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Hello, the students in this lesson, we're going to learn more about features it was added in Java

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version nine.

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I'm talking about modules in Java.

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There we have really a lot of new things to learn modules, really powerful features that exist in Java

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platform.

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And if you want to become Java software engineer or get one of Oracle certifications, you have to be

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familiar with it.

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We'll start lesson from simple and general topics such as what models are and just talking about why

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we might need them to help you understand modules better.

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I will explain what goals we are trying to achieve by using them and what benefits we expect to get.

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We'll review different module types.

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After that, we'll learn module directives that we use in the module descriptor and common line options

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that might come in handy when you will work with multiple modules from Consult.

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And at the end of the lesson, we're going to create modular Hello World application, and I will show

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you how to configure it leaves and either you can work with this modular application from Eclipse.

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As you can see, we have really a lot of things to do.

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Let's start our lesson.

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Let's understand first what modules are.

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Module is a Nicklin named reusable group of related packages, as well as resources such as images and

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Xolo files and module.

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The specifying the modules name Xen Modules dependencies.

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These are the other modules.

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This module depends on zip packages.

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It explicitly makes available to other modules.

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All other packages in the module I implicitly unavailable to other modules, just services it offers,

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the services it consumes, but what other modules it allows?

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Reflection and General Module is a packaging mechanism that enables you to package a Java application

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or Java API as a separate Java module and general module is packaged as Modular Jar File and Java module

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can specify which of Java packages it contains.

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That should be visible to OSR Java modules, which he uses.

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This module and you have a module must also specify which OSI Jumo modules are required to do its job.

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In most single words, Java module is a package for packages that is super simplified, but hope this

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will help you to understand this concept.

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You can group packages into modules and to ensure encapsulation, you may control access to different

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packages within the module.

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Modularity as higher level of a nation above packages is a clear.

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Java Modules is a new feature in Java nine.

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We as a Java Platform Module System Z Java Platform Module System is also sometimes referred to as Java,

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Jigsaw or Project Jigsaw, depending on where you read.

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Jigsaw was internally used project name during development.

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Later, Jigsaw changed the name to Java Platform Module system.

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There is a juicer 376 Juicer stands for Java specification request.

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This is an actual description of proposed and final specification for the Java platform at any one time.

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There are numerous juicers movies with a review and approval process.

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In the Juicer 376, we can find list of goals of modular.

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Ryzen is a Java Sea platform, and one them such goals as a reliable configuration.

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Modularity provides mechanisms for explicitly declaring dependencies between modules in a manner that's

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recognized both at compile time and execution time.

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The system can work.

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Suzy's Dependencies commands a subset of all modules required to support your app from Gemini nine and

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forward Java applications must be packaged as Java Modules two zero four and application modules specifies

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what OSM modules Java API modules supporting modules.

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It uses zero for the Java virtual machine can check the whole module dependency graph from application

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module and four one one zero virtual machine starts up.

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If any required models are not found at startup, the Java Virtual Machine reports is a missing module

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and shuts down before Java nine Mason class.

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Just from a Mason Jar file, for example, would not be detected until the application actually tried

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to use Zoom Mason class.

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This would happen sometime at runtime dependent on one's application tried to use the missing class.

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Having missing modules reported at application startup time is a big advantage compared to its runtime

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when trying to use Zoom's Mojo Jar plus strong encapsulation zip packages in the module are accessible

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to OSM modules only use the module explicitly exports them.

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Even then, another module can't use those packages unless it explicitly states that it requires as

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other modules capabilities.

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This improves platform security because fewer classes accessible to potential attackers.

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You may find that considering modularity helps you come up with cleaner, more logical designs.

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Scalable Java Platform Robust is a Java platform was a monolith consisting of a massive number of packages,

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making it challenging to develop, maintain and evolve.

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It couldn't be easily subset.

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The platform is now one of the rise into ninety five modules.

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This number might change as Java evolves.

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You can create custom rom coms consisting of only modules you need for your apps was devices you are

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targeting.

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For example, if a device doesn't support graphical user interfaces, you could create a runtime that

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doesn't include xG.

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UI modules significantly reduces your runtime size before Java nine and the Java Platform Module system.

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You would have had to package all of the Java platform APIs with your job application because there

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was no official way of reliable checking.

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What crosses your Java application use?

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Since the job platform API eyes have grown quite large over the years, your application will get the

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large amount of Java classes included in its distribution, many of which your application would probably

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not be using.

