資源載入器

使用Java，您可以使用當前執行緒的classLoader並嘗試載入檔案，但是Spring Framework為您提供了更為優雅的解決方案，例如ResourceLoader。

您只需要自動連線ResourceLoader，然後呼叫getResource(„somePath“)方法即可。

在Spring Boot（WAR）中從資源目錄/類路徑載入檔案的示例

在以下示例中，我們從類路徑中載入名為GeoLite2-Country.mmdb的檔案作為資源，然後將其作為File物件檢索。

@Service("geolocationservice") 
public class GeoLocationServiceImpl implements GeoLocationService { 
 private static final Logger LOGGER = LoggerFactory.getLogger(GeoLocationServiceImpl.class); 
 private static DatabaseReader reader = null; 
 private ResourceLoader resourceLoader; 
 @Autowired 
 public GeoLocationServiceImpl(ResourceLoader resourceLoader) { 
  this.resourceLoader = resourceLoader; 
 } @PostConstruct 
 public void init() { 
  try { 
   LOGGER.info("GeoLocationServiceImpl: Trying to load GeoLite2-Country database..."); 
   Resource resource = resourceLoader.getResource("classpath:GeoLite2-Country.mmdb"); 
   File dbAsFile = resource.getFile();   // Initialize the reader 
   reader = new DatabaseReader 
      .Builder(dbAsFile) 
      .fileMode(Reader.FileMode.MEMORY) 
      .build(); 
   LOGGER.info("GeoLocationServiceImpl: Database was loaded successfully."); 
  } catch (IOException | NullPointerException e) { 
   LOGGER.error("Database reader cound not be initialized. ",e); 
  } 
 } 
 @PreDestroy 
 public void preDestroy() { 
  if (reader != null) { 
   try { 
    reader.close(); 
   } catch (IOException e) { 
    LOGGER.error("Failed to close the reader."); 
   } 
  } 
 } 
} 

在Spring Boot（JAR）中從資源目錄/類路徑載入檔案的示例

如果您想從Spring Boot JAR中的 classpath載入檔案，則必須使用該resource.getInputStream()方法將其作為InputStream檢索。如果嘗試使用resource.getFile()該方法，則會收到錯誤訊息，因為Spring嘗試訪問檔案系統路徑，但無法訪問JAR中的路徑。

@Service("geolocationservice") 
public class GeoLocationServiceImpl implements GeoLocationService { 
 private static final Logger LOGGER = LoggerFactory.getLogger(GeoLocationServiceImpl.class); 
 private static DatabaseReader reader = null; 
 private ResourceLoader resourceLoader; 
 @Inject 
 public GeoLocationServiceImpl(ResourceLoader resourceLoader) { 
  this.resourceLoader = resourceLoader; 
 } @PostConstruct 
 public void init() { 
  try { 
   LOGGER.info("GeoLocationServiceImpl: Trying to load GeoLite2-Country database..."); 
   Resource resource = resourceLoader.getResource("classpath:GeoLite2-Country.mmdb"); 
   InputStream dbAsStream = resource.getInputStream(); // <-- this is the difference 
   // Initialize the reader 
   reader = new DatabaseReader 
      .Builder(dbAsStream) 
      .fileMode(Reader.FileMode.MEMORY) 
      .build(); 
   LOGGER.info("GeoLocationServiceImpl: Database was loaded successfully."); 
  } catch (IOException | NullPointerException e) { 
   LOGGER.error("Database reader cound not be initialized. ",e); 
  } 
 } 
 @PreDestroy 
 public void preDestroy() { 
  if (reader != null) { 
   try { 
    reader.close(); 
   } catch (IOException e) { 
    LOGGER.error("Failed to close the reader."); 
   } 
  } 
 } 
} 

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