[Issue-81] Gracefully handle missing dependencies. (#82)

* [ISSUE-81] catch NoClassDefFoundError errors and bubble up appropriately

* [ISSUE-81] Update changelog

* Add missing changelog entries

* [ISSUE-81] Add more helpful exception error msg

Author: Crim

CHANGELOG.md

@@ -3,7 +3,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## 1.0.5 (UNRELEASED)
-- [Issue#75](https://github.com/SourceLabOrg/kafka-webview/issues/75) Bugfix Add Jackson serializer that falls back to using toString() when consuming entries from Kafka. 
+- [Issue#75](https://github.com/SourceLabOrg/kafka-webview/issues/75) Bugfix Add Jackson serializer that falls back to using toString() when consuming entries from Kafka.
+- [Issue#72](https://github.com/SourceLabOrg/kafka-webview/issues/72) Bugfix User role input not displayed when creating new user.
+- [Issue#81](https://github.com/SourceLabOrg/kafka-webview/issues/81) Bugfix Handle NoClassDefFoundError exceptions gracefully.
+- [Issue#74](https://github.com/SourceLabOrg/kafka-webview/issues/74) Improvement UI Tweak to display large number of partitions in datatable views.
+- [Issue#71](https://github.com/SourceLabOrg/kafka-webview/issues/71) Improvement Topics sorted in select boxes. 
 
 ## 1.0.4 (06/11/2018)
 - Update NPM dependencies for [CVE-2017-18214](https://nvd.nist.gov/vuln/detail/CVE-2017-18214).

kafka-webview-ui/src/main/java/org/sourcelab/kafka/webview/ui/manager/plugin/PluginFactory.java

@@ -122,7 +122,14 @@ public T getPlugin(final String jarName, final String classpath) throws LoaderEx
         final Class<? extends T> dClass = getPluginClass(jarName, classpath);
         try {
             return dClass.newInstance();
-        } catch (InstantiationException | IllegalAccessException e) {
+        } catch (final NoClassDefFoundError e) {
+            // Typically this happens if the uploaded JAR references some dependency that was
+            // not package in the JAR.  Attempt to provide a useful error msg.
+            final String errorMsg = e.getMessage()
+                + " - Does your JAR include all of its required dependencies? "
+                + "See https://github.com/SourceLabOrg/kafka-webview-examples#packaging-a-jar";
+            throw new LoaderException(errorMsg, e);
+        } catch (final InstantiationException | IllegalAccessException e) {
             throw new LoaderException(e.getMessage(), e);
         }
     }

kafka-webview-ui/src/main/java/org/sourcelab/kafka/webview/ui/manager/plugin/exception/LoaderException.java

@@ -31,7 +31,7 @@ public class LoaderException extends Exception {
     /**
      * Constructor.
      */
-    public LoaderException(final String message, final Exception cause) {
+    public LoaderException(final String message, final Throwable cause) {
         super(message, cause);
     }