WEBVTT 00:00.080 --> 00:00.590 Hi everyone. 00:00.590 --> 00:01.190 Welcome back. 00:01.190 --> 00:02.570 So here is our design right. 00:02.600 --> 00:04.310 So we'll start with the payment gateway. 00:04.310 --> 00:10.550 So this payment gateway is going to be a sealed class which is going to have one function named make 00:10.550 --> 00:11.450 payment okay. 00:11.480 --> 00:16.640 So let's go ahead and start with that implementation I'm back in IntelliJ here I'm in the payment package. 00:16.640 --> 00:20.180 So in here I'm going to create a class named Payment gateway. 00:20.540 --> 00:27.110 So in this case create this is going to be payment gateway. 00:27.140 --> 00:27.710 There you go. 00:27.710 --> 00:29.030 So this is our class. 00:29.030 --> 00:33.350 And this class is going to be a sealed class and an abstract class. 00:33.350 --> 00:38.750 Because this is something like a contract where all the different implementations is going to provide 00:38.750 --> 00:40.160 their own implementation. 00:40.160 --> 00:45.890 So and then this is going to be using the permits class as we know the syntax by now, anytime you use 00:45.890 --> 00:50.450 a sealed keyword then you need to make sure you use a permits to allow. 00:50.480 --> 00:54.020 What are the different implementation your sealed class is going to support. 00:54.020 --> 00:59.210 So number one is if you go ahead and take a look at the design here we have debit card payment rewards 00:59.210 --> 01:01.500 card payment and the credit card payment. 01:01.500 --> 01:05.070 So the very first thing I'm going to create a class named debit card payment. 01:05.070 --> 01:08.370 So we can provide debit card payment over here. 01:08.400 --> 01:09.960 This class is not available yet. 01:09.960 --> 01:11.790 Let's go ahead and create this one. 01:11.790 --> 01:15.990 So create class and it's going to be part of the package named payment. 01:15.990 --> 01:17.220 And then press okay. 01:17.220 --> 01:21.240 So the debit card payment extends the payment gateway right. 01:21.240 --> 01:22.230 So that's a deal. 01:22.230 --> 01:27.600 And then anytime you create a subclass for a class what you need to do you need to provide one of the 01:27.600 --> 01:30.960 modifier which should be non-final or sealed. 01:30.960 --> 01:32.850 Or it can be final. 01:32.850 --> 01:38.160 So in this case I'm going to keep it final because I don't want any other class to extend this specific 01:38.160 --> 01:40.260 class which is debit card payment. 01:40.260 --> 01:42.360 So now let's go back to the payment gateway. 01:42.360 --> 01:44.070 All the compilation issues are gone. 01:44.070 --> 01:48.720 So now this abstract class is going to provide an abstract function okay. 01:48.750 --> 01:51.690 So in this case it's going to be public abstract. 01:51.690 --> 01:55.680 And then the function name is going to be make payment okay. 01:55.710 --> 02:00.770 And then this is going to accept the card information and the amount you want to make the payment for. 02:00.800 --> 02:02.690 So in this case it's going to be card. 02:02.690 --> 02:05.900 So we have this card as part of the domain class already. 02:05.930 --> 02:08.240 You can actually go ahead and import that. 02:08.240 --> 02:10.040 And the amount is going to be double. 02:10.070 --> 02:16.190 So in this case double amount I could have used Bigdecimal I just wanted to keep it double to ease our 02:16.190 --> 02:16.970 implementation. 02:16.970 --> 02:19.010 So what this function is going to return. 02:19.010 --> 02:22.040 This is going to return something called payment response. 02:22.040 --> 02:24.170 This enum is already part of the domain package. 02:24.170 --> 02:26.510 If you go here we have two different statuses. 02:26.540 --> 02:28.880 Number one is a success and number is a failure. 02:28.910 --> 02:34.130 Again one another thing to call out is that we are not going to be calling a real time payment gateway 02:34.130 --> 02:35.870 to get this payment completed. 02:35.900 --> 02:40.610 This is still going to be a static response, but the point that I'm trying to make here is that this 02:40.610 --> 02:46.100 lecture is going to provide you an approach to design and implement these kind of use cases. 