class.getResourceAsStream在用户计算机上返回null，如何重现？

Question

I have an issue reported by an user which I cannot reproduce. The issue is error:

Exception in thread "main" java.lang.NullPointerException: source at java.util.Objects.requireNonNull(Unknown Source) at java.util.Scanner.(Unknown Source) at cz.autoclient.Main.getVersion( Main.java:86 ) at cz.autoclient.Main.( Main.java:76 ) at cz.autoclient.Main.main( Main.java:262 )

In this code:

   private VersionId VERSION = new VersionId("0.0-error");
   public final VersionId getVersion() {
     if(VERSION.affix.equals("error")) {
       InputStream in = Main.class.getResourceAsStream("/version");
       Scanner sc = new Scanner(in, "UTF-8"); // LINE 86
       VERSION = new VersionId(sc.useDelimiter("\\A").next());
     }
     return VERSION;
   }

What I do here is to parse internal resource which contains version info for the application (including version as variable turned out to be very impractical).

Version file might look something like this:

v3.5-beta

The error seems to be caused by the resource "/version" being unreachable. This error does only seem to happen to the user, so I need help why it even might happen. User's Java version is:

java version "1.8.0_101"
Java(TM) SE Runtime Environment (build 1.8.0_101-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)

Here is the full Main.java (specific commit) . The application is distributed as jar file. The version file is in the root of the jar file.

In case it happened to be unclear the problem is when I run the same release (downloaded from release site, not re-built), I do not encounter the problem . I asked the user to verify that the file is there (by unziping the jar file). He sent it to me, it was intact .

Answer 1

Evidently you ran the code in your IDE, which doesn't use the built JAR file at all: it uses the directory hierarchy produced by the compilation step. All you you have to do here is check the content of the JAR file you shipped, which obviously does not contain /version . The way to reproduce this problem is to run the same JAR file the same way the customer did, in a clean install. However that's not what you're really asking. The solution is to get rid of the resource, and put the version information into the JAR manifest, where you can't forget to ship it.

Answer 2

User claims that he uninstalled MacAfee antivirus (distributed with their PC) and replaced it with Avast! and that this fixed the problem. Not exactly a programming answer but I decided to share this in case someone faces the same problem.