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

Issue

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.

Solution

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.

Answered By - AmishDave