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Greater platform integrity Before Java Non, it was possible to use many classes in the platform as

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it were not meant for use by and apps.

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Classes with strong encapsulation zones and channel API are truly encapsulated and hidden from apps

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using the platform.

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This can make migrating legacy code the Modularized Java non problematic.

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If your code depends on internal APIs, then use glossies make up the key from distributable big, then

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it needs to be.

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This can be a problem on small devices like mobile phones, Raspberry Pi, etc. was a Java platform

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modular system.

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You can now package your application was always a module of the Java Platform API that your application

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is actually using.

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This will result in small application distribution.

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Both improve performance.

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Gem uses various optimization techniques to improve application performance.

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GSR 376 indicates that these techniques are more effective when it's known in advance.

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Word types are located only in specific modules, and this was a great improvement for Java as a platform.

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Nowadays, questions about modules among many questions during different Oracle certifications.

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Let's talk now about different modules types.

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There are four types of modules in the new model system system modules.

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These other modules listed when we run Java.

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These modules Command Z, includes a Java Sea and JDK modules application modules.

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These models are what we usually want to build when we decide to use modules z unnamed and defined as

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a compile module info class file included in the assembled jar.

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Today, we are going to create our own module info file and see all examples automatic modules.

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We can include unofficial modules by an existing jar files to the module pass.

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The name of the module will be derived from the name of the jar.

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Automatic modules will have full access to every OSM module loaded by pass name tomorrow when a class

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or jar is loaded into the class bus.

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But no, the module bus.

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It's automatically added to the unnamed model.

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It's a catch all model to maintain backwards compatibility with previously written Java code.

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The unnamed, more new concept is similar to the default package.

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Therefore, it is not considered a real model but can be viewed as a default module.

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We can create multi-modal projects comprised of a main application and several library modules.

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We have to be careful, though, because we can only have one module per jar file.

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Let's see now what module descriptor is and what are the different directives that might be used in

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the module if a Java file, as we have discussed already, a module must provide a module descriptor

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metadata that specifies the modules, dependencies, zip packages the model makes available to other

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modules and more, and module descriptor is a compiled version of the module declaration that's defined

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in the file name module.

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Info jowar and the first scene that we need to do is to create a file was named Module Info and with

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Java extension.

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This file should be located in the source code directory.

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Each module declaration begins with the keyword module, followed by a unique module name and the module

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body enclosed in races like you see in that example.

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In general, module name follows the same naming rules as Java packages.

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However, you should not use underscores any module names or package names, class and these massive

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names, variable names, etc. from Gemini and Forward because Java wants to use underscore as reserved

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and easy to in the future.

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It is recommended to name a Java module is the same as the name of the root Java package contained in

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the module.

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If that is possible, because some of this might contain multiple packages is a module declarations,

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but it can be empty or may contain various module directives, including the requis experts provide

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space, etc. We are going to discuss each of these in a few minutes.

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As you'll see later, components and module declaration create is a model descriptor, which is stored

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in the file named Module Info, plus the Modules folder.

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On this slide, I will briefly introduce each module directive Zacchaeus only in module declarations

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and may be used as identifiers anywhere else in your code.

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Let's learn now directives.

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The first directives that we are given to them is requires.

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This module directive allows us to declare module dependencies, for example.

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In this case, my module has both a runtime and the compile time dependency on some module that you

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should refer by module name.

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Each module must explicitly state its dependencies.

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When Module eight requires Model B, Module A is set to read Module B and Module B is spread by Module

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A, the specified dependency on another module user requires and all public Typekit.

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Experts from a dependency are accessible by our module when we use this directive.

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Another important mention here is that it is not allowed to have separate dependencies between modules.

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In other words, if Module eight requires Module B, Module B can also require module a z module dependency

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graph must be an acyclic graph and thus a directive is a quasi static.

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We might write a lot of functions that pretty.

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Our internal state one another to log in module is present, but not every consumer of our level will

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want this functionality, and they don't want to include an extra log in library.

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In this case, we want to use an optional dependency.

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By using the request setting directive, we create a compile time only dependency.

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Now let's learn transitive directive.

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Imagine that we want to use third party library, and that library in turn has other dependencies.

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How we can make sure that any module that we are dependent on will bring its own dependencies to work

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properly.

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We can force any downstream consumers also to read our required dependencies, which requires transitive.

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Attractive, let's review exports DirecTV Now, as you already could understand, is a strong encapsulation

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was one of the main goal when Java Platform Module System has been introduced by default, and Model

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doesn't expose any of its API to other modules.

