--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/JlinkTask.java	2016-04-12 15:16:04.071011600 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/JlinkTask.java	2016-04-12 15:16:02.220993100 +0530
@@ -70,6 +70,7 @@
  * ## Should use jdk.joptsimple some day.
  */
 public class JlinkTask {
+    private static final boolean DEBUG = Boolean.getBoolean("jlink.debug");
 
     private static <T extends Throwable> void fail(Class<T> type,
             String format,
@@ -215,18 +216,24 @@
             }
 
             return EXIT_OK;
-        } catch (UncheckedIOException | PluginException | IOException | ResolutionException e) {
+        } catch (UncheckedIOException | PluginException | IllegalArgumentException |
+                 IOException | ResolutionException e) {
             log.println(taskHelper.getMessage("error.prefix") + " " + e.getMessage());
-            log.println(taskHelper.getMessage("main.usage.summary", PROGNAME));
+            if (DEBUG) {
+                e.printStackTrace(log);
+            }
             return EXIT_ERROR;
         } catch (BadArgs e) {
             taskHelper.reportError(e.key, e.args);
             if (e.showUsage) {
                 log.println(taskHelper.getMessage("main.usage.summary", PROGNAME));
             }
+            if (DEBUG) {
+                e.printStackTrace(log);
+            }
             return EXIT_CMDERR;
         } catch (Throwable x) {
-            log.println(taskHelper.getMessage("main.msg.bug"));
+            log.println(taskHelper.getMessage("error.prefix") + " " + x.getMessage());
             x.printStackTrace(log);
             return EXIT_ABNORMAL;
         } finally {
--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/DefaultCompressPlugin.java	2016-04-12 15:16:08.191052800 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/DefaultCompressPlugin.java	2016-04-12 15:16:07.321044100 +0530
@@ -125,7 +125,7 @@
                         zip = new ZipPlugin(resFilter);
                         break;
                     default:
-                        throw new PluginException("Invalid level " + level);
+                        throw new IllegalArgumentException("Invalid compression level " + level);
                 }
             } else {
                 ss = new StringSharingPlugin(resFilter);
--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/ExcludeVMPlugin.java	2016-04-12 15:16:12.051091400 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/ExcludeVMPlugin.java	2016-04-12 15:16:11.211083000 +0530
@@ -208,7 +208,7 @@
                     break;
                 }
                 default: {
-                    throw new PluginException("Unknown option " + value);
+                    throw new IllegalArgumentException("Unknown exclude VM option: " + value);
                 }
             }
             predicate = new ResourceFilter(Utils.listParser.apply(exclude), true);
--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/IncludeLocalesPlugin.java	2016-04-12 15:16:16.219313800 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/IncludeLocalesPlugin.java	2016-04-12 15:16:15.337225600 +0530
@@ -162,7 +162,7 @@
                 try {
                     return new Locale.LanguageRange(s);
                 } catch (IllegalArgumentException iae) {
-                    throw new PluginException(String.format(
+                    throw new IllegalArgumentException(String.format(
                         PluginsResourceBundle.getMessage(NAME + ".invalidtag"), s));
                 }
             })
--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/OptimizationPlugin.java	2016-04-12 15:16:20.586750500 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/OptimizationPlugin.java	2016-04-12 15:16:19.707662600 +0530
@@ -273,7 +273,7 @@
             } else if (s.equals(FORNAME_REMOVAL)) {
                 optimizers.add(new ForNameFolding());
             } else {
-                throw new PluginException("Unknown optimization");
+                throw new IllegalArgumentException("Unknown optimization: " + s);
             }
         }
         String f = config.get(LOG);
--- old/src/jdk.jlink/share/classes/jdk/tools/jlink/plugin/Plugin.java	2016-04-12 15:16:24.790170800 +0530
+++ new/src/jdk.jlink/share/classes/jdk/tools/jlink/plugin/Plugin.java	2016-04-12 15:16:23.907082500 +0530
@@ -201,6 +201,8 @@
      * This method is called prior to invoke the plugin.
      *
      * @param config The plugin configuration.
+     * @throws IllegalArgumentException if a mandatory argument is missing or
+     * if an argument has invalid value.
      */
     public default void configure(Map<String, String> config) {
     }
@@ -211,6 +213,9 @@
      *
      * @param config The plugin configuration.
      * @param ctx The plugin context
+     * @throws IllegalArgumentException if a mandatory argument is missing or
+     * if an argument has invalid value.
+     *
      */
     public default void configure(Map<String, String> config, PluginContext ctx) {
         configure(config);
--- old/test/tools/jlink/JLinkTest.java	2016-04-12 15:16:28.883580100 +0530
+++ new/test/tools/jlink/JLinkTest.java	2016-04-12 15:16:28.003492100 +0530
@@ -204,7 +204,7 @@
             String[] userOptions = {"--compress", "invalid"};
             String moduleName = "invalidCompressLevel";
             helper.generateDefaultJModule(moduleName, "composite2");
-            helper.generateDefaultImage(userOptions, moduleName).assertFailure("Error: Invalid level invalid");
+            helper.generateDefaultImage(userOptions, moduleName).assertFailure("Error: Invalid compression level invalid");
         }
 
         // @file