I have a jar file which contain some text file inside, I am trying to load the file as: InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path); It doesn't work as error showing : If I try to extract the resource file into classpath src/main/resources, then it is working fine. My question is, could we read resource file from Jar (when running in GraalVM

GraalVM native-image how to read resource file from Jar

I have a jar file which contain some text file inside, I am trying to load the file as:

InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path);

It doesn’t work as error showing :

[SUB] java.lang.NullPointerException
[Thu Aug 27 12:07:48 SGT 2020][INFO] [SUB]  at java.io.Reader.<init>(Reader.java:167)
[Thu Aug 27 12:07:48 SGT 2020][INFO] [SUB]  at hellofx.HelloFX.readFileAsStringFromJar(HelloFX.java:116)
[Thu Aug 27 12:07:48 SGT 2020][INFO] [SUB]  at hellofx.HelloFX.test(HelloFX.java:107)

If I try to extract the resource file into classpath src/main/resources, then it is working fine.

My question is, could we read resource file from Jar (when running in GraalVM native-image)? There are plenty of third party Java libraries which are reading the resource files that are bundled together in the same Jar, how could we overcome this?

PS update:

it is indeed my mistake, confused with class.getResource() and class.getClassLoader().getResource(). One require slash in the beginning and another doesn’t allow. Once I removed the slash in path variable, it is working fine.

Answer

You need to tell native image what resources to include via -H:IncludeResources=path. The value can be a regular expression.

See the documentation for more details: https://github.com/oracle/graal/blob/master/docs/reference-manual/native-image/Resources.md

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Answer