1 00:00:02,120 --> 00:00:08,590 In the last lecture, we learned how to look into the lambda function and we saw the object being passed 2 00:00:08,590 --> 00:00:13,120 to that function, that request object with all the request metadata. 3 00:00:13,120 --> 00:00:16,400 Now as I said at the end of the last lecture, I don't like that, 4 00:00:16,430 --> 00:00:21,400 I like my lambda functions to be clean and to only work with the data I need. 5 00:00:21,400 --> 00:00:28,300 I think the lambda functions shouldn't need to parse any incoming event and extract exactly what it 6 00:00:28,300 --> 00:00:28,800 needs if 7 00:00:28,840 --> 00:00:33,110 it doesn't need 90% of that data, instead 8 00:00:33,160 --> 00:00:35,540 that should be the job of the API Gateway. 9 00:00:35,740 --> 00:00:36,240 There, 10 00:00:36,250 --> 00:00:41,560 you should ensure that you only pass to your action, lambda in this case, 11 00:00:41,560 --> 00:00:43,660 what this action needs. 12 00:00:44,140 --> 00:00:50,110 So I will go back to integration request and uncheck this lambda proxy integration, confirm and confirm 13 00:00:50,110 --> 00:00:56,730 again and we're back to the old world thereafter with the body mapping template. 14 00:00:56,740 --> 00:01:02,930 Now again, since no template is selected, the whole request body is forwarded to lambda. 15 00:01:02,950 --> 00:01:16,920 So now if we reword this to simply login the event and we test this again by passing an object where 16 00:01:16,920 --> 00:01:25,020 we have name, Max, I'll omit the age here, we see that we get this back and this is back to the state we were at. 17 00:01:25,470 --> 00:01:25,800 Now 18 00:01:25,830 --> 00:01:33,510 I was mentioning a more elegant way of extracting data and only passing data to lambda it needs, 19 00:01:33,510 --> 00:01:37,770 this way uses body mapping templates, 20 00:01:37,770 --> 00:01:41,130 let me change the structure of the request body. 21 00:01:41,400 --> 00:01:51,990 Let's say we actually have a person data property here which is another object which then in turn holds 22 00:01:51,990 --> 00:01:53,450 that name. 23 00:01:53,460 --> 00:02:01,590 So this is the data we send and we maybe also have the age here, 28. This is the data we send to lambda, if we 24 00:02:01,590 --> 00:02:04,220 do send it, we get this returned. 25 00:02:04,710 --> 00:02:09,980 Now in the lambda function, let's say I don't just want to return this event data, 26 00:02:10,290 --> 00:02:14,960 instead what I want to do here is I log it, 27 00:02:15,210 --> 00:02:20,850 then I want to retrieve the age and I want to retrieve age on the event. 28 00:02:20,850 --> 00:02:29,680 However right now, I would have to use person data age, right because age is a property 29 00:02:29,730 --> 00:02:35,730 on this person data object here. I also get the name even though the lambda function is not interested 30 00:02:35,730 --> 00:02:36,740 in that 31 00:02:36,810 --> 00:02:45,510 and here, I could return age times two. Now if I save this and I click test again, we get back 56 which is twice 32 00:02:46,650 --> 00:02:47,350 28. 33 00:02:47,430 --> 00:02:48,890 So that makes sense 34 00:02:49,050 --> 00:02:54,100 but again, the lambda function has to care about the structure of the data it receives. 35 00:02:54,240 --> 00:02:59,280 It would be much better if the lambda function could simply access age on the event because it knows that 36 00:02:59,280 --> 00:03:05,720 there will be an age property and only age property because that is all this lambda function needs 37 00:03:06,060 --> 00:03:12,180 and this is where body mapping templates enter the stage. In the integration request and response, 38 00:03:12,240 --> 00:03:18,780 we can use them to map in the case of request, the data we pass to the action and in the case of response, 39 00:03:19,020 --> 00:03:21,410 data we get out of that action. 40 00:03:21,420 --> 00:03:28,170 So here integration request, we can scroll down and first of all switch this to when there are no templates 41 00:03:28,170 --> 00:03:29,390 defined. 42 00:03:29,400 --> 00:03:34,550 Now let's add a template, I'll name it application/json 43 00:03:34,710 --> 00:03:40,410 and with that, the request body will not be forwarded by default anymore but this template will be used, 44 00:03:40,860 --> 00:03:46,200 though just as for the response if this template is empty, it will still forward the request 45 00:03:46,500 --> 00:03:55,650 but if I simply set this to an empty object here and hit save and we now go back to testing this, let 46 00:03:55,650 --> 00:03:56,230 me hit 47 00:03:56,280 --> 00:04:08,120 test here, you see we get back null and we can check our cloud watch logs here, the latest stream to see 48 00:04:08,690 --> 00:04:12,070 that indeed, we get an empty object here, 49 00:04:12,230 --> 00:04:15,260 this is what we'll log the console here. 50 00:04:15,260 --> 00:04:21,440 The reason for this is that in our template, we transform the incoming data and simply pass on an 51 00:04:21,470 --> 00:04:24,360 empty object to our action, to lambda. 52 00:04:24,430 --> 00:04:29,050 Not super useful obviously but just showing what we can do with that. 53 00:04:29,100 --> 00:04:32,390 Now typically of course, we don't overwrite the data with an empty object, 54 00:04:32,390 --> 00:04:38,510 instead what we want to do here is do something more useful and use the powerful body mapping template 55 00:04:38,570 --> 00:04:40,150 language 56 00:04:40,430 --> 00:04:42,560 AWS API Gateway provides us with.