02:46.220 --> 02:46.550 Okay. 02:46.580 --> 02:48.770 So in here we have this make payment. 02:48.800 --> 02:53.420 Now if we go to the debit card payment class you will be asked to provide an implementation. 02:53.420 --> 02:57.290 So what we will do we'll go ahead and implement that abstract function. 02:57.290 --> 02:58.460 So implement methods. 02:58.460 --> 02:59.330 So make payment. 02:59.330 --> 03:01.680 So this is what we need to implement. 03:02.010 --> 03:02.310 Okay. 03:02.340 --> 03:07.890 So as I mentioned we are actually not going to be calling any real time servers to acquire the payment. 03:07.890 --> 03:09.660 So I'm just going to print out here. 03:09.660 --> 03:12.180 So it's going to be a simple logger message. 03:12.180 --> 03:18.750 So in this case I'm going to provide acquire debit card payment for the amount. 03:18.750 --> 03:21.420 So we shouldn't be printing the card details at any cost. 03:21.420 --> 03:23.130 So I'm going to remove that away. 03:23.160 --> 03:23.760 There you go. 03:23.760 --> 03:28.980 And then the response is going to be payment response dot success. 03:28.980 --> 03:31.110 So it's always going to return success. 03:31.110 --> 03:37.320 But in reality if you have a payment gateway interacting with the actual bank based on what the banking 03:37.350 --> 03:42.150 application response, we will be able to get the real time status for that one. 03:42.150 --> 03:45.720 But with this implementation, it's going to be always success. 03:45.720 --> 03:49.140 So now this is the debit card payment implementation. 03:49.140 --> 03:53.850 So we need to provide the same implementation for the credit card and the rewards card too. 03:54.120 --> 03:54.510 Right. 03:54.510 --> 03:57.450 Because that's what our payment service design is. 03:57.450 --> 04:00.470 So we have the rewards card payment and then the debit card payment. 04:00.470 --> 04:06.020 So in here, in order to keep things simple, what we can do is we can actually copy this and then put 04:06.020 --> 04:06.800 it over here. 04:06.800 --> 04:11.240 And then we can call this one as credit card payment. 04:11.240 --> 04:16.970 So the credit card payment is going to be having its own implementation rights. 04:16.970 --> 04:19.280 But in this case we are just printing the value. 04:19.280 --> 04:23.690 So in this case let's go ahead and change this one to acquire credit card payment. 04:23.690 --> 04:29.720 But the payment gateway class complains about it because this credit card payment is not part of the 04:29.720 --> 04:31.370 permits class yet. 04:31.400 --> 04:31.730 Right. 04:31.760 --> 04:37.250 So in this case we need to add the credit card payment over here. 04:37.250 --> 04:40.190 So once you add that that particular error is resolved. 04:40.190 --> 04:45.170 So this function is going to just print the acquire credit card payment for the amount. 04:45.170 --> 04:48.980 And then the next thing is we need one for the rewards card payment. 04:48.980 --> 04:52.160 So let's go ahead and make a change over there. 04:52.160 --> 04:54.770 So this is going to be rewards card payment. 04:54.770 --> 04:57.800 And then the changes are going to be pretty much the same. 04:57.800 --> 05:02.130 So in here Acquire rewards card payment for the amount. 05:02.130 --> 05:05.550 And then you go ahead and add the rewards card over here. 05:05.580 --> 05:08.520 So in this case it's going to be rewards card payment. 05:08.580 --> 05:09.090 Okay. 05:09.120 --> 05:15.960 So now we have the implementations ready for all the different types of payment or checkout service. 05:15.960 --> 05:17.640 And the payment service supports. 05:17.640 --> 05:20.340 So if you go ahead and take a look at the reference of our design. 05:20.340 --> 05:25.530 So we have the payment gateway class ready, debit card payment ready, rewards card payment ready and 05:25.530 --> 05:26.700 credit card payment ready. 05:26.700 --> 05:30.930 The next step is we are going to implement a factory class based on the card type. 05:30.930 --> 05:35.640 It is going to give you an instance of this appropriate payment instance okay. 05:35.670 --> 05:37.890 So let's go ahead and create the factory class. 05:37.890 --> 05:41.670 So in this case what we are going to do we are going to create the payment factory. 