Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 1 1 00:00:00,889 --> 00:00:03,038 In this video, we're gonna discuss 2 2 00:00:03,038 --> 00:00:06,038 the bean scopes available in Spring. 3 3 00:00:07,715 --> 00:00:09,968 So what exactly are scopes? 4 4 00:00:09,968 --> 00:00:12,979 Well, a scope refers to the lifecycle of a bean, 5 5 00:00:12,979 --> 00:00:16,108 for example, it tells you how long the bean will live, 6 6 00:00:16,108 --> 00:00:18,533 how many instances will be created 7 7 00:00:18,533 --> 00:00:22,700 and also how is the bean shared in the Spring environment? 8 8 00:00:24,865 --> 00:00:27,697 So the default scope for a bean is singleton, 9 9 00:00:27,697 --> 00:00:30,211 so here's an example here of just some bean code, 10 10 00:00:30,211 --> 00:00:33,402 that we had earlier and we didn't explicitly give a scope, 11 11 00:00:33,402 --> 00:00:37,112 so by default, the scope is singleton. 12 12 00:00:37,112 --> 00:00:39,124 But now you're probably wondering, 13 13 00:00:39,124 --> 00:00:41,050 well, what exactly is a singleton? (laughs) 14 14 00:00:41,050 --> 00:00:43,529 we know it's a default scope, but what is it? 15 15 00:00:43,529 --> 00:00:46,035 Well, for a singleton, the Spring Container 16 16 00:00:46,035 --> 00:00:50,534 creates only one instance of the bean, it's cached in memory 17 17 00:00:50,534 --> 00:00:52,766 and then all requests for that bean 18 18 00:00:52,766 --> 00:00:56,543 will return a shared reference to the same bean, 19 19 00:00:56,543 --> 00:00:59,017 so the end result is that there is only one bean 20 20 00:00:59,017 --> 00:01:01,267 and everyone will share it. 21 21 00:01:03,579 --> 00:01:06,639 Here's a nice diagram to kind of show you this example. 22 22 00:01:06,639 --> 00:01:09,361 In this example, we have theCoach 23 23 00:01:09,361 --> 00:01:11,323 equals context.getBean myCoach 24 24 00:01:11,323 --> 00:01:13,544 and it'll give you a reference to like a TrackCoach, 25 25 00:01:13,544 --> 00:01:16,836 that you have defined and then later on in the code, 26 26 00:01:16,836 --> 00:01:18,724 if you would also do a similar thing, 27 27 00:01:18,724 --> 00:01:22,504 saying context.getBean myCoach, the same bean id, 28 28 00:01:22,504 --> 00:01:26,830 then it'll basically give you a reference to the same bean. 29 29 00:01:26,830 --> 00:01:28,923 We have these two object references here 30 30 00:01:28,923 --> 00:01:32,144 and they point to the same area of memory 31 31 00:01:32,144 --> 00:01:35,221 or they point to the same bean, 32 32 00:01:35,221 --> 00:01:37,748 so again, Spring makes use of a singleton, 33 33 00:01:37,748 --> 00:01:41,262 it'll create only one bean and then share it 34 34 00:01:41,262 --> 00:01:43,382 for everyone who requests that bean, 35 35 00:01:43,382 --> 00:01:45,288 so the singleton scope is default 36 36 00:01:45,288 --> 00:01:48,277 and the best use case for this is for a stateless bean, 37 37 00:01:48,277 --> 00:01:51,860 where you don't need to maintain any state. 38 38 00:01:52,851 --> 00:01:55,382 You can explicitly specify the bean scope, 39 39 00:01:55,382 --> 00:01:57,161 I mean, by now you know that by default, 40 40 00:01:57,161 --> 00:01:58,666 you have the singleton scope, 41 41 00:01:58,666 --> 00:02:00,416 but if you want to explicitly specify, 42 42 00:02:00,416 --> 00:02:02,720 then you make use of the scope attribute, 43 43 00:02:02,720 --> 00:02:04,631 so you say scope equals singleton 44 44 00:02:04,631 --> 00:02:05,940 and that'll make it a singleton bean 45 45 00:02:05,940 --> 00:02:08,993 and that's kind of the preferred approach 46 46 00:02:08,993 --> 00:02:13,801 to minimize the number of beans, that are created. 47 47 00:02:13,801 --> 00:02:16,239 But now, there are additional Spring bean scopes, 48 48 00:02:16,239 --> 00:02:17,621 that you can make use of. 49 49 00:02:17,621 --> 00:02:19,876 We've already covered singleton, 50 50 00:02:19,876 --> 00:02:21,606 there's also the prototype scope, 51 51 00:02:21,606 --> 00:02:24,386 which creates a new bean instance for each container request 52 52 00:02:24,386 --> 00:02:26,484 and we'll see examples of that coming up 53 53 00:02:26,484 --> 00:02:31,124 and we'll also use that as a demo in the video coming up, 54 54 00:02:31,124 --> 00:02:32,872 then the next three items here, 55 55 00:02:32,872 --> 00:02:34,877 request, session and global-session, 56 56 00:02:34,877 --> 00:02:37,357 these scopes are only used in a web environment, 57 57 00:02:37,357 --> 00:02:40,951 so request is for a given web request, 58 58 00:02:40,951 --> 00:02:44,234 session is for a HTTP web session, for like session tracking 59 59 00:02:44,234 --> 00:02:46,150 for like maybe a shopping cart or something 60 60 00:02:46,150 --> 00:02:49,488 and then global-session is scope application-wide, 61 61 00:02:49,488 --> 00:02:51,268 but we'll talk more about these later, 62 62 00:02:51,268 --> 00:02:53,520 when we get into the Spring MVC section, 63 63 00:02:53,520 --> 00:02:57,818 but for now, we'll simply focus on singleton and prototype. 64 64 00:02:57,818 --> 00:03:00,129 So here's an example of using prototype scope, 65 65 00:03:00,129 --> 00:03:02,872 so again, remember, prototype scope, 66 66 00:03:02,872 --> 00:03:05,495 a new object is created for each request, 67 67 00:03:05,495 --> 00:03:09,310 so in this example here, I have my bean id of myCoach 68 68 00:03:09,310 --> 00:03:12,047 and I have scope equals prototype, 69 69 00:03:12,047 --> 00:03:13,547 so that means that every time 70 70 00:03:13,547 --> 00:03:16,544 I make a request for this myCoach, 71 71 00:03:16,544 --> 00:03:19,877 they'll create a new instance each time. 72 72 00:03:21,012 --> 00:03:23,368 So, a nice little diagram here. 73 73 00:03:23,368 --> 00:03:24,901 So the line of code at the top, 74 74 00:03:24,901 --> 00:03:27,447 theCoach equals context.getBean myCoach, 75 75 00:03:27,447 --> 00:03:29,713 it'll create a new instance of that bean, 76 76 00:03:29,713 --> 00:03:32,949 I'll get a reference to it and then a similar thing here, 77 77 00:03:32,949 --> 00:03:37,116 when I say alphaCoach equals context.getBean myCoach, 78 78 00:03:37,963 --> 00:03:39,826 it'll create a new object for you 79 79 00:03:39,826 --> 00:03:42,743 and you'll have your own reference. 80 80 00:03:43,637 --> 00:03:46,407 So the prototype scope is good for keeping track 81 81 00:03:46,407 --> 00:03:49,160 of stateful data, so again, whenever you see prototype, 82 82 00:03:49,160 --> 00:03:52,781 just think of the new keyword, it's gonna create a new bean 83 83 00:03:52,781 --> 00:03:57,418 for each request for that component or that object. 84 84 00:03:57,418 --> 00:03:59,750 Alright, so this is some really good stuff. 85 85 00:03:59,750 --> 00:04:01,117 Let's go ahead and move forward, 86 86 00:04:01,117 --> 00:04:03,390 in the next videos, we're gonna dive into Eclipse 87 87 00:04:03,390 --> 00:04:04,766 and we'll actually write some code, 88 88 00:04:04,766 --> 00:04:07,036 that'll make use of the singleton scope 89 89 00:04:07,036 --> 00:04:08,614 and the prototype scope, 90 90 00:04:08,614 --> 00:04:11,165 so you can see everything in action. 91 91 00:04:11,165 --> 00:04:14,582 Alrighty, I'll see you in the next video. 8101