[java] Different ways of loading a file as an InputStream

What's the difference between:

InputStream is = this.getClass().getClassLoader().getResourceAsStream(fileName)

and

InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName)

and

InputStream is = this.getClass().getResourceAsStream(fileName)

When are each one more appropriate to use than the others?

The file that I want to read is in the classpath as my class that reads the file. My class and the file are in the same jar and packaged up in an EAR file, and deployed in WebSphere 6.1.

All these answers around here, as well as the answers in this question, suggest that loading absolute URLs, like "/foo/bar.properties" treated the same by class.getResourceAsStream(String) and class.getClassLoader().getResourceAsStream(String). This is NOT the case, at least not in my Tomcat configuration/version (currently 7.0.40).

MyClass.class.getResourceAsStream("/foo/bar.properties"); // works!  
MyClass.class.getClassLoader().getResourceAsStream("/foo/bar.properties"); // does NOT work!

Sorry, I have absolutely no satisfying explanation, but I guess that tomcat does dirty tricks and his black magic with the classloaders and cause the difference. I always used class.getResourceAsStream(String) in the past and haven't had any problems.

PS: I also posted this over here

After trying some ways to load the file with no success, I remembered I could use FileInputStream, which worked perfectly.

InputStream is = new FileInputStream("file.txt");

This is another way to read a file into an InputStream, it reads the file from the currently running folder.

Use MyClass.class.getClassLoader().getResourceAsStream(path) to load resource associated with your code. Use MyClass.class.getResourceAsStream(path) as a shortcut, and for resources packaged within your class' package.

Use Thread.currentThread().getContextClassLoader().getResourceAsStream(path) to get resources that are part of client code, not tightly bounds to the calling code. You should be careful with this as the thread context class loader could be pointing at anything.

It Works , try out this :

InputStream in_s1 =   TopBrandData.class.getResourceAsStream("/assets/TopBrands.xml");

Plain old Java on plain old Java 7 and no other dependencies demonstrates the difference...

I put file.txt in c:\temp\ and I put c:\temp\ on the classpath.

There is only one case where there is a difference between the two call.

class J {

 public static void main(String[] a) {
    // as "absolute"

    // ok   
    System.err.println(J.class.getResourceAsStream("/file.txt") != null); 

    // pop            
    System.err.println(J.class.getClassLoader().getResourceAsStream("/file.txt") != null); 

    // as relative

    // ok
    System.err.println(J.class.getResourceAsStream("./file.txt") != null); 

    // ok
    System.err.println(J.class.getClassLoader().getResourceAsStream("./file.txt") != null); 

    // no path

    // ok
    System.err.println(J.class.getResourceAsStream("file.txt") != null); 

   // ok
   System.err.println(J.class.getClassLoader().getResourceAsStream("file.txt") != null); 
  }
}