<?> getParser(UnstableDateFormats annotation, Class<?> fieldType) {
    return new UnstableDateFormatter(Arrays.asList(annotation.formatsToTry()));
  }
}

不要忘记注册 AnnotationFormatterFactory实现:

如果您使用 spring mvc，您可以在 Web 配置中执行此操作(请参阅 Type Conversion ):

public class MvcConfig implements WebMvcConfigurer {
  @Override
  public void addFormatters(FormatterRegistry registry) {
    registry.addFormatterForFieldAnnotation(new UnstableDateFormatAnnotationFormatterFactory());
  }
}

另请参阅:

• Spring Field Formatting

您可能还需要考虑:

• Configuring a Global Date and Time Format