[FIXED] How can I package a resource file into a runnable jar

Issue

I have tried this in many ways, and followed several online instructions, such as this - Eclipse exported Runnable JAR not showing images But so far, no success.

I have a very simple program that reads a text file (test.txt) and prints out its contents to standard output. I am using Eclipse. Here is what I have done-

• I put the text file into a folder called 'resources'
• I right-clicked the resources folder, selected "Build path" and hit "Use as resource folder"
• In my code, I tried two ways of addressing the file - (a) as "/test.txt" and (b) as "resources/test.txt. The latter method works when I run the program within Eclipse. However, neither method works when I export the project as a runnable jar file. The resource folder fails to be included in the jar file.

Any help will be much appreciated.

Addendum: Here is the code.

public class FileIOTest {

public static void main(String[] args) {
    String line;
    try {
        BufferedReader br = new BufferedReader(new FileReader(new File("/test.txt")));
        while((line = br.readLine()) != null){
            System.out.println(line);
        }

    br.close(); 
    }
    catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}

}

}

Solution

You can not access a resource in a Jar file through a FileReader because it is not a file on the file system. Java does have a mechanism for accessing resources in your classpath (including in Jars): ClassLoader.getResourceAsStream(). You can use it with your default classloader:

BufferedReader br = new BufferedReader(new InputStreamReader(
                        ClassLoader.getSystemClassLoader()
                                   .getResourceAsStream("test.txt")));

Note that getResourceAsStream returns null instead of throwing an exception, so you may want to get the stream first, check if for null, then either throw an exception or process it.

You will want to give the full path within the jar as your path.

Answered By - Mad Physicist
Answer Checked By - Clifford M. (JavaFixing Volunteer)