Set Path To File In Jar App

What I do wrong when I trying to set path to file in my jar app. I have application which work with xml file. I have next project structure:

/project_root_directory
|_  /lib
|_  /resources/file.xml
|_  /src
 
So, I need to set correctly path to my jar file, because when I running it from IDE, it works nice. By default it seems:

private File file;
private StreamResult streamResult;
file = new File("resources/file.xml");
streamResult = new StreamResult(file);

And methods where I can modify the DOM structure via transformer in end of methods:

transformer.transform(source, streamResult);

So, I trying set path to file:

private URL url;
...
file = new File(url.getPath());
streamResult = new StreamResult(file);
 
But it didn't not work, because when I trying to get resource by next condition

url = getClass().getResource("resources/file.xml");
url = getClass().getResource("resources/file.xml");url = getClass().getResource(url = getClass().getResource("resources/file.xml");resources/file.xml");
url - is null
Okay..
 
I tried next solution
 
InputStream input = getClass().getResourceAsStream("resources/file.xml"); 
 
There, I got also null....
 
Also, I tried made absolute path
 
filePath = file.getAbsolutePath();
file = new File(filePath);
streamResult = new StreamResult(file);

But it also didn't work. There I got message seems like: "Can't find resource /User/user1/Desktop/program1/resources/file.xml" - but that's really absolute path to a file.
 
Also, I tried made it via System.getProperty

String filename = "file.xml";
String workingDir = System.getProperty("user.dir");
finalfile = workingDir + File.separator + "resources" + File.separator + filename;
file = new File(finalfile);

I also made unit test which completed with "green light", but in jar its wrong with message "Can't find resource /User/user1/Desktop/program1/resources/file.xm" ....