Fix #42 and it's a help for #32

pf4j/src/main/java/ro/fortsoft/pf4j/DefaultPluginManager.java

@@ -93,6 +93,7 @@ public class DefaultPluginManager implements PluginManager {
     private PluginFactory pluginFactory;
     private ExtensionFactory extensionFactory;
     private PluginStatusProvider pluginStatusProvider;
+    private DependencyResolver dependencyResolver;
 
     /**
      * The plugins repository.
@@ -297,6 +298,10 @@ public class DefaultPluginManager implements PluginManager {
      */
     @Override
     public PluginState stopPlugin(String pluginId) {
+        return stopPlugin(pluginId, true);
+    }
+
+    private PluginState stopPlugin(String pluginId, boolean stopDependents) {
     	if (!plugins.containsKey(pluginId)) {
     		throw new IllegalArgumentException(String.format("Unknown pluginId %s", pluginId));
     	}
@@ -315,9 +320,14 @@ public class DefaultPluginManager implements PluginManager {
             return pluginState;
         }
 
-    	for (PluginDependency dependency : pluginDescriptor.getDependencies()) {
+        if (stopDependents) {
-    		stopPlugin(dependency.getPluginId());
+            List<String> dependents = dependencyResolver.getDependents(pluginId);
-    	}
+            while (!dependents.isEmpty()) {
+                String dependent = dependents.remove(0);
+                stopPlugin(dependent, false);
+                dependents.addAll(dependencyResolver.getDependents(dependent));
+            }
+        }
 
     	try {
     		log.info("Stop plugin '{}:{}'", pluginDescriptor.getPluginId(), pluginDescriptor.getVersion());
@@ -813,7 +823,7 @@ public class DefaultPluginManager implements PluginManager {
 	}
 
 	private void resolveDependencies() throws PluginException {
-		DependencyResolver dependencyResolver = new DependencyResolver(unresolvedPlugins);
+		dependencyResolver = new DependencyResolver(unresolvedPlugins);
 		resolvedPlugins = dependencyResolver.getSortedPlugins();
         for (PluginWrapper pluginWrapper : resolvedPlugins) {
         	unresolvedPlugins.remove(pluginWrapper);

pf4j/src/main/java/ro/fortsoft/pf4j/DependencyResolver.java

@@ -28,7 +28,8 @@ class DependencyResolver {
 	private static final Logger log = LoggerFactory.getLogger(DependencyResolver.class);
 
     private List<PluginWrapper> plugins;
-    private DirectedGraph<String> graph;
+    private DirectedGraph<String> dependenciesGraph;
+    private DirectedGraph<String> dependentsGraph;
 
 	public DependencyResolver(List<PluginWrapper> plugins) {
 		this.plugins = plugins;
@@ -36,15 +37,23 @@ class DependencyResolver {
         initGraph();
 	}
 
+    public List<String> getDependecies(String pluginsId) {
+        return dependenciesGraph.getNeighbors(pluginsId);
+    }
+
+    public List<String> getDependents(String pluginsId) {
+        return dependentsGraph.getNeighbors(pluginsId);
+    }
+
 	/**
 	 * Get the list of plugins in dependency sorted order.
 	 */
 	public List<PluginWrapper> getSortedPlugins() throws PluginException {
-		log.debug("Graph: {}", graph);
+		log.debug("Graph: {}", dependenciesGraph);
-		List<String> pluginsId = graph.reverseTopologicalSort();
+		List<String> pluginsId = dependenciesGraph.reverseTopologicalSort();
 
 		if (pluginsId == null) {
-			throw new CyclicDependencyException("Cyclic dependencies !!!" + graph.toString());
+			throw new CyclicDependencyException("Cyclic dependencies !!!" + dependenciesGraph.toString());
 		}
 
 		log.debug("Plugins order: {}", pluginsId);
@@ -58,7 +67,8 @@ class DependencyResolver {
 
     private void initGraph() {
         // create graph
-        graph = new DirectedGraph<>();
+        dependenciesGraph = new DirectedGraph<>();
+        dependentsGraph = new DirectedGraph<>();
 
         // populate graph
         for (PluginWrapper pluginWrapper : plugins) {
@@ -67,10 +77,12 @@ class DependencyResolver {
             List<PluginDependency> dependencies = descriptor.getDependencies();
             if (!dependencies.isEmpty()) {
                 for (PluginDependency dependency : dependencies) {
-                    graph.addEdge(pluginId, dependency.getPluginId());
+                    dependenciesGraph.addEdge(pluginId, dependency.getPluginId());
+                    dependentsGraph.addEdge(dependency.getPluginId(), pluginId);
                 }
             } else {
-                graph.addVertex(pluginId);
+                dependenciesGraph.addVertex(pluginId);
+                dependentsGraph.addVertex(pluginId);
             }
         }
     }

pf4j/src/main/java/ro/fortsoft/pf4j/util/DirectedGraph.java

@@ -69,6 +69,13 @@ public class DirectedGraph<V> {
         neighbors.get(from).remove(to);
     }
 
+    public List<V> getNeighbors(V vertex) {
+        if (neighbors.containsKey(vertex)) {
+        	return new ArrayList<V>();
+        }
+        return neighbors.get(vertex);
+    }
+
     /**
      * Report (as a Map) the out-degree of each vertex.
      */