在Spring Boot中从类路径加载文件的示例

资源加载器

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Spring Boot（WAR）中从资源目录/类路径加载文件的示例

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.");
      }
    }
  }
} 

在Spring Boot（JAR）中从资源目录/类路径加载文件的示例

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.");
      }
    }
  }
} 

以上就是在Spring Boot中从类路径加载文件的示例的详细内容，更多关于spring boot 加载文件的资料请关注我们其它相关文章！