创建Spring Boot Web应用程序时，有时有时需要从类路径中加载文件；war和jar的加载文件格式是不一样的
在下面，您将找到在WAR和JAR中加载文件的解决方案。
使用Java，您可以使用当前线程的classLoader并尝试加载文件，但是Spring Framework为您提供了更为优雅的解决方案，例如ResourceLoader。
您只需要自动连接ResourceLoader，然后调用getResource(„somePath“)方法即可。
在以下示例中，我们从类路径中加载名为GeoLite2-Country.mmdb的文件作为资源，然后将其作为File对象检索。
@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."); } } } }
如果您想从Spring Boot JAR中的 classpath加载文件，则必须使用该resource.getInputStream()方法将其作为InputStream检索。如果尝试使用resource.getFile()该方法，则会收到错误消息，因为Spring尝试访问文件系统路径，但无法访问JAR中的路径。
@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."); } } } }
原文：https://www.cnblogs.com/guanbin-529/p/12578411.html