Java: Add PING command

java/client/src/main/java/glide/api/BaseClient.java

@@ -93,34 +93,40 @@ protected static CommandManager buildCommandManager(ChannelHandler channelHandle
     }
 
     /**
-     * Extracts the response from the Protobuf response and either throws an exception or returns the
-     * appropriate response as an <code>Object</code>.
+     * Extracts the value from a Redis response message and either throws an exception or returns the
+     * value as an object of type {@link T}. If <code>isNullable</code>, than also returns <code>null
+     * </code>.
      *
      * @param response Redis protobuf message
-     * @return Response <code>Object</code>
+     * @param classType Parameter {@link T} class type
+     * @param isNullable Accepts null values in the protobuf message
+     * @return Response as an object of type {@link T} or <code>null</code>
+     * @param <T> return type
+     * @throws RedisException on a type mismatch
      */
+    private <T> T handleRedisResponse(Class classType, boolean isNullable, Response response) {
+        Object value =
+                new BaseCommandResponseResolver(RedisValueResolver::valueFromPointer).apply(response);
+        if (isNullable && (value == null)) {
+            return null;
+        }
+        if (classType.isInstance(value)) {
+            return (T) value;
+        }
+        String className = value == null ? "null" : value.getClass().getSimpleName();
+        throw new RedisException(
+                "Unexpected return type from Redis: got "
+                        + className
+                        + " expected "
+                        + classType.toGenericString());
+    }
+
     protected Object handleObjectResponse(Response response) {
-        // convert protobuf response into Object
-        return new BaseCommandResponseResolver(RedisValueResolver::valueFromPointer).apply(response);
+        return handleRedisResponse(Object.class, false, response);
     }
 
-    /**
-     * Extracts the response value from the Redis response and either throws an exception or returns
-     * the value as a <code>String</code>.
-     *
-     * @param response Redis protobuf message
-     * @return Response as a <code>String</code>
-     * @throws RedisException if there's a type mismatch
-     */
     protected String handleStringResponse(Response response) {
-        Object value = handleObjectResponse(response);
-        if (value instanceof String || value == null) {
-            return (String) value;
-        }
-        throw new RedisException(
-                "Unexpected return type from Redis: got "
-                        + value.getClass().getSimpleName()
-                        + " expected String");
+        return handleRedisResponse(String.class, false, response);
     }
 
     @Override