code: public static InputStream loadResourceAsStream(final String resourceName) throws IOException {
  
          final InputStream inputStream = findResourceAsStream(resourceName);
          if (inputStream != null) {
              return inputStream;
          }
  
          // No way to obtain that resource, so we must raise an IOException
          throw new IOException("Could not locate resource '" + resourceName + "' in the application's class path");
  
      }
docs: <p>
  Obtain a resource by name, throwing an exception if it is not present.
  </p>
  <p>
  First the <em>context class loader</em> will be used. If this class loader is not
  able to locate the resource, then the <em>class class loader</em>
  ({@code ClassLoaderUtils.class.getClassLoader()}) will be used if it is different from
  the thread context one. Last, the System class loader will be tried.
  </p>
  <p>
  This method does never return {@code null}.
  </p>
  
  @param resourceName the name of the resource to be obtained.
  @return an input stream on the resource (null never returned).
  @throws IOException if the resource could not be located.
  
  @since 3.0.3