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。

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.");

}

}

}

}

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