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Our code is significantly more secure if we don't expose our API to external users.

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But what if we created API that it should be used by different modules and we need to explicitly make

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it available for everyone?

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We use the experts directive to expose all public members of the named package.

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Please note that only the least the package itself is experts now support packages of the experts package

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experts.

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That means that even this package, in my example, contains a package named You Zens Akombe.

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My package name util package is not exported.

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Just because of parent package is to export the SAP package.

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Also, we must declare it explicitly in the module descriptor, and the one module is a singular package

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can only be exported by a single Java module at one time.

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In other words, you can't have two or more and more and use that export the same package in use at

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the same time.

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The Java Virtual Machine will come clean startup if you do having two modules export.

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The same package is also sometimes referred to as a split package by split package is meant that the

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total content classes of the package is split between the multiple modules.

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This is not allowed.

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In case we want to limit access to our API and expose it only to some packages XL, we have to use experts

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to direct it similar to the experts directive.

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We declare a package as experts, but we also list which models we are allowing to import this package

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as it requires.

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And here's how it looks like the next directive is users now use this Model Directive Force, a service

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used by this module, making the model a service consumer, a service services, an object of loss that

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implements the interface.

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So extensive apps are specified in the users directive.

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With this in mind, the services our model consumes with a users directive.

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No, just the last name we use.

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This is the interface for apps, loss of the service, the on the implementation class, because service

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in this context means and implementation of a specific interface or apps a gloss that can be consumed

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by OSI classes.

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But what is the difference between uses and requires the wrappers we might require and more uses?

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It provides a service we want to consume, but that service implements an interface from one of its

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transitive dependencies instead of forcing our module to require all transitive dependencies.

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Just in case we use the uses, Directive two adds the required interface to the module.

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POS is a career.

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We have discussed directives that consumes the services, but this also means that we have modules that

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provides services so a module can also be a service providers that other modules can consume, and we

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can ensure this voice provides with direction.

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We should write provides key words first and specifies the interface or abstract class name of our service

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is Let's see.

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What we have to do is to specify what specific implementation of our service we are going to provide

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was a help with directing.

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You provide the implementation class name that isn't implements.

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The interface or extents is an abstract class.

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The next important declarations that I'd like to show you opens and opens to.

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Let's learn this before December nine.

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Reflection could be used to learn about all types in the package and all members of it time even its

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private members, was the one that allows this capability on not.

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Thus, nothing was truly encapsulated like we have discussed already.

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The key motivation of the module system is strong, and cancellation by default and died in the module

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is not accessible to OSM modules unless it's a public type and you export its package.

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You expose all the packages you want to expose with Gemini.

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This also applies to reflection.

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For example, we can allow runtime only access to a package, so directive opened.

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Some package indicates that a specific package is public types and then nested public and protected

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types accessible to code in other modules at runtime only.

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Also, all the types in the specified package and all of the types members are accessible via reflection.

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Another example We can allow runtime only access the package by specific modules and opens to Model

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Directive.

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Like, for example, open package name to some list of modules indicates that specific packages, public

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types and then nascent public and protected types are accessible to code in the list of modules at runtime

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only.

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All of the types in the specified package and all of the types members are accessible via reflection

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to court in the specified modules.

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We have discussed already that one of the main goals of modules is strong encapsulation, and I believe

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that you watched the previous lesson and you're pretty familiar with reflection by this moment already.

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So you can understand that before June nine, it was possible to use a reflection to examine every type

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and the member in the package, even the private ones.

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Was through.

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Really encapsulated, which can open up all kinds of problems for developers of the libraries because

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Java nine enforce a strong encapsulation.

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We have to explicitly grant permission for OSM modules to reflect on our classes if we want to continue

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to allow full reflection as older versions of Java did, we can simply opens entire modules by using

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open direct before module name like you see on the slide.

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Does it make sense so far?

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And please always remember these in case you have any questions, please post them below this video

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and I will be happy to answer those.

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We have just learned directives that we can use in our modules in profile.

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The next step would be to learn how to build our modules.

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And before I show you examples of how to do that.

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Let me explain.

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Different command line options that we can use when we build Java modules, even despite the fact that

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later in our course, we are going to learn such views as Randall and May one and zero when you have

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support for building modules in Java.

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It's still valuable to know how to use modules.

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System forms a common plan will be used as a common line for our full example.

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I'm going to show you in a few minutes to help solidify how the entire system works in our minds.

