Refactoring code that contains multiple if conditions

Here is some code I've written to save a UrlEntity :

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);
            }
        }
    }
}

The above code exists in a service class and looks unnecessarily complex. I'm attempting to refactor so that the intent is clear. This is a basic refactoring I've written:

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);
    }
}

This refactoring does not improve the code substantially. Is there a code pattern or idiomatic way to refactor the method saveUrlEntity? I'm using Java11

This is very subjective, but... Since most of your if statements are guard/short-circuit clauses, which throw or return, there is no need to use else. I think this simple change makes the code much more readable.

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);
}

I'd also recommend replacing urlEntity.size() > 0 with !urlEntity.isEmpty().

The method does seem to be doing several things, which violates the Single Responsibility Principle; you might want to think about breaking that out better.

If you use throw new or return you do not need the else condition because the method ends like

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);
}