Avoid enumerating every jar entry in FileUtil::listResourceDirectory

Use 'java.nio.file.FileSystem' in place of 'java.util.jar.JarFile' to
list all the resources under a given classpath (on Windows & Linux), as
that is a bit neater and potentially more efficient than scanning the
entire ZIP directory structure.

common/src/main/java/bisq/common/file/FileUtil.java

@@ -24,11 +24,12 @@
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
 
+import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
-import java.net.URLDecoder;
 
-import java.nio.charset.StandardCharsets;
+import java.nio.file.FileSystem;
+import java.nio.file.FileSystems;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
@@ -37,14 +38,13 @@
 import java.io.IOException;
 import java.io.InputStream;
 
-import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.Date;
-import java.util.Enumeration;
 import java.util.List;
-import java.util.jar.JarEntry;
-import java.util.jar.JarFile;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import lombok.extern.slf4j.Slf4j;
 
@@ -177,38 +177,31 @@ public static void resourceToFile(String resourcePath,
         }
     }
 
-    // adapted from https://stackoverflow.com/questions/3923129/get-a-list-of-resources-from-classpath-directory/48190582#48190582
     public static List<String> listResourceDirectory(String directoryName) throws IOException, ResourceNotFoundException {
         URL url = Thread.currentThread().getContextClassLoader().getResource(directoryName);
         if (url == null) {
             throw new ResourceNotFoundException(directoryName);
         }
+        URI uri;
+        try {
+            uri = url.toURI();
+        } catch (URISyntaxException e) {
+            throw new IOException(e);
+        }
         if (url.getProtocol().equals("file")) {
-            try {
-                File dir = new File(url.toURI());
-                String[] filenames = dir.list();
-                if (filenames != null) {
-                    return List.of(filenames);
-                }
-            } catch (URISyntaxException e) {
-                throw new IOException(e);
+            File dir = new File(uri);
+            String[] filenames = dir.list();
+            if (filenames != null) {
+                return List.of(filenames);
             }
         } else if (url.getProtocol().equals("jar")) {
-            List<String> filenames = new ArrayList<>();
-            String dirname = directoryName + "/";
-            String path = url.getPath();
-            String jarPath = path.substring(5, path.indexOf("!"));
-            try (JarFile jar = new JarFile(URLDecoder.decode(jarPath, StandardCharsets.UTF_8.name()))) {
-                Enumeration<JarEntry> entries = jar.entries();
-                while (entries.hasMoreElements()) {
-                    JarEntry entry = entries.nextElement();
-                    String name = entry.getName();
-                    if (name.startsWith(dirname) && !dirname.equals(name)) {
-                        filenames.add(name.substring(dirname.length()));
-                    }
-                }
+            try (FileSystem fileSystem = FileSystems.newFileSystem(uri, Collections.emptyMap());
+                 Stream<Path> filePaths = java.nio.file.Files.walk(fileSystem.getPath(directoryName), 1)) { //NOPMD
+                return filePaths
+                        .skip(1)
+                        .map(path -> path.getFileName().toString())
+                        .collect(Collectors.toUnmodifiableList());
             }
-            return filenames;
         }
         throw new IOException("Failed to list resource directory: " + directoryName);
     }