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Module Pass.

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We use a module pass option to specify the module for us.

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This is a list of one on one directories that contain our modules athletes.

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Instead of relying on the module declaration file, we can use the command line equivalent of the requires

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directors and experts.

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Common Line replacement for the X Plus DirecTV and Opens replaces the open clause in the module declaration

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file adds modules adds is a list of modules into the default set of modules.

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These modules creates a list of all modules and their version strings by each module.

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Add or overwrite classes in modules.

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Illegal acts was values is permit over or do not use a relaxed encapsulation by showing a single global

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warning shows rewarding or fails with errors.

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The default is permit.

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Finally, we are done with the mini series piece.

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Let's continue learning modules with examples now.

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This would be our Hello World modular application.

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Thus, it would all be super complicated because the main goal right now is to make you understand key

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principles of modular application.

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The rest of the synths will be super easy to understand if you learned how everything works on the hood.

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So first of all, I want to say that for the sake of the demo, I created separate multi module project.

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I will share with you a link to it in attachments to this lesson.

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I have Food Project folder and I created the Modules folder.

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Apparently, this folder will contain different modules of my app.

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It is full of some main modules as a root source package.

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For example, it was a top level package of the module is compatibles greetings.

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Then I named the module in the same way.

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Note this is a full stops.

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These are modular root directory name.

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Z's full stops need to be easier because part of the module name Zen not to be interpreted as subdirectory

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POS dividers.

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Is it the.

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As you can see, I have two models here.

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Let me start from greeting Swan.

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It contains loss was named greetings and static mass insight that brings hello world to console.

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Each model should have Model E for file.

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Let's look at the model descriptor of this model.

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On the top, you can see model name.

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Basically, model name and name of the model for this should match and be expert package from this model.

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Experts directive is used was package name.

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Now creates a second model is the name of my second module is Compatibles App.

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This is the main module that uses greetings module.

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It has only one class was the main message where we use greetings class to invoke say hello mass pay

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attention.

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We also have the import statement here to import greetings class from another package.

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This module also has module descriptor.

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Let's look at it.

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Here we can see that this module requires my greetings module, and this is all of this agree because

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we are using class from greetings module in this one.

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Then the stand dependencies between these two modules, if he isn't great, if no, please press pause

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for a minute and think about it one more time.

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The next step that we need to do this to compile our models specially for that, I create a script that

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will compile all sources.

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It is located in the root directory and it is called Build this sage I use Linux shall come here, so

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pay attention to your transit script, either on Linux platforms or from Bosch on your Windows machine

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and do not use Windows Common Line to run this script.

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You know what Java commands?

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This is our Java compiler.

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After that, I pass the name of the output directly to specify where I want to put the compiled classes.

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The next thing I do, I need to pass module source plus option.

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This is different from the one I shared before.

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If you remember the interview module courses on a separate slot, there is a difference between module

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costs and module source boss.

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The component needs a distinction between the code it used to compile in module source, boss and location

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of compiled dependencies and libraries.

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Module boss does it make more sense now?

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I was here name of my folder with modules.

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After that, I used Show Command to find old files with Java Extension in Modules folder.

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Once my modular app is compiled, I can run it.

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I have another script for this.

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Is it a school run app or sage?

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Let's look at it in this script.

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You also see program that is familiar to you, Java.

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I am going to start Java Virtual Machine.

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I use option module POS to puzzle the reference to the compiled modules and after completion, all of

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them are stored in target output directory.

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You can see that all files here have class extension and even module info file is compiled into class

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file.

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Zen I specifies that most of the class it contains main message zip past consists of module name and

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full class name.

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So in this particular example, Compatibles Rules app is the model name and call it Bus App.

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App is a full class name.

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Is this clear?

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For the sake of the demo, I opened it March inside eclipse.

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I run build S.H. script first, and after that I run run apps, script and hindcast so we can see Hello

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World from the application.

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Can you see this?

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Congratulations to you with your first modular application.

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One more small comment here was the moment of recording this video.

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There is no single and proper way of using Eclipse to run multi-modal application.

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There might be some additional steps to configure multimodal application in eclipse.

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That's why, even on your work, most likely you would use common client to build and to run your complex

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enterprise application for the sake of convenience.

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You still can work in eclipse, but do you need to be prepared that sometimes you will see more errors?

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Is unusual because sometimes it is hard to conceive of all dependencies, not in the app, but in the

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creep's itself in order Eclipse would understand the clