this.getClass().getClassLoader().getResource("...") and NullPointerException

Question

I have created a minimal maven project with a single child module in eclipse helios.

In the src/test/resources folder I have put a single file "install.xml". In the folder src/test/java I have created a single package with a single class that does:

  @Test   public void doit() throws Exception {     URL url = this.getClass().getClassLoader().getResource("install.xml");     System.out.println(url.getPath());    } 

but when I run the code as a junit 4 unit test I just get a NullPointerException. This has worked fine a million of times before. Any ideas?

I have followed this guide:

http://www.fuyun.org/2009/11/how-to-read-input-files-in-maven-junit/

but still get the same error.

Answer 1

When you use

this.getClass().getResource("myFile.ext") 

getResource will try to find the resource relative to the package. If you use:

this.getClass().getResource("/myFile.ext") 

getResource will treat it as an absolute path and simply call the classloader like you would have if you'd done.

this.getClass().getClassLoader().getResource("myFile.ext") 

The reason you can't use a leading / in the ClassLoader path is because all ClassLoader paths are absolute and so / is not a valid first character in the path.