Correctly open URLs for reading

license-maven-plugin/src/main/java/com/mycila/maven/plugin/license/util/FileUtils.java

@@ -23,6 +23,7 @@
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
+import java.io.InputStreamReader;
 import java.io.IOException;
 import java.io.Reader;
 import java.io.UncheckedIOException;
@@ -34,7 +35,6 @@
 import java.nio.charset.Charset;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.Map;
 import java.util.stream.Stream;
 
@@ -57,24 +57,26 @@ public static void write(File file, String content, Charset encoding) throws IOE
     }
   }
 
+  private static Reader urlToReader(URL url, Charset encoding) throws IOException {
+    return new BufferedReader(new InputStreamReader(url.openStream(), encoding));
+  }
+
   public static String read(URL location, Charset encoding, Map<String, Object> properties) throws IOException, URISyntaxException {
-    try (Reader reader = new InterpolationFilterReader(Files.newBufferedReader(Paths.get(location.toURI()), encoding), properties)) {
+    try (Reader reader = new InterpolationFilterReader(urlToReader(location, encoding), properties)) {
       return IOUtils.toString(reader);
     }
   }
 
   public static String read(URL location, Charset encoding) throws IOException, URISyntaxException {
-    try (Reader reader = Files.newBufferedReader(Paths.get(location.toURI()), encoding)) {
+    try (Reader reader = urlToReader(location, encoding)) {
       return IOUtils.toString(reader);
     }
   }
 
   public static String[] read(final URL[] locations, final Charset encoding) throws IOException, URISyntaxException {
     final String[] results = new String[locations.length];
     for (int i = 0; i < locations.length; i++) {
-      try (Reader reader = Files.newBufferedReader(Paths.get(locations[i].toURI()), encoding)) {
-        results[i] = IOUtils.toString(reader);
-      }
+      results[i] = read(locations[i], encoding);
     }
     return results;
   }

license-maven-plugin/src/test/java/com/mycila/maven/plugin/license/util/FileUtilsTest.java

@@ -19,9 +19,31 @@
 import org.junit.jupiter.api.Test;
 
 import java.io.File;
+import java.net.URL;
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
 
 class FileUtilsTest {
+  @Test
+  void test_jar_url_read() {
+    // the assumption here is, that junit's @Test class is within a jar on the classpath
+    URL resourceUrl = Test.class.getResource("/" + Test.class.getName().replace('.', '/') + ".class");
+    final Charset encoding = StandardCharsets.US_ASCII;
+    final String magic = encoding.decode(ByteBuffer.wrap(new byte[]{(byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE})).toString();
+
+    String singlePlainContent = Assertions.assertDoesNotThrow(() -> FileUtils.read(resourceUrl, encoding));
+    Assertions.assertEquals(magic, singlePlainContent.substring(0, 4));
+
+    String[] multipleContents = Assertions.assertDoesNotThrow(() -> FileUtils.read(new URL[]{ resourceUrl, resourceUrl }, encoding));
+    Assertions.assertEquals(2, multipleContents.length);
+    Assertions.assertEquals(magic, multipleContents[0].substring(0, 4));
+    Assertions.assertEquals(magic, multipleContents[1].substring(0, 4));
+
+    String interpolatedContent = Assertions.assertDoesNotThrow(() -> FileUtils.read(resourceUrl, encoding, new HashMap<>()));
+    Assertions.assertEquals(magic, interpolatedContent.substring(0, 4));
+  }
 
   @Test
   void test_read_first_lines() throws Exception {