Docker: Can't read class path resource from spring boot application

Question

Reading a classpath resource as,

    try {
        final ClassPathResource classPathResource = new ClassPathResource(format("location%sGeoLite2-City.mmdb", File.separator));
        final File database = classPathResource.getFile();
        dbReader = new DatabaseReader.Builder(database).build();
    } catch (Exception e) {
        System.out.println("Exception: " + e);
    }

I've packaged this with docker using following Dockerfile,

FROM java:8
ADD build/libs/*.jar App.jar
CMD java -jar App.jar

But while running this application as docker run -p 8080:8080 app-image I can hit the application endpoint and from application logs I can see it fails to read this file (following is from logs),

Exception: java.io.FileNotFoundException: class path resource [location/GeoLite2-City.mmdb] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/App.jar!/BOOT-INF/classes!/location/GeoLite2-City.mmdb

Would appreciate any comment, Things to know before you comment,

**- Running on windows 10, intellij 2018.2, jdk 8
- Can run application successfully with intellij as well as command line - File exists in jar (I did extract jar and checked ) **

Answer 1

Since you are using springboot you can try to use the following annotation for loading your classpath resource. Worked for me because I had the same exception. Be aware that the directory "location" must be under the src/main/resources folder:

@Value("classpath:/location/GeoLite2-City.mmdb")
private Resource geoLiteCity;

Without springboot you could try:

try (InputStream inputStream = getClass().getClassLoader().getResourceAsStream("/location/GeoLite2-City.mmdb")) {
... //convert to file and other stuff
}

Also the answers before were correct as the use of "/" is not good at all and File.separator would be the best choice.

Answer 2

It is not a good approach to use slashes.

Always use File Seperators as they work irrespective of System OS.

Change

(location\\GeoLite2-City.mmdb)

to

("location"+ File.separator +"GeoLite2-City.mmdb")

Refer this for more.

https://www.journaldev.com/851/java-file-separator-separatorchar-pathseparator-pathseparatorchar

Difference between File.separator and slash in paths