Question

I have a folder with Tomcat7 installed on my disk that I use to do some tests on my web application running it from eclipse and it I works well. When I try to deploy the application on a stand alone tomcat server it gives an error: (I’m using windows)

Fev 08, 2012 9:10:04 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Allocate exception for servlet Process
java.lang.NullPointerException
    at hs.server.CommandFactory.<init>(CommandFactory.java:27)
    at hs.server.Process.init(Process.java:40)

and the line 27 is in this context:

19-String pathname = "/"+packageName.replace(".", "/")+"/";
20      //String pathname = packageName.replace(".", "/");
21-     URL resource = loader.getResource(pathname);
22-     File commandDir = (new File(resource.getFile()));
23-     
24-     //File commandDir = new File(loader.getResource(packageName.replace(".",   25-"/")).getFile());
26-
27-     for(String classFilepath: commandDir.list()) {

I guess is something about the URL but the problem is that I’m running it without any problems on the tomcat instance on eclipse. Thank you

Answer 1

File.list() will return null if File represents a non-existent directory. This null will then cause your for loop to throw a null-pointer exception.

You need to make your code defensive, and check that the directory exists using the methods on File before you attempt to read it.