資源加載器

使用Java，您可以使用當前線程的classLoader并嘗試加載文件，但是Spring Framework為您提供了更為優雅的解決方案，例如ResourceLoader。

您只需要自動連接ResourceLoader，然后調用getResource(„somePath“)方法即可。

在Spring Boot（WAR）中從資源目錄/類路徑加載文件的示例

在以下示例中，我們從類路徑中加載名為GeoLite2-Country.mmdb的文件作為資源，然后將其作為File對象檢索。

@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/類路徑加載文件的示例

如果您想從Spring Boot JAR中的 classpath加載文件，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，則會收到錯誤消息，因為Spring嘗試訪問文件系統路徑，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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