java relative path

Question

Using the snippet below throws me a null pointer exception, but i can't find the reason:

String path = ResourcesLoader.class.getResource("src/i3d/resourcesloader/libraries/lib.txt").toString();

Am i using the getResources wrong? I even tried to enter the full path, like "D:\Workspace...", double backslashes, double forwardslashes but i get the exception of null pointer. The only thing i haven't tried is using java's path separator, but that shouldn't be a problem at this moment as it runs on Windows. What do i miss?

Thanks!

Solution 1

getResource searches via the classloader, so typically and simplified in the classpath. The src folder is not in the classpath – it only exists for the build. Depending on your build system (ANT, Maven, IDE internal) a resources folder may be merged into the classpath. You put your resource directly into the source folder which will also work (if the build process copies all non-Java resources to the class output folder or if the source folder is used for the output of the generated classes).

/ is the root for your resources if you use absolute resource locations. It is equivalent to the root within the src folder. /i3d/resourcesloader/libraries/lib.txt would be the correct way to access the resource.

It would be nicer to separate the resources in a separate folder that is merged by the build tool (e.g. in Maven: /src/main/java, /src/main/resources).

Solution 2

You should only provide relative path from your classloading point (ie without src):

String path = ResourcesLoader.class.getResource("/i3d/resourcesloader/libraries/lib.txt").toString();

Solution 3

It seems you are using NetBeans?

Just create a folder called src\resources, get your files inside there, and call this.getClass().getResource("lib.txt");.

Netbeans will pack that properly when building and the resources will be in the main folder inside the jar, so you can get without having to specify their folder.

Comments

[nidhin]

What about i3d/resourcesloader/libraries/lib.txt

[Admin]

What happens if you remove the src part from your path?

[MRM]

i've tried your way but it does't seem to find the file;still null pointer. using the /i3d/resourcesloader/libraries/lib.txt works though.

[MRM]

/i3d/resourcesloader/libraries/lib.txt works just fine,thx.

[MRM]

...it looks like if i use /i3d/resourcesloader/libraries/lib.txt i can't pass the string to a file constructor because it acts like it creates an empty file, not linking with the existing one at that adress. Instead, if i use src/i3d/resourcesloader/libraries/lib.txt in the File constructor it reads the existing one. I'm confused!

[Hauke Ingmar Schmidt]

getResource returns an URL. Use this, don't toString it. Better yet: In most cases you can just use getResourceAsStream and don't need any manual work with file handles.