NullPointerException with Null Context Class Loader

[jghansell]

I ran into a NullPointerException in Configurations.java while attempting to compress an image within a Netty worker thread, which has a null context class loader.

Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.ClassLoader.getResourceAsStream(String)" because the return value of "java.lang.Thread.getContextClassLoader()" is null                                                                                                                               
      at net.coobird.thumbnailator.util.Configurations.init(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                                                              
      at net.coobird.thumbnailator.util.Configurations.<clinit>(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                                                          
      at net.coobird.thumbnailator.tasks.io.InputStreamImageSource.<init>(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                                                
      at net.coobird.thumbnailator.Thumbnails$Builder$InputStreamImageSourceIterator$1.next(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                              
      at net.coobird.thumbnailator.Thumbnails$Builder$InputStreamImageSourceIterator$1.next(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                              
      at net.coobird.thumbnailator.Thumbnails$Builder.toFile(Unknown Source) ~[thumbnailator-0.4.20.jar:0.4.20]                                                                                                                                                                                                                                                                                                                                                                                                                     
      ...

Which traces back to this statement in Configurations.init():

InputStream resourceIs = Thread.currentThread()
        .getContextClassLoader()
        .getResourceAsStream("thumbnailator.properties");

I'm working around it in my own environment by temporarily setting the context class loader to getClass().getClassLoader() before running Thumbnails.Builder.toFile().