Ali
Ali

Reputation: 267077

getClassLoader().getResource() returns null

I have this test app:

import java.applet.*;
import java.awt.*;
import java.net.URL;
public class Test extends Applet
{

    public void init()
    {
        URL some=Test.class.getClass().getClassLoader().getResource("/assets/pacman.png");
        System.out.println(some.toString());
        System.out.println(some.getFile());
        System.out.println(some.getPath());

    }
}

When I run it from Eclipse, I get the error:

java.lang.NullPointerException
    at Test.init(Test.java:9)
    at sun.applet.AppletPanel.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

Classpath (from .CLASSPATH file)

<classpathentry kind="src" path="src"/>

In my c:\project\src folder, I have only the Test.java file and the 'assets' directory which contains pacman.png.

What am I doing wrong and how to resolve it?

Upvotes: 16

Views: 49548

Answers (5)

Hossein Mousavi
Hossein Mousavi

Reputation: 11

I found that the 'resouces' file is a normal file type

enter image description here

Then my code worked

URL url = FileUtility.class.getClassLoader().getResource("test.json");

Upvotes: 0

namalfernandolk
namalfernandolk

Reputation: 9134

  • When you use .getClass().getResource(fileName) it considers the location of the fileName is the same location of the of the calling class.
  • When you use .getClass().getClassLoader().getResource(fileName) it considers the location of the fileName is the root - in other words bin folder

It hits NullPointerException if the file is actually not exist there.

Source:

package Sound;
public class ResourceTest {
    public static void main(String[] args) {
        String fileName = "Kalimba.mp3";
        System.out.println(fileName);
        System.out.println(new ResourceTest().getClass().getResource(fileName));
        System.out.println(new ResourceTest().getClass().getClassLoader().getResource(fileName));

Output:

Kalimba.mp3
file:/C:/Users/User/Workspaces/MyEclipse%208.5/JMplayer/bin/Sound/Kalimba.mp3
file:/C:/Users/User/Workspaces/MyEclipse%208.5/JMplayer/bin/Kalimba.mp3
    }
}

Upvotes: 8

Thinhbk
Thinhbk

Reputation: 2214

This works for me:

URL viaClass=Test.class.getResource("assets/test.html");

which assets in the same folder with Test.class output file (after a miserable checking and debugging)

Upvotes: 1

TofuBeer
TofuBeer

Reputation: 61526

I would do it this way:

final InputStream stream;

stream = Test.class.getResourceAsStream("assets/pacman.png");
System.out.println("Stream = " + stream);

"/assets/pacman.png" is an absolute location whle "assets/pacman.png" is a relative location.

Upvotes: 8

Jon Skeet
Jon Skeet

Reputation: 1500675

You don't need the slash at the start when getting a resource from a ClassLoader, because there's no idea of a "relative" part to start with. You only need it when you're getting a resource from a Class where relative paths go from the class's package level.

In addition, you don't want Test.class.getClass() as that gets the class of Test.class, which will be Class<Class>.

In other words, try either of these lines:

URL viaClass=Test.class.getResource("/assets/pacman.png");
URL viaLoader=Test.class.getClassLoader().getResource("assets/pacman.png");

Upvotes: 23

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