重构包含多个 if 条件的代码

Question

这是我为保存 UrlEntity 编写的一些代码：

public UrlEntity saveUrlEntity(String longUrl, LocalDate dateAdded) {

    int urlLength = longUrl.length();
    if (urlLength >= Constants.MAX_LONG_URL_LENGTH) {
        throw new LongUrlLengthExceededException("URL with length " + urlLength + " exceeds the max length of " + Constants.MAX_LONG_URL_LENGTH + " characters");
    } else {

        List<UrlEntity> urlEntity = urlRepository.findByLongUrl(longUrl);
        if (urlEntity.size() > 0) {
            return urlEntity.get(0);
        } else {
            final String shortUrl = urlShorten.shortenURL(longUrl);
            if (urlRepository.findFirstByShortUrl(shortUrl).isPresent()) {
                logger.error("A short short URL collision occured for long URL: " + longUrl + " with generated short URL" + shortUrl);
                throw new ShortUrlCollisionException("A short URL collision occured");
            } else {
                logger.info("Shortened URL: " + shortUrl);

                final UrlEntity urlEntityToSave = new UrlEntity(dateAdded, longUrl, shortUrl);

                return urlRepository.save(urlEntityToSave);
            }
        }
    }
}

以上代码存在于服务 class 中，看起来过于复杂。我正在尝试重构以便意图明确。这是我写的基本重构：

public UrlEntity saveUrlEntity(String longUrl, LocalDate dateAdded) {

    int urlLength = longUrl.length();
    if (urlLength >= Constants.MAX_LONG_URL_LENGTH) {
        throw new LongUrlLengthExceededException("URL with length " + urlLength + " exceeds the max length of " + Constants.MAX_LONG_URL_LENGTH + " characters");
    } else {
        List<UrlEntity> urlEntity = urlRepository.findByLongUrl(longUrl);
        if (urlEntity.size() > 0) {
            return urlEntity.get(0);
        } else {
            return saveUrlEntityValue(longUrl, dateAdded);
        }
    }
}

private UrlEntity saveUrlEntityValue(String longUrl, LocalDate dateAdded){
    final String shortUrl = urlShorten.shortenURL(longUrl);
    if (urlRepository.findFirstByShortUrl(shortUrl).isPresent()) {
        logger.error("A short short URL collision occured for long URL: " + longUrl + " with generated short URL" + shortUrl);
        throw new ShortUrlCollisionException("A short URL collision occured");
    } else {
        logger.info("Shortened URL: " + shortUrl);

        final UrlEntity urlEntityToSave = new UrlEntity(dateAdded, longUrl, shortUrl);

        return urlRepository.save(urlEntityToSave);
    }
}

这种重构并没有显着改进代码。是否有重构方法 saveUrlEntity 的代码模式或惯用方式？我正在使用 Java11

Answer 1

如果您使用 throw new 或 return，则不需要 else 条件，因为该方法的结尾类似于

public UrlEntity saveUrlEntity(String longUrl, LocalDate dateAdded) {

    int urlLength = longUrl.length();
    if (urlLength >= Constants.MAX_LONG_URL_LENGTH) {
        throw new LongUrlLengthExceededException("URL with length " + urlLength + " exceeds the max length of " + Constants.MAX_LONG_URL_LENGTH + " characters");
    }
    
    List<UrlEntity> urlEntity = urlRepository.findByLongUrl(longUrl);
    if (urlEntity.size() > 0) {
        return urlEntity.get(0);
    }
    
    final String shortUrl = urlShorten.shortenURL(longUrl);
    if (urlRepository.findFirstByShortUrl(shortUrl).isPresent()) {
        logger.error("A short short URL collision occured for long URL: " + longUrl + " with generated short URL" + shortUrl);
        throw new ShortUrlCollisionException("A short URL collision occured");
    }
    
    logger.info("Shortened URL: " + shortUrl);
    final UrlEntity urlEntityToSave = new UrlEntity(dateAdded, longUrl, shortUrl);
    return urlRepository.save(urlEntityToSave);
}

Answer 2

这是非常主观的，但是...由于您的大多数 if 语句都是 guard/short-circuit 从句，即 throw 或 return，因此没有必要使用 else。我认为这个简单的更改使代码更具可读性。

public UrlEntity saveUrlEntity(String longUrl, LocalDate dateAdded) {

    final int urlLength = longUrl.length();
    if (urlLength >= Constants.MAX_LONG_URL_LENGTH) {
        throw new LongUrlLengthExceededException("URL with length " + urlLength + " exceeds the max length of " + Constants.MAX_LONG_URL_LENGTH + " characters");
    }

    final List<UrlEntity> urlEntity = urlRepository.findByLongUrl(longUrl);
    if (urlEntity.size() > 0) {
        return urlEntity.get(0);
    }

    final String shortUrl = urlShorten.shortenURL(longUrl);
    if (urlRepository.findFirstByShortUrl(shortUrl).isPresent()) {
        logger.error("A short short URL collision occured for long URL: " + longUrl + " with generated short URL" + shortUrl);
        throw new ShortUrlCollisionException("A short URL collision occured");
    }

    logger.info("Shortened URL: " + shortUrl);
    final UrlEntity urlEntityToSave = new UrlEntity(dateAdded, longUrl, shortUrl);
    return urlRepository.save(urlEntityToSave);
}

我还建议将 urlEntity.size() > 0 替换为 !urlEntity.isEmpty()。

该方法似乎确实在做几件事，这违反了单一职责原则；你可能想考虑更好地打破它。

重构包含多个 if 条件的代码

Refactoring code that contains multiple if conditions

java

refactoring

spring

design-patterns

spring-boot