--- a/jdk/src/jdk.jlink/share/classes/jdk/tools/jlink/builder/DefaultImageBuilder.java	Wed Jan 18 11:47:36 2017 +0000
+++ b/jdk/src/jdk.jlink/share/classes/jdk/tools/jlink/builder/DefaultImageBuilder.java	Wed Jan 18 19:35:41 2017 +0530
@@ -165,18 +165,9 @@
                 throw new PluginException("TargetPlatform attribute is missing for java.base module");
             }
 
-            Path bin = root.resolve(BIN_DIRNAME);
+            checkResourcePool(files);
 
-            // check any duplicated resource files
-            Map<Path, Set<String>> duplicates = new HashMap<>();
-            files.entries()
-                .filter(f -> f.type() != ResourcePoolEntry.Type.CLASS_OR_RESOURCE)
-                .collect(groupingBy(this::entryToImagePath,
-                         mapping(ResourcePoolEntry::moduleName, toSet())))
-                .entrySet()
-                .stream()
-                .filter(e -> e.getValue().size() > 1)
-                .forEach(e -> duplicates.put(e.getKey(), e.getValue()));
+            Path bin = root.resolve(BIN_DIRNAME);
 
             // write non-classes resource files to the image
             files.entries()
@@ -185,13 +176,8 @@
                     try {
                         accept(f);
                     } catch (FileAlreadyExistsException e) {
-                        // error for duplicated entries
-                        Path path = entryToImagePath(f);
-                        UncheckedIOException x =
-                            new UncheckedIOException(path + " duplicated in " +
-                                    duplicates.get(path), e);
-                        x.addSuppressed(e);
-                        throw x;
+                        // Should not happen! Duplicates checking already done!
+                        throw new AssertionError("Duplicate entry!", e);
                     } catch (IOException ioExp) {
                         throw new UncheckedIOException(ioExp);
                     }
@@ -242,6 +228,27 @@
         }
     }
 
+    private void checkResourcePool(ResourcePool pool) {
+        // For now, only duplicate resources check. Add more checks here (if any)
+        checkDuplicateResources(pool);
+    }
+
+    private void checkDuplicateResources(ResourcePool pool) {
+        // check any duplicated resources
+        Map<Path, Set<String>> duplicates = new HashMap<>();
+        pool.entries()
+             .filter(f -> f.type() != ResourcePoolEntry.Type.CLASS_OR_RESOURCE)
+             .collect(groupingBy(this::entryToImagePath,
+                      mapping(ResourcePoolEntry::moduleName, toSet())))
+             .entrySet()
+             .stream()
+             .filter(e -> e.getValue().size() > 1)
+             .forEach(e -> duplicates.put(e.getKey(), e.getValue()));
+        if (!duplicates.isEmpty()) {
+            throw new PluginException("Duplicate resources: " + duplicates);
+        }
+    }
+
     /**
      * Generates launcher scripts.
      *

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/tools/jlink/ResourceDuplicateCheckTest.java	Wed Jan 18 19:35:41 2017 +0530
@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8168254
+ * @summary Detect duplicated resources in packaged modules
+ * @modules jdk.jlink/jdk.tools.jlink.builder
+ *          jdk.jlink/jdk.tools.jlink.internal
+ * @run build ResourceDuplicateCheckTest
+ * @run main ResourceDuplicateCheckTest
+ */
+
+import java.net.URI;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import jdk.tools.jlink.builder.DefaultImageBuilder;
+import jdk.tools.jlink.internal.ResourcePoolEntryFactory;
+import jdk.tools.jlink.internal.ResourcePoolManager;
+import jdk.tools.jlink.plugin.PluginException;
+import jdk.tools.jlink.plugin.ResourcePoolEntry;
+
+public class ResourceDuplicateCheckTest {
+    public static void main(String[] args) throws Exception {
+        new ResourceDuplicateCheckTest().test();
+    }
+
+    public void test() throws Exception {
+        ResourcePoolManager input = new ResourcePoolManager();
+        // need java.base module info because OS name is retrieved from it from storeFiles
+        input.add(ResourcePoolEntryFactory.create("/java.base/module-info.class",
+                    ResourcePoolEntry.Type.CLASS_OR_RESOURCE, getJavaBaseModuleInfo()));
+
+        // same NATIVE_CMD from two different modules
+        input.add(newInMemoryImageFile("/com.acme/bin/myexec",
+                    ResourcePoolEntry.Type.NATIVE_CMD, "mylib"));
+        input.add(newInMemoryImageFile("/com.foo/bin/myexec",
+                    ResourcePoolEntry.Type.NATIVE_CMD, "mylib"));
+        Path root = Paths.get(System.getProperty("test.classes"));
+        DefaultImageBuilder writer = new DefaultImageBuilder(root, Collections.emptyMap());
+        try {
+            writer.storeFiles(input.resourcePool());
+        } catch (PluginException pe) {
+            if (! pe.getMessage().contains("Duplicate resources:")) {
+                throw new AssertionError("expected duplicate resources message");
+            }
+        }
+    }
+
+    private byte[] getJavaBaseModuleInfo() throws Exception {
+        Path path = FileSystems.
+                getFileSystem(URI.create("jrt:/")).
+                getPath("/modules/java.base/module-info.class");
+        return Files.readAllBytes(path);
+    }
+
+    private static ResourcePoolEntry newInMemoryImageFile(String path,
+            ResourcePoolEntry.Type type, String content) {
+        return ResourcePoolEntryFactory.create(path, type, content.getBytes());
+    }
+}