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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.

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://<>
This external file takes precedence over the one in our jar file.

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?
}
}

File only accessible when placed in a location where it will be erased from the jar

I'm new to NetBeans IDE, and am struggling with accessing a file after building the jar file. After reading through many posts on this topic, I decided to try the following code:
BufferedReader read = new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/file.txt")));
This works fine when my file is placed inside the "build" folder of the project where the .class files are, but of course this is a problem because it is erased in the "clean and build" process when the jar file is created. I have tried placing it in the src folder, in a separate "resources" package, and in the root of directory. I have also tried calling getResourceAsStream() with "file.txt" and "/src/file.txt," but it only works in the above configuration when the file is with the .class files. Any tips would be much appreciated!

Why not have your file folder inside the tomcat bin and refer the directory from your code. So maven clean will not alter the files and you can remove, update file without needing to restart the application. ( here i have file inside etc )
Path: /Users/username/Documents/apache-tomcat-8.5.15/bin/etc
ArrayList<String> readList = null;
String workingDir = System.getProperty("user.dir");
String fileName = "File.txt";
File file = new File(workingDir+"/etc/" + fileName);
readList = resourceReader.readFile(file.getAbsolutePath());
I have method readFile to parse some data and build the ArrayList in the above example.
Read about System Properties

Turns out the solution was really simple...I had been trying to manually create a resources folder, but the contents kept being deleted upon building of the jar. Instead, I created a resources package and put the file into the auto-generated folder inside the src folder, which packaged the file into the jar. Thanks everyone!

How do I get the relative path of files in my project?

I am creating a project using jsp/servlet in which I am trying to create java file and class file inside the project itself. But I am able to do this for only my system because the path I give their is like : C:\Users\MySystem\Desktop\Test\.. which works only for my system. What should I do so that if I have to run this project in another system I don't have to change path again and again.

Well if it is maven project just put your resources files under src/main/resources
and you can read them using this lines.
String path = Thread.currentThread().getContextClassLoader()
.getResource("yourFileName").getPath();
System.out.println(path);
Or even this way you can do it.
String pathOfTheFile = getServletContext().getResource("yourFile").getPath();
and don't forget to put the file under web-content or webapp folder

ClassName.class.getResourceAsStream returning Null

I migrated project from Eclipse to Android Studio.
App compiles fine, but it has a crash related to nekohtml library.
Inside HTMLEntities class
//filename = "res/HTMLlat1.properties"
final InputStream stream = HTMLEntities.class.getResourceAsStream(filename);
stream is always null. I tried to move file to the same folder as class and gave full path like this
filename = "/org/cyberneko/html/res/HTMLlat1.properties"
Any ideas?

You should use filename = "/org/cyberneko/html/res/HTMLlat1.properties" instead of filename = "/org.cyberneko.html/res/HTMLlat1.properties" or use relative paths. This could be explained in this way: jar (jar is an example, maybe you're running your code from *.class in some directory) is just some kind of file system with it's root ("/") and all the files in the packages are in some subdirectories and you should specify the paths for them.

File path is working in NetBeans but not in built JAR file

I have a file holding default information that I use to load the textFields of my application. I looked up how to get this built into my jar file when I build and I was told to put it in the source packages and it would be brought along, so I have done that.
File Structure:
Project
-Source Packages
-src
~Java Classes
-defaultFiles
~Defaults.txt
The code I am trying to use is this:
BufferedReader in;
try {
URL resourceURL = FuelProperties.class.getResource("/defaultFiles/Defaults.txt");
in = new BufferedReader(new FileReader(resourceURL.getPath()));
}
And this works perfectly when I run it through NetBeans but when I build the project and try to run it from the jar file it is not grabbing the file.
I have verified that the default file is being built and exists in the same file structure shown above.
If you can help me out with this I would be extremely grateful as I have no idea what is keeping this from working. Thanks.

You have to lookup in the classpath, not on the disk.
The API to use is :
URL resourceURL : this.getClass().getResource("relative path in the classpath");
Once you have the url you can open a stream, etc.
EDIT : in the main method, you of course need to replace
this.getClass()
by
ClassName.class

I found the answer after searching through a couple dozen questions. It turns out that you can only get a InputStream of the data within a file within your JAR not a File object like I was attempting to do.
(If you want the File object you just have to extract the files from the JAR in your program and then you have access to it.)
So the code that got my problem to work was simply replacing this:
URL resourceURL = FuelProperties.class.getResource("/defaultFiles/Defaults.txt");
in = new BufferedReader(new FileReader(resourceURL.getPath()));
With this:
in = new BufferedReader(new InputStreamReader(this.getClass().getResourceAsStream("/defaultFiles/Defaults.txt")));
And now it is working both inside NetBeans and in the Built JAR file.