在Spring Boot中从类路径加载文件

介绍

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WARJAR中加载文件的解决方案

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.");
            }
        }
    }
}

 

 
posted @ 2020-03-26 23:32  纵码万水千山  阅读(1043)  评论(0编辑  收藏  举报