05:41.670 --> 05:44.640 So in this case let's call payment factory. 05:44.670 --> 05:45.270 There you go. 05:45.270 --> 05:48.060 So this payment factory class is a regular class. 05:48.060 --> 05:50.550 And then this function is going to be a static function. 05:50.550 --> 05:52.800 So that is going to be a static function. 05:52.800 --> 05:56.940 And the name of this function is going to be payment gateway okay. 05:56.970 --> 05:59.480 So this is going to accept a card type. 05:59.510 --> 05:59.810 Okay. 05:59.840 --> 06:01.790 So in this case it's going to be card type. 06:01.790 --> 06:06.320 So based on the card type it is going to return the appropriate payment gateway. 06:06.320 --> 06:10.670 So what this return type is going to be it's going to be payment gateway. 06:10.700 --> 06:15.770 What we are implementing is a factory pattern just to call it out so that you know what we are going 06:15.770 --> 06:17.120 to be implementing. 06:17.120 --> 06:19.730 So in this case we can use the enhanced switch. 06:19.730 --> 06:19.970 Right. 06:19.970 --> 06:21.800 Because what we have is a card type. 06:21.800 --> 06:23.210 So the card type is credit. 06:23.210 --> 06:25.640 Then we need to return the credit card payment. 06:25.640 --> 06:29.420 If the card type is debit then we can return the debit card payment. 06:29.450 --> 06:33.290 If the card type is rewards then we can return the rewards card payment. 06:33.290 --> 06:36.050 So we can use the return here. 06:36.080 --> 06:39.350 Because switch is an expression by now you all know that. 06:39.350 --> 06:41.450 So in this case I'm going to pass the card type. 06:41.450 --> 06:42.440 So in the card type. 06:42.440 --> 06:44.600 So if the card is debit. 06:44.600 --> 06:50.690 So in this case we have a debit then it's going to return a new debit card payment okay. 06:50.690 --> 06:56.960 So if the card is credit then it's going to return a new credit card payment okay. 06:56.990 --> 07:02.880 Now if the card is rewards, then in this case it's going to be new rewards card payment. 07:02.910 --> 07:04.830 Okay then end this with semi. 07:04.980 --> 07:07.890 So there is no default block required for this one. 07:07.890 --> 07:10.740 The reason being what we are dealing with is a enum, right? 07:10.740 --> 07:16.380 So if you have a specific enum which just has three different types, then you just need to provide 07:16.380 --> 07:19.770 the implementation for all those supported values. 07:19.770 --> 07:24.210 So this is the exhaustive nature of the enhanced switch I was referring to. 07:24.240 --> 07:28.200 But in this case there is a possibility the card type can still be null. 07:28.200 --> 07:30.630 So we can have a case null. 07:30.630 --> 07:36.090 In the case of this one we can throw an illegal argument exception, and then we can actually provide 07:36.090 --> 07:40.650 the message as card type null not supported okay. 07:40.680 --> 07:42.360 So this is still possible. 07:42.360 --> 07:47.370 It's better to have a null implementation to handle any kind of null pointer exceptions. 07:47.370 --> 07:50.310 So this is our payment factory implementation. 07:50.310 --> 07:54.570 So the payment service is going to be interacting with the payment factory. 07:54.570 --> 07:59.660 So we have completed the payment gateway and the implementation of each and every car type, and then 07:59.660 --> 08:01.640 the payment factor is also completed. 08:01.670 --> 08:05.690 Now let's go ahead and integrate this flow into the payment service. 08:05.720 --> 08:10.700 If you go to the payment service currently, it doesn't deal with any of the classes that we created 08:10.700 --> 08:11.000 yet. 08:11.000 --> 08:12.950 So the very first thing is what we are going to do. 08:12.980 --> 08:17.090 We are going to call payment factory, dot payment gateway. 08:17.090 --> 08:18.740 And then what do we pass to this one. 08:18.740 --> 08:23.030 So in this case we pass the order details dot card dot card type. 08:23.030 --> 08:27.170 So when you pass this what you are going to get is a payment gateway implementation. 08:27.200 --> 08:27.380 Right. 08:27.410 --> 08:30.260 So in this case it's going to be payment gateway. 08:30.290 --> 08:31.010 There you go. 08:31.040 --> 08:32.720 And in here what we are going to do. 08:32.720 --> 08:34.910 So we are going to be returning. 08:34.940 --> 08:36.920 So we can comment this one for now. 08:37.430 --> 08:40.100 Payment gateway dot make payment. 08:40.100 --> 08:42.500 And then you provide the card and the amount. 08:42.530 --> 08:42.710 Right. 08:42.710 --> 08:44.900 So that's what this make payment function accepts. 08:44.900 --> 08:46.970 It accepts a card and the final amount. 08:47.000 --> 08:51.680 So in this case we can get those information from the order details domain class. 08:51.680 --> 08:56.450 So dot card and then order details dot final amount. 08:56.480 --> 08:57.080 There you go. 08:57.080 --> 08:59.280 And then what this is going to respond with. 08:59.310 --> 09:01.800 This is going to respond with a payment response. 09:01.800 --> 09:07.410 So in the in our case, it's always going to be the success because we have some static implementations 09:07.410 --> 09:10.920 of credit card payment, debit card payment and rewards card payment. 09:10.920 --> 09:14.370 All those are returning the payment success okay. 09:14.400 --> 09:19.500 So now if you go to the caller of this function, so the checkout service, once it makes a call based 09:19.500 --> 09:24.540 on the type of the card that's been part of the order details, the appropriate implementation will 09:24.540 --> 09:26.790 be invoked and the response will be sent. 09:27.000 --> 09:30.120 Okay, let me quickly recap what we have done so far. 09:30.120 --> 09:35.430 So anytime the checkout service gets this order details to the checkout order function, it's going 09:35.430 --> 09:37.500 to make a call to the payment service. 09:37.500 --> 09:40.140 And then it's going to call the payment gateway. 09:40.140 --> 09:45.660 So the payment gateway based on the type of the card it's going to provide the appropriate implementation. 09:45.660 --> 09:51.090 So this type of implementation is called a factory pattern because this class acts as a factory of different 09:51.090 --> 09:53.730 implementations based on the input that you provide. 09:53.730 --> 09:58.080 It takes one implementation from the factory and sends that as a response. 09:58.080 --> 10:00.380 So once it's sent to the caller. 10:00.380 --> 10:05.000 So in this case, once the payment gateway is sent which has the appropriate implementation, then we 10:05.000 --> 10:06.260 make a call to the make payment. 10:06.260 --> 10:08.330 And it might go to one of the implementations. 10:08.330 --> 10:12.050 It could be a debit card payment credit card payment or rewards card payment. 10:12.050 --> 10:14.930 And then the appropriate response will be sent back. 10:14.960 --> 10:15.320 Okay. 10:15.350 --> 10:19.850 Now what we are going to do, we are going to write a simple test case to test this behavior. 10:19.850 --> 10:21.980 So there is a test case already available. 10:21.980 --> 10:28.070 So in this case if you go to the checkout service there is a checkout service test class you might be 10:28.100 --> 10:30.140 able to find in the test package. 10:30.140 --> 10:30.830 There you go. 10:30.830 --> 10:33.500 And then in here we can write the test case for this one. 10:33.500 --> 10:38.180 So we have this order details static function based on the card type that you pass. 10:38.210 --> 10:41.300 It's going to randomly create an order details object. 10:41.300 --> 10:43.280 And then it's going to give that as a response. 10:43.280 --> 10:47.540 So what we are going to do is we are going to create a parameterized test over here. 10:47.540 --> 10:50.240 So in this case let's go ahead and add the parameterized test. 10:50.240 --> 10:54.740 And I'm going to add the name equal to checkout for cart type. 10:54.740 --> 10:58.300 And then we are going to be getting the cart type from a enum source. 10:58.300 --> 11:04.570 So in this case it's going to be at enum source and then provide the card type value. 11:04.600 --> 11:06.370 So in this case card Typeclass. 11:06.370 --> 11:11.500 If you provide this information this value will be passed as a input to this test function. 11:11.530 --> 11:15.190 So in this case we can actually provide this value in this format. 11:15.220 --> 11:21.310 What this is going to do is this is going to print the card type value which represents each enum value. 11:21.310 --> 11:25.210 Because if you go and take a look at the card type, we have three different values, right. 11:25.210 --> 11:30.550 We have the credit, debit and rewards, which means this particular test case will be executed for 11:30.550 --> 11:32.020 three different inputs. 11:32.020 --> 11:33.760 And then I'm going to write the function. 11:33.790 --> 11:35.440 It's going to be void checkout. 11:35.440 --> 11:37.960 And then this is where the card type will be passed. 11:37.990 --> 11:40.420 So in this case card type will be passed. 11:40.420 --> 11:44.440 And the source for the card type is coming from this enum source. 11:44.470 --> 11:44.890 Okay. 11:44.920 --> 11:48.880 So the very first thing is we pass the card type to the order detail function. 11:48.880 --> 11:51.190 And this is going to return the order details. 11:51.190 --> 11:55.600 In this case it's going to be order details. 11:55.600 --> 12:00.150 And then we are going to be calling the checkout service, so checkout service is already available 12:00.150 --> 12:02.190 as an instance in this particular class. 12:02.190 --> 12:07.920 And then we call the checkout service dot checkout order and then pass the order details over here. 12:08.310 --> 12:13.050 And if you take a look at the checkout service we have an instance of payment service already passed 12:13.050 --> 12:13.410 to it. 12:13.440 --> 12:13.890 Right. 12:13.890 --> 12:17.760 Because that's needed for the whole orchestration of the flow to start. 12:17.760 --> 12:22.170 So when we call the checkout order from here, what this is going to do, this is going to make the 12:22.170 --> 12:24.180 call to the make payment function. 12:24.180 --> 12:25.470 This doesn't have to be V2. 12:25.500 --> 12:31.740 What I'm going to do I'm going to change this function name to be make payment okay. 12:31.770 --> 12:37.200 And then it makes a call to the gateway gets the appropriate implementation based on the card type. 12:37.200 --> 12:40.170 And then we make the call to the payment function okay. 12:40.200 --> 12:42.090 So now let's go back to the test case. 12:42.090 --> 12:45.750 So from the test case this is always going to give you the success response. 12:45.750 --> 12:48.000 In this case we can actually call this response. 12:48.000 --> 12:49.740 And then we can call Assertequals. 12:49.770 --> 12:54.210 It's going to be checkout status dot success comma response. 12:54.210 --> 12:59.340 So the response is always going to be success rate because we are not making any real time call. 12:59.370 --> 13:01.470 The response is always going to be static. 13:01.470 --> 13:03.810 So now let's go ahead and execute this test case. 13:03.810 --> 13:08.370 So this test case is going to call each and every card type. 13:08.370 --> 13:10.050 So in this case it starts with the credit. 13:10.050 --> 13:15.570 And you can see right in the logger we have the acquire credit card payment for the amount 99. 13:15.570 --> 13:18.810 And we have for the debit we have the acquired debit card payment. 13:18.810 --> 13:22.050 This means the debit card implementation is invoked right. 13:22.080 --> 13:25.020 Because that's what this particular logger is coming from. 13:25.020 --> 13:26.610 And then the next one is the rewards. 13:26.610 --> 13:30.540 So rewards is again it's coming from the reward card implementation. 13:30.840 --> 13:31.290 There we go. 13:31.290 --> 13:34.140 So the payment factory class acts as an entry point. 13:34.140 --> 13:38.040 So based on the card type it's going to return you the appropriate instance. 13:38.040 --> 13:40.620 And that particular instance will be invoked. 13:41.010 --> 13:47.160 So we wrote our test case that actually test all the behavior that we have expected to work. 13:47.190 --> 13:50.850 I hope you all have a pretty good idea about how this whole implementation works. 13:50.850 --> 13:53.850 If you have any questions, please go ahead and write it in Q&A. 13:53.880 --> 13:55.110 I would be happy to help. 13:55.110 --> 13:56.520 This marks the end of this lecture. 13:56.520 --> 13:57.540 Thank you for watching.