Fixed the bug "Getting content from reloaded node(Node whose state have been saved and re-loaded from file) NullPointerException".

Wrote a test to show getting content from reloaded node

src/kademlia/Kademlia.java

@@ -185,6 +185,7 @@ public class Kademlia
          */
         din = new DataInputStream(new FileInputStream(getStateStorageFolderName(ownerId, iconfig) + File.separator + "dht.kns"));
         DHT idht = new JsonDHTSerializer().read(din);
+        idht.setConfiguration(iconfig);
 
         return new Kademlia(ownerId, inode, ikad.getPort(), idht, iconfig);
     }

src/kademlia/dht/DHT.java

@@ -15,6 +15,7 @@ import kademlia.exceptions.ContentExistException;
 import kademlia.exceptions.ContentNotFoundException;
 import kademlia.node.NodeId;
 import kademlia.serializer.JsonSerializer;
+import kademlia.serializer.KadSerializer;
 
 /**
  * The main Distributed Hash Table class that manages the entire DHT
@@ -26,16 +27,11 @@ public class DHT
 {
 
     private transient StorageEntryManager entriesManager;
-    private final transient JsonSerializer<KadContent> contentSerializer;
-    private final transient KadConfiguration config;
+    private transient KadSerializer<KadContent> contentSerializer = null;
+    private transient KadConfiguration config;
 
     private final String ownerId;
 
-    
-    {
-        contentSerializer = new JsonSerializer<>();
-    }
-
     public DHT(String ownerId, KadConfiguration config)
     {
         this.ownerId = ownerId;
@@ -51,6 +47,31 @@ public class DHT
         entriesManager = new StorageEntryManager();
     }
 
+    /**
+     * Set a new configuration. Mainly used when we restore the DHT state from a file
+     *
+     * @param con The new configuration file
+     */
+    public void setConfiguration(KadConfiguration con)
+    {
+        this.config = con;
+    }
+
+    /**
+     * Creates a new Serializer or returns an existing serializer
+     *
+     * @return The new ContentSerializer
+     */
+    public KadSerializer<KadContent> getContentSerializer()
+    {
+        if (null == contentSerializer)
+        {
+            contentSerializer = new JsonSerializer<>();
+        }
+
+        return contentSerializer;
+    }
+
     /**
      * Handle storing content locally
      *
@@ -68,7 +89,7 @@ public class DHT
             /* Now we store the content locally in a file */
             String contentStorageFolder = this.getContentStorageFolderName(content.getKey());
             DataOutputStream dout = new DataOutputStream(new FileOutputStream(contentStorageFolder + File.separator + sEntry.hashCode() + ".kct"));
-            contentSerializer.write(content, dout);
+            getContentSerializer().write(content, dout);
         }
         catch (ContentExistException e)
         {
@@ -88,7 +109,7 @@ public class DHT
     {
         String folder = this.getContentStorageFolderName(key);
         DataInputStream in = new DataInputStream(new FileInputStream(folder + File.separator + hashCode + ".kct"));
-        return contentSerializer.read(in);
+        return getContentSerializer().read(in);
     }
 
     /**

src/kademlia/tests/SaveStateTest2.java

@@ -0,0 +1,79 @@
+package kademlia.tests;
+
+import java.util.List;
+import kademlia.Kademlia;
+import kademlia.core.GetParameter;
+import kademlia.dht.KadContent;
+import kademlia.node.NodeId;
+
+/**
+ * Testing the save and retrieve state operations.
+ * Here we also try to look for content on a restored node
+ *
+ * @author Joshua Kissoon
+ * @since 20140309
+ */
+public class SaveStateTest2
+{
+
+    public SaveStateTest2()
+    {
+        try
+        {
+            /* Setting up 2 Kad networks */
+            Kademlia kad1 = new Kademlia("JoshuaK", new NodeId("ASF45678947584567463"), 12049);
+            Kademlia kad2 = new Kademlia("Crystal", new NodeId("ASF45678947584567464"), 4585);
+
+            /* Connecting 2 to 1 */
+            System.out.println("Connecting Nodes 1 & 2");
+            kad2.bootstrap(kad1.getNode());
+            System.out.println(kad1);
+            System.out.println(kad2);
+
+            DHTContentImpl c;
+            synchronized (this)
+            {
+                System.out.println("\n\n\n\nSTORING CONTENT 1\n\n\n\n");
+                c = new DHTContentImpl(kad2.getOwnerId(), "Some Data");
+                System.out.println(c);
+                kad1.putLocally(c);
+            }
+
+            System.out.println(kad1);
+            System.out.println(kad2);
+
+            /* Shutting down kad1 and restarting it */
+            System.out.println("\n\n\nShutting down Kad 1 instance");
+            kad1.shutdown(true);
+
+            System.out.println("\n\n\nReloading Kad instance from file");
+            kad1 = Kademlia.loadFromFile("JoshuaK");
+            kad1.bootstrap(kad2.getNode());
+            System.out.println(kad2);
+
+            /* Trying to get a content stored on the restored node */
+            GetParameter gp = new GetParameter(c.getKey(), kad2.getOwnerId(), c.getType());
+            List<KadContent> content = kad2.get(gp, 1);
+
+            if (!content.isEmpty())
+            {
+                DHTContentImpl cc = (DHTContentImpl) content.get(0);
+                System.out.println("Content received: " + cc);
+            }
+            else
+            {
+                System.out.println("No Content found");
+            }
+        }
+
+        catch (Exception e)
+        {
+            e.printStackTrace();
+        }
+    }
+
+    public static void main(String[] args)
+    {
+        new SaveStateTest2();
+    }
+}