Spring中返回String類型的算法怎么改成返回List類型？

Question

這個片段的工作是：當我以列表的形式給出一個長的唯一 url 時，它將它轉換為一個短的 url。

@Slf4j
@Service
public class ShortUrlService {
        private static final String SERVICE_URL = "http://mysite.co/example-api.php";
        private static final String SIGNATURE = "45abc12345";
        private static final String ACTION = "shorturl";
        private static final String FORMAT = "simple";
        private static final String SERVICE_CALL_FAIL = "SERVICE_CALL_FAIL";
        
        private Random random = new Random();
        
        @Autowired
        private HttpClient httpClient;
    
        public String shortenUrl(String url, String pCache) {
            String shortUrl = null;
            String longUrl = url;
            
            if (!StringUtils.isEmpty(pCache)) {
                longUrl = addCacheParameter(url, pCache);
            }
            
            longUrl = longUrl.replace("&", "%26");
            
            try {
                shortUrl = httpClient.getRequest(buildServiceUrl(longUrl));
            } catch (IOException e) {
                log.error("Service call failed: " + e.getMessage());
                shortUrl = SERVICE_CALL_FAIL;
            }
            
            log.info("Short URL: " + shortUrl);
            
            if (shortUrl.contains("-")) {
                int rand = random.nextInt(999999);
                return shortenUrl(url, String.valueOf(rand));
            }
            
            return shortUrl;
        }
        
        private String addCacheParameter(String url, String pCache) {
            if (url.contains("?")) {
                return url + "&pCache=" + pCache;
            } else {
                return url + "?pCache=" + pCache;
            }
        }
    
        private String buildServiceUrl(String url) {
            StringBuilder sb = new StringBuilder();
    
            sb.append(SERVICE_URL);
            sb.append("?signature=");
            sb.append(SIGNATURE);
            sb.append("&action=");
            sb.append(ACTION);
            sb.append("&url=");
            sb.append(url);
            sb.append("&format=");
            sb.append(FORMAT);
            
            log.info("Built URL: " + sb.toString());
            
            return sb.toString();
        }
        
}

我有如下服務。 這個服務的返回值就是我要改成的List。 我在這里的幾個地方都遇到了問題，你能幫我修復代碼嗎？

@Slf4j
@Service
public class ShortUrlService {
      private static final String SERVICE_URL = "http://mysite.co/example-api.php";
      private static final String SIGNATURE = "45abc12345";
      private static final String ACTION = "shorturl";
      private static final String FORMAT = "simple";
      private static final String SERVICE_CALL_FAIL = "SERVICE_CALL_FAIL";
                
      private Random random = new Random();
            
      @Override
      public List<String> shortenUrl(List<String> url, String pCache) {
          List<String> shortUrl = null;
          List<String> longUrl = url;
    
          if (!StringUtils.isEmpty(pCache)) {
              longUrl = Collections.singletonList(addCacheParameter(url, pCache));
          }
    
          **longUrl = longUrl.replace("&", "%26");**
    
    
          RestTemplate restTemplate = new RestTemplate();
    
            try {
                **shortUrl = restTemplate.getForObject(buildServiceUrl(longUrl),List.class);**
            } catch (Exception e) {
                log.error("Service call failed: " + e.getMessage());
                 **shortUrl =  SERVICE_CALL_FAIL;**
            }
    
            log.info("Short URL: " + shortUrl);
    
            if (shortUrl.contains("-")) {
                int rand = random.nextInt(999999);
                return shortenUrl(url, String.valueOf(rand));
            }
    
            return shortUrl;
        }
    
        private String addCacheParameter(List<String> url, String pCache) {
            if (url.contains("?")) {
                return url + "&pCache=" + pCache;
            } else {
                return url + "?pCache=" + pCache;
            }
        }
    
        private String buildServiceUrl(List<String> url) {
            StringBuilder sb = new StringBuilder();
    
            sb.append(SERVICE_URL);
            sb.append("?signature=");
            sb.append(SIGNATURE);
            sb.append("&action=");
            sb.append(ACTION);
            sb.append("&url=");
            sb.append(url);
            sb.append("&format=");
            sb.append(FORMAT);
    
            log.info("Built URL: " + sb.toString());
    
            return sb.toString();
        }
                
}

這里 httpClient.getRequest 拋出一個錯誤，因為它仍然是一項舊技術。 我想改用 RestTemplate。 但是我用對了嗎？ 我怎樣才能將替換方法寫成 replaceAll？

Answer 1

使用 for 循環，將List中的每個 URL 縮短，並將它們添加到另一個List以返回。

List<String> shortUrls = new ArrayList<>(urls.size());
if (!StringUtils.isEmpty(pCache)) {
  longUrl = Collections.singletonList(addCacheParameter(url, pCache));
}
RestTemplate restTemplate = new RestTemplate();
for (String url: urls) {
    String longUrl = url.replace("&", "%26");
    String shortUrl = null;
    try {
        shortUrl = restTemplate.getForObject(buildServiceUrl(longUrl),List.class);
    } catch (Exception e) {
        log.error("Service call failed: " + e.getMessage());
         shortUrl = SERVICE_CALL_FAIL;
    }
    log.info("Short URL: " + shortUrl);
    if (shortUrl.contains("-")) {
        int rand = random.nextInt(999999);
        shortUrl = shortenUrl(url, String.valueOf(rand));
    }
    shortUrls.add(shortUrl);
}
return shortUrls;

Answer 2

@Slf4j
@Service
public class ShortUrlService {
      private static final String SERVICE_URL = "http://mysite.co/example-api.php";
      private static final String SIGNATURE = "45abc12345";
      private static final String ACTION = "shorturl";
      private static final String FORMAT = "simple";
      private static final String SERVICE_CALL_FAIL = "SERVICE_CALL_FAIL";
                
      private Random random = new Random();
            
      @Override
      public List<String> shortenUrl(List<String> urls, String pCache, List<String> shortUrls, List<String> longUrls) {
          
          for(String url:urls){            
          if (!StringUtils.isEmpty(pCache)) {
              longUrl = Collections.singletonList(addCacheParameter(url, pCache));
              longUrl = longUrl.replace("&", "%26");
              longUrls.add(longUrl);
          }
          RestTemplate restTemplate = new RestTemplate();    
            try {
                **shortUrl = restTemplate.getForObject(buildServiceUrl(longUrl));**
            } catch (Exception e) {
                log.error("Service call failed: " + e.getMessage());
                 **shortUrl =  SERVICE_CALL_FAIL;**
            }
    
            log.info("Short URL: " + shortUrl);
    
            if (shortUrl.contains("-")) {
                int rand = random.nextInt(999999);
                return shortenUrl(url, String.valueOf(rand));
            }
            shortUrls.add(shortUrl);
            
           }
            return shortUrls;
        }
    
        private String addCacheParameter(String url, String pCache) {
            if (url.contains("?")) {
                return url + "&pCache=" + pCache;
            } else {
                return url + "?pCache=" + pCache;
            }
        }
    
         private String buildServiceUrl(String url) {
            StringBuilder sb = new StringBuilder();
    
            sb.append(SERVICE_URL);
            sb.append("?signature=");
            sb.append(SIGNATURE);
            sb.append("&action=");
            sb.append(ACTION);
            sb.append("&url=");
            sb.append(url);
            sb.append("&format=");
            sb.append(FORMAT);
            
            log.info("Built URL: " + sb.toString());
            
            return sb.toString();
        }
                
}

試試這個。修改了一些部分。

Answer 3

在過程語言中，如果你有一些東西適用於一件事，而你需要支持多件事，那么解決方案在 99% 的情況下都是一個循環。

如果您已經有一個方法來處理一件事，您可以創建一個重載並將實際工作委托給這個方法。 這會起作用，但可能並不總是最有效的解決方案（例如考慮 N+1 select 問題）。 有些事情最好在循環之前完成一次，而不是每次執行循環體時都完成。

對於您的問題，最簡單的方法是提供重載（或類似命名的方法）。 如果您不想再調用單參數方法，可以將其標記為私有。

啟用列表的方法實例化要返回的新列表，調用原始方法並將其結果添加到列表中。 列表最終返回：

    public List<String> shortenUrls(final List<String> urls, final String pCache) {
        final List<String> shortUrls = new ArrayList<>();
        for (final String url : urls) {
            shortUrls.add(shortenUrl(url, pCache));
        }
        return shortUrls;
    }

    public String shortenUrl(String url, String pCache) {
        // nothing to change in this method, except maybe make it `private`
        String shortUrl = null;
        String longUrl = url;
        
        if (!StringUtils.isEmpty(pCache)) {
            longUrl = addCacheParameter(url, pCache);
        }
        
        longUrl = longUrl.replace("&", "%26");
        
        try {
            shortUrl = httpClient.getRequest(buildServiceUrl(longUrl));
        } catch (IOException e) {
            log.error("Service call failed: " + e.getMessage());
            shortUrl = SERVICE_CALL_FAIL;
        }
        
        log.info("Short URL: " + shortUrl);
        
        if (shortUrl.contains("-")) {
            int rand = random.nextInt(999999);
            return shortenUrl(url, String.valueOf(rand));
        }
        
        return shortUrl;
    }