On Mon, Jun 12, 2017 at 8:18 PM, Sachin Jain <[email protected]>
wrote:
> Hi,
>
> I was going through the code of ConnectionFactory.createConnection in
> branch-1.3. Here is the method which is called upon eventually
>
> static Connection createConnection(final Configuration conf, final
> boolean managed,
> final ExecutorService pool, final User user)
> throws IOException {
> String className = conf.get(HConnection.HBASE_CLIENT_CONNECTION_IMPL,
> ConnectionManager.HConnectionImplementation.class.getName());
> Class<?> clazz = null;
> try {
> clazz = Class.forName(className);
> } catch (ClassNotFoundException e) {
> throw new IOException(e);
> }
> try {
> // Default HCM#HCI is not accessible; make it so before invoking.
> Constructor<?> constructor =
> clazz.getDeclaredConstructor(Configuration.class,
> boolean.class, ExecutorService.class, User.class);
> constructor.setAccessible(true);
> return (Connection) constructor.newInstance(conf, managed, pool, user);
> } catch (Exception e) {
> throw new IOException(e);
> }
> }
>
>
> It looks like we are instantiating HConnectionImplementaion via Reflection.
> I am a bit curious to understand why we used Reflection here and not
> instantiated it via just new operator.
>
>
This pattern is usual in place to allow plugging in alternative
implementations.
S
> Thanks
> -Sachin
>
