WEBVTT 00:00.050 --> 00:00.590 Hi everyone. 00:00.590 --> 00:01.400 Welcome back. 00:01.400 --> 00:09.110 In this lecture I'll introduce you to the new concept named Java Platform Module System or Jpms or Project 00:09.140 --> 00:09.710 Jigsaw. 00:09.710 --> 00:15.890 So these are the different terms you might hear if you are learning about Java Platform module system. 00:15.890 --> 00:21.410 So this lecture is going to be a theory lecture where I'm going to explain about why this was introduced 00:21.410 --> 00:23.270 in Java nine. 00:23.300 --> 00:27.530 As I said, this concept got introduced in Java nine. 00:27.530 --> 00:34.190 But the fundamental idea of Jpms is to package and deploy your applications in a better way. 00:34.190 --> 00:38.420 That's a concept of using the Jpms in your application. 00:38.420 --> 00:44.120 So the next basic question that might be running in your head is that why was this needed in the Java 00:44.150 --> 00:45.680 ecosystem in the first place? 00:45.680 --> 00:49.040 The very first reason is to modularize the JDK. 00:49.040 --> 00:50.450 So what do I mean by that? 00:50.450 --> 00:58.880 So until Java eight we used to have the jar file which holds all the necessary runtime libraries or 00:58.880 --> 01:01.070 classes to run a Java applications. 01:01.070 --> 01:03.950 But in most cases we don't need everything. 01:03.950 --> 01:07.340 For example, let's say you are building a RESTful API, okay? 01:07.370 --> 01:09.950 Which is very common in today's software development. 01:09.950 --> 01:15.410 You don't need the classes under the applet package to be loaded into the JVM, right? 01:15.410 --> 01:18.770 We don't even reference anything when you are building a RESTful API. 01:18.800 --> 01:26.330 So by modularizing the JDK, the app can control on adding just the modules the app requires. 01:26.330 --> 01:32.330 So that's the advantage with modularizing the JDK, so that you get to pick and choose what you want. 01:32.360 --> 01:37.760 We will code and explore how to do this as we go further in this section, let me quickly show you how 01:37.760 --> 01:40.070 the modularized JDK looks like. 01:40.070 --> 01:46.850 So on the left I have the reference or representation of how the Jar file looks like until Java eight. 01:46.850 --> 01:52.490 From Java nine, any code that you are running beyond Java nine uses the modular approach. 01:52.490 --> 02:00.140 So in this case, the whole JDK is structured as modules, and each module holds a specific set of code 02:00.140 --> 02:02.630 that the application can import into it. 02:02.660 --> 02:07.220 You might have many questions on your head on how would I achieve that from a coding perspective? 02:07.250 --> 02:12.200 You just got to wait until we get to the coding lectures will be exploring all these concepts. 02:12.230 --> 02:17.510 Another important reason for introducing modularity is to enable secure coding. 02:17.510 --> 02:23.180 By default, public is too open, which means any class that has a public modifier in it. 02:23.180 --> 02:29.360 Then any other class can actually access or extend another class and then start using it. 02:29.360 --> 02:35.720 But with the modules, we have a new restrictive controls to restrict access to certain internal classes. 02:35.720 --> 02:39.680 You can also define which classes are visible to the outside world. 02:39.680 --> 02:43.250 Which classes are going to be just visible to the module. 02:43.250 --> 02:48.770 For example, we can actually control the packages in a library that can be exposed to the client. 02:48.770 --> 02:53.330 This means we can make certain packages invisible to the users of the library. 02:53.810 --> 02:59.690 And another reason is in today's world, any class can be accessed at runtime using reflection, and 02:59.690 --> 03:01.430 then we can modify the behavior. 03:01.430 --> 03:06.230 But using modules but using modules, we can restrict reflection during runtime. 03:06.230 --> 03:10.190 Now let's discuss about the benefits of Jvms or modules. 03:10.190 --> 03:15.620 We are going to have smaller jar file, which basically means we are going to have a reduced memory 03:15.620 --> 03:19.940 footprint and possibly we will have an improved application startup time. 03:19.940 --> 03:26.000 We will still have a clear separation of boundaries with introduction of modules where each module owns 03:26.000 --> 03:27.860 certain responsibilities. 03:27.920 --> 03:34.670 We will also have stricter access control, which is a new way of restricting access to certain internal 03:34.670 --> 03:37.850 classes, which was never intended to be used by others. 03:37.850 --> 03:42.440 So with this information in place, let's quickly take a look at the modules that we have been using 03:42.440 --> 03:44.390 already so far without our knowledge. 03:44.390 --> 03:49.910 I'm going to go back to IntelliJ and then show you those modules, and there is a hierarchy of how those 03:49.910 --> 03:51.020 modules are connected. 03:51.020 --> 03:52.790 I will show that information too. 03:52.820 --> 03:54.500 So let's go back to IntelliJ. 03:54.530 --> 03:55.550 So in the IntelliJ. 03:55.580 --> 03:57.710 So this is a code base we have been working so far. 03:57.740 --> 03:59.450 Let me close all the tabs here. 03:59.480 --> 04:00.410 There you go. 04:00.440 --> 04:05.720 And in here if you minimize all the projects you will notice something called external libraries. 04:05.720 --> 04:07.550 Over here if you expand this one. 04:07.550 --> 04:10.310 And if you expand the JDK that we have been using so far. 04:10.310 --> 04:13.610 So in here you see right, we have been using these modules. 04:13.610 --> 04:18.860 So if you take a look at it, we have a Java based Java compiler desktop logging. 04:18.860 --> 04:21.590 You have many different modules that are part of it. 04:21.590 --> 04:27.140 So whatever that starts with Java Dot, those are specifically used by the application code. 04:27.140 --> 04:32.390 And JDK is something which will be used by the Java platform, which means the Java runtime. 04:32.420 --> 04:32.780 Okay. 04:32.810 --> 04:35.690 So let's quickly take a look at what we have in the base package. 04:35.690 --> 04:41.240 If you open the base package, this is where all the Java.lang class files and all those things sit 04:41.270 --> 04:41.570 actually. 04:41.570 --> 04:46.910 So if you expand Java and if you expand and if you can expand Lang to see whether the string classes 04:46.910 --> 04:50.180 are there, if you go a little bit down, you may be able to find the string class. 04:50.180 --> 04:52.460 So string class is something which is very popular. 04:52.460 --> 04:54.860 So we normally use it on a day to day basis. 04:54.890 --> 04:55.190 Right. 04:55.220 --> 05:01.010 So all these classes which are the base requirement to run a Java application are part of this Java 05:01.340 --> 05:02.840 base module. 05:02.870 --> 05:04.430 And then you have other modules too. 05:04.430 --> 05:07.940 So you have the SQL one as a separate module altogether. 05:07.940 --> 05:10.880 And you have XML one which is a separate module altogether. 05:10.880 --> 05:15.290 So in this case, let's say you're building a code which doesn't require any kind of DB interaction 05:15.290 --> 05:16.250 or XML. 05:16.250 --> 05:21.380 Then you can ignore those libraries and just use the base, which should take care of automatically 05:21.380 --> 05:24.800 loading the dependencies for you so that you can build your application. 05:24.800 --> 05:28.970 So if you are looking for a complete view of how these modules are connected. 05:28.970 --> 05:30.650 So I'm going to go back to the browser. 05:30.650 --> 05:35.780 So in the browser so you can see this specific link I'll be sharing this link and I'll attach it to 05:35.810 --> 05:36.320 this lecture. 05:36.320 --> 05:38.450 So in here if you click on this one. 05:38.450 --> 05:42.980 So it will actually show you the complete view of how the different modules are connected. 05:42.980 --> 05:45.200 But number one is the Java base. 05:45.200 --> 05:50.870 So all the other modules that are part of the Java platform module system actually reference base. 05:50.870 --> 05:54.470 As you can see all these modules use it Java.net dot HTTP. 05:54.500 --> 05:55.850 It also uses base. 05:55.850 --> 05:59.450 And if you think about the SQL one it requires XML. 05:59.450 --> 06:02.720 And then that again indirectly depends upon base. 06:02.720 --> 06:06.140 So this is the hierarchy tree if you're interested in learning about it. 06:06.140 --> 06:11.180 But from a developer perspective you don't need to know each and every module and how it's connected. 06:11.180 --> 06:13.610 It's based on what application you build. 06:13.640 --> 06:18.290 You'll be getting recommendations from the IntelliJ itself when you start coding these concepts. 06:18.530 --> 06:19.940 I hope the explanation is clear. 06:19.940 --> 06:25.070 With this information, we will start building some modular applications using Java Platform Module 06:25.070 --> 06:25.460 system. 06:25.460 --> 06:26.840 This marks the end of this lecture. 06:26.840 --> 06:27.800 Thank you for watching.