Java jar在Maven资源文件夹中找不到文件

Question

I use maven and have a textfile in a sourcefolder called src/main/resources when I try to load a file from within the folder on my local system it works well

BufferedReader reader = new BufferedReader(new InputStreamReader(this.getClass().getResourceAsStream("/stopwords_german.txt")));

but as soon as I export the project as Runnable Jar in Eclipse and start the jar on my Server I get a Nullpointer exception

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:622)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: java.lang.NullPointerException
    at java.io.Reader.<init>(Reader.java:78)
    at java.io.InputStreamReader.<init>(InputStreamReader.java:72)
    at de.test.dataminer.helper.FilterText.initStopwords(FilterText.java:43)

It's the line with the BufferedReader.

I saw very similar questions here but nothing worked out so for that I tested to fix it ( like to try with classloader ). Anyone a pointer?

    <resources>
      <resource>
        <directory>/home/johnny/workspace/dataminer/src/main/resources</directory>
      </resource>
    </resources>

Answer 1

A Check: simply open the jar (ziip format) with 7zip or so. The file name should be case-sensitive (whereas Windows is case-insensitive). This could also be tested by running the jar outside the IDE.

A remark: add the encoding to the InputStreamReader, otherwise the current operating system encoding is taken - non-portable.

BufferedReader reader = new BufferedReader(
        new InputStreamReader(
            this.getClass().getResourceAsStream("/stopwords_german.txt"),
            "Cp1252"));

If everything fits, still something might go wrong: getClass() might be (maybe through inheritance) some class outside the jar. Then you either do something like SomeClassInJar.class.getResource , or use a ClassLoader.getResourceAsStrean("stopwords_german.txt") without slash in front.