Using getResourceAsStream is not working in Java [duplicate]

Question

I have a very simple method which uses the getclass().getResourceAsStream() method to read a file. However it always returns null and I can't figure out what is wrong. Here is my piece of code.

InputStream sw = getClass().getResourceAsStream("/filename.txt");
BufferedReader bf = new BufferedReader( new InputStreamReader(sw));

sw always remain null. the file filename.txt exist in the root directory of my project.

EDIT: I found the reason. I realized that I was running my project from Eclipse and the project was not part of the classpath on my PC. However if I package my program as a jar file and then run it, the files in the jar file are considered as resources and can be read using the getResourceAsStream() method.

Answer 1

Root of your project is not always the root of the path from the ClassLoader point of view. Easiest way to find out where it is trying to load the resource from:

System.out.println(MyClass.class.getResource("/").getPath());

And after that you may be able to easily find out the part of the project or run configuration that causes the difference between your assumption and the reality about the right placement of the file.

Answer 2

The method Class.getResourceAsStream() looks for the designated resource within the Java class path, not based on the project root.

The project root usually is not part of the classpath. Instead, you should have a src folder (or a similar name), which contains the Java files and may also contain your text file. Or, if you use Maven, you have folders src/main/java and src/main/resources, which are classpath roots. In this case, the text file should reside in the resources folder.

If your project gets packaged into a .jar file, all its resources are packaged in the .jar file along with the .class files, and will be found by Class.getResourceAsStream().