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.");
}
}
}
}
