How to access file within jar file?

Question

I have properties file in my application's classpath. Before creating jar file for this application there is no problem but when I create jar file and run it using java -jar command it returns null pointer exception. Here is my code to load properties:

private Properties loadProperties() {
    Properties prop = new Properties();
    InputStream input = null;

    try {
        input = this.getClass().getResourceAsStream("./auth");
        prop.load(input);
    } catch (IOException ex) {
        ex.printStackTrace();
    } finally {
        if (input != null) {
            try {
                input.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return prop;
}

Can I access property file within jar or it is not possible?

Here is exception I get:

Exception in thread "main" java.lang.NullPointerException
    at java.util.Properties$LineReader.readLine(Properties.java:434)
    at java.util.Properties.load0(Properties.java:353)
    at java.util.Properties.load(Properties.java:341)
    at com.kadir.MyApp.loadProperties(MyApp.java:109)
    at com.kadir.MyApp.<init>(MyApp.java:62)
    at com.kadir.MyApp.main(MyApp.java:48)

and lines 108 and 109 are these:

    input =this.getClass().getClassLoader().getResourceAsStream("auth");
    prop.load(input);

One more note: I am developing my app on Windows but running it on Linux, error may come from this

here you go: http://stackoverflow.com/questions/5171957/access-file-in-jar-file — , May 07 '16 at 19:38
show your code, show stacktrace and point the line, where you get NullPointerException — , May 07 '16 at 19:58
are you using "auth" or "./auth" as the path? also, whats the "path" for the file inside the actual jar? — radai, May 07 '16 at 20:05
where is the your file in your jar file and what is the package name of the class that has the method loadProperties? — Nicolas Filotto, May 07 '16 at 20:07
@radai I tried both auth and ./auth but no luck. And file has same path with classpath of MyApp class — kadir, May 07 '16 at 20:07
file has same path with the file MyApp.class and the package name is com.kadir @NicolasFilotto — kadir, May 07 '16 at 20:10
try the full path instead this.getClass().getResourceAsStream("/com/kadir/auth") — Nicolas Filotto, May 07 '16 at 20:10
I have just tried to access a file into a jar, it could work on my side using MyClass.class.getResourceAsStream("/path/to/my/file") (absolute path) and MyClass.class.getResourceAsStream("file") (relative path as the class and the file are both into the same folder) but it didn't work with ./file so your issue is elsewhere — Nicolas Filotto, May 07 '16 at 20:28

score 0 · Accepted Answer · answered May 07 '16 at 21:33

I don't know the exact reason for why it wasn't working but changing these two lines

input = this.getClass().getResourceAsStream("auth");
prop.load(input);

to these:

ClassLoader classloader = Thread.currentThread().getContextClassLoader();
input = classloader.getResourceAsStream("auth");
prop.load(input);

made my code working

How to access file within jar file?

1 Answers1