How can I get the Url of file that is outside the jar?

I have deployed spring boot app in exploded mode using maven-assembly-plugin. I have made config folder from project’s resource folder.

The problem is that I am not able to get the url to access the file that is in the config folder.

How can I get the url of the file that I have uploaded and stored at this config folder.

File structure

Target folder:

+springdemo-0.0.1-application.zip
   +config
     +myfolder
        -oldfile.png
   +springdemo-0.0.1.jar	//running this jar file
   +start.sh
-springdemo-0.0.1.jar	

I want URL of files stored in myfolder. This url will be accessed by 3rd party(for ex. Picasso) to get file data. I am unable to get correct url pointing to this myfolder files.

Note: Not a SpringBoot-specific answer, just the simple Java way.

You can only try to guess the location of the file because there's no way to know the working directory when a Java application is run.

For example, you could try a very simple approach if you control how the Java application is executed:

var configFile = new File("config/application.properties");

This will works as long as the process is started from the same directory where start.sh is (which seems like what you intend).

If it doesn't work, try printing the working directory like this first:

System.out.println("WRK DIR = " + new File(".").getAbsolutePath());

This will tell you what the relative path to your file should be.
So, if this prints <root-dir>/springdemo and you know your config file is under <root-dir>/springdemo/mydir/config/, then the file path should be:

new File("mydir/config/application.properties");

By the way, you can easily read the file with:

// read file into List of lines
Files.readAllLines(configFile);

// specifically, for properties file
var props = new Properties();
props.load(new FileInputStream(configFile));

If for whatever reason you need an URL object instead of a File, it's easy, just call:

URL url = configFile.toURI().toURL()

If you want ALL files under the config dir, you can list them first with:

File[] files = configFile.getParentFile().listFiles();
if (files != null) {
    for (File file : files) {
        // use file?
    }
}

Its easy, you need to provide the full path of the external application.properties file than what is present in your source code during the startup of the spring-boot.jar application at runtime.

Example: java -jar -Dspring.config.location=file://<<full file path with name>>

This external file takes precedence over the one in our jar file.