Fix Object Factory to check class type when instantiating an object from class name

Author: iggarish

src/main/java/com/amazon/redshift/core/SocketFactoryFactory.java

@@ -38,7 +38,7 @@ public static SocketFactory getSocketFactory(Properties info) throws RedshiftExc
       return SocketFactory.getDefault();
     }
     try {
-      return (SocketFactory) ObjectFactory.instantiate(socketFactoryClassName, info, true,
+      return ObjectFactory.instantiate(SocketFactory.class, socketFactoryClassName, info, true,
           RedshiftProperty.SOCKET_FACTORY_ARG.get(info));
     } catch (Exception e) {
       throw new RedshiftException(
@@ -66,7 +66,7 @@ public static SSLSocketFactory getSslSocketFactory(Properties info) throws Redsh
       if (classname.equals(RedshiftConnectionImpl.NON_VALIDATING_SSL_FACTORY))
       		classname = NonValidatingFactory.class.getName();
 
-      return (SSLSocketFactory) ObjectFactory.instantiate(classname, info, true,
+      return  ObjectFactory.instantiate(SSLSocketFactory.class, classname, info, true,
           RedshiftProperty.SSL_FACTORY_ARG.get(info));
     } catch (Exception e) {
       throw new RedshiftException(

src/main/java/com/amazon/redshift/ssl/LibPQFactory.java

@@ -61,7 +61,7 @@ private CallbackHandler getCallbackHandler(Properties info) throws RedshiftExcep
     String sslpasswordcallback = RedshiftProperty.SSL_PASSWORD_CALLBACK.get(info);
     if (sslpasswordcallback != null) {
       try {
-        cbh = (CallbackHandler) ObjectFactory.instantiate(sslpasswordcallback, info, false, null);
+        cbh =  ObjectFactory.instantiate(CallbackHandler.class,sslpasswordcallback, info, false, null);
       } catch (Exception e) {
         throw new RedshiftException(
           GT.tr("The password callback class provided {0} could not be instantiated.",

src/main/java/com/amazon/redshift/ssl/MakeSSL.java

@@ -59,7 +59,7 @@ private static void verifyPeerName(RedshiftStream stream, Properties info, SSLSo
       sslhostnameverifier = "RedshiftjdbcHostnameVerifier";
     } else {
       try {
-        hvn = (HostnameVerifier) instantiate(sslhostnameverifier, info, false, null);
+        hvn = instantiate(HostnameVerifier.class, sslhostnameverifier, info, false, null);
       } catch (Exception e) {
         throw new RedshiftException(
             GT.tr("The HostnameVerifier class provided {0} could not be instantiated.",

src/main/java/com/amazon/redshift/util/ObjectFactory.java

@@ -34,13 +34,13 @@ public class ObjectFactory {
    * @throws IllegalAccessException if something goes wrong
    * @throws InvocationTargetException if something goes wrong
    */
-  public static Object instantiate(String classname, Properties info, boolean tryString,
+  public static <T> T instantiate(Class<T> expectedClass, String classname, Properties info, boolean tryString,
       String stringarg) throws ClassNotFoundException, SecurityException, NoSuchMethodException,
           IllegalArgumentException, InstantiationException, IllegalAccessException,
           InvocationTargetException {
     Object[] args = {info};
-    Constructor<?> ctor = null;
-    Class<?> cls = Class.forName(classname);
+    Constructor<? extends T> ctor = null;
+    Class<? extends T> cls = Class.forName(classname).asSubclass(expectedClass);    
     try {
       ctor = cls.getConstructor(Properties.class);
     } catch (NoSuchMethodException nsme) {