WEBVTT 00:00.230 --> 00:03.980 Hey, everyone, and welcome back to the Knowledge Portal Video series. 00:04.010 --> 00:11.260 Now, continuing our journey with the get method will be speaking about conditional get in today's lecture. 00:11.270 --> 00:14.180 So let's go ahead and understand more about this. 00:15.930 --> 00:20.340 Now conditional get method is used to fetch information. 00:20.370 --> 00:23.190 However, with a specific condition. 00:23.340 --> 00:32.520 So in this example we have a get method which is get slash sample dot HTML for the http 1.1 protocol. 00:32.550 --> 00:40.710 Host is Dexter labs in and a condition which is specified over here is that if modified since. 00:40.710 --> 00:45.150 So this is the header and there is a date and time associated. 00:45.180 --> 00:56.040 So you have if modified since Saturday, 18th October 2017 at evening, 7:00 and 43 minutes and 31 seconds 00:56.040 --> 00:57.210 of GMT time. 00:57.750 --> 01:06.840 So what this basically says that get me this file only and only if it is modified after this specific 01:06.840 --> 01:07.410 time. 01:07.740 --> 01:11.880 If it is not modified that, then do not really need the file. 01:11.880 --> 01:15.940 I just need the file if it is modified or if it is updated. 01:16.600 --> 01:20.320 So this is the basic about conditional get. 01:20.350 --> 01:26.320 Let's get back to our labs and we'll understand this specific value. 01:27.010 --> 01:40.750 So when you do a curl on Dexter labs dot in slash sample dot HTML this time I'll do a hyphen I so that 01:40.750 --> 01:42.490 we can see the response headers. 01:44.010 --> 01:52.410 And within the response header there is a very important header called last modified and followed. 01:52.560 --> 02:02.820 The value associated with this header is Wednesday, 18th October 2017 at 5:00, 19 minutes and 43 seconds 02:02.820 --> 02:03.300 GMT. 02:03.540 --> 02:14.430 So this response header basically tells us on what was the last time this file sample dot HTML was modified. 02:14.640 --> 02:24.630 Now this is a very important header because if a browser is or if a user is trying to load this file 02:24.630 --> 02:30.150 again and again, and if the file is not modified, what a browser can do is browser can store this 02:30.150 --> 02:35.490 file in cache and it can only supply the newer version. 02:35.520 --> 02:38.610 If this last modified date has been updated. 02:38.610 --> 02:41.670 We'll be discussing this in the upcoming lectures. 02:42.030 --> 02:44.560 But for the time being, let's do one thing. 02:45.370 --> 02:54.700 Let's do a curl and I'll say Dexter dot P labs dot n slash sample dot HTML. 02:55.000 --> 02:59.110 So this time I'll get a response, which is of two lines. 02:59.440 --> 03:05.050 This is sample sample file and it is specifically designed for get request. 03:05.080 --> 03:11.740 Now we'll add an additional header with hyphen hyphen header. 03:13.600 --> 03:21.370 And this time I'll add a header if modified since. 03:25.030 --> 03:29.710 And we'll put a value which is present over here. 03:32.080 --> 03:35.770 I'll paste it and I'll press enter. 03:36.610 --> 03:40.810 Now here you will see you did not really get any response. 03:40.840 --> 03:47.920 Now, the reason why you did not get response is because the file is not modified after this specific 03:47.920 --> 03:56.230 time that we have mentioned over here, if the file gets modified after this date and time which is 03:56.230 --> 04:01.180 specified, then the response will be received. 04:01.210 --> 04:06.880 So let's try one thing instead of 519. 04:07.000 --> 04:11.950 I'll say 518 So just a minute back and I'll press enter. 04:11.950 --> 04:15.160 And now you'll see I got the response back. 04:15.340 --> 04:23.710 Now, the reason why I got response is because the file was modified after this specific time interval 04:23.710 --> 04:27.820 that we have been writing in our header file. 04:28.690 --> 04:36.340 So if you look into the headers, let's do one thing. 04:38.230 --> 04:45.910 I'll put hyphen I so in hyphen I you are getting the response because file was actually modified at 04:45.910 --> 04:46.990 519. 04:47.140 --> 04:55.630 Now if I do 519 back here again this time instead of 200. 04:55.630 --> 04:59.560 Okay, you will get 304 not modified. 04:59.590 --> 05:08.710 So the web server is saying to the client that the file has not been modified after this specific amount 05:08.710 --> 05:12.790 of time and thus the response is not received. 05:12.790 --> 05:21.610 The contents of this file is being not received, and this specific conditional plays a very important 05:21.610 --> 05:25.240 role during the caching process of browsers. 05:25.360 --> 05:29.750 So this is the basic about the conditional get. 05:29.770 --> 05:33.510 I hope you got what a condition basically means. 05:33.520 --> 05:37.690 So this specific condition is something that we are specifying. 05:37.690 --> 05:41.420 Like if this condition is met, then only send us the file. 05:41.440 --> 05:44.750 If condition is not met, do not send me the file. 05:44.770 --> 05:49.780 So this is what the high level overview of the conditional get really means. 05:49.810 --> 05:52.450 So this is it about this lecture. 05:52.630 --> 05:54.790 I hope this has been informative for you. 05:54.820 --> 06:00.490 Again, if you have any doubts suggestions, feel free to connect us at Twitter, Facebook or LinkedIn 06:00.490 --> 06:04.030 or mail us at instructors at the Rate Labs dot n. 06:04.060 --> 06:05.260 Thanks for watching.