Cannot read resource from jar

Issue

I have the following prefix:

String prefix = TemplatesReader.class.getClassLoader().getResource("templates/").getPath();

and have method

public byte[] read(String pathToTemplate) {
   return Files.readAllBytes(Paths.get(prefix + pathToTemplate));
}

in intellij idea works correctly, but when starting jar an error occurs:

java.nio.file.NoSuchFileException: file:/app.jar!/BOOT-INF/classes!/templates/request-orders/unmarked/RequestOrderUnmarked.pdf

Solution

You must not assume that a resource is a file. When the resource is inside a .jar file, it is a part of that .jar file; it is no longer a separate file at all.

You cannot use Files or Paths to read the resource.

You cannot use the getPath() method of URL. It does not return a file name. It only returns the path portion of the URL (that is, everything between the URL’s scheme/authority and its query portion), which is not a file path at all.

Instead, read the resource using getResourceAsStream:

private static final String RESOURCE_PREFIX = "/templates/";

public byte[] read(String pathToTemplate)
throws IOException {
    try (InputStream stream = TemplatesReader.class.getResource(
        RESOURCE_PREFIX + pathToTemplate)) {

        return stream.readAllBytes();
    }
}

Answered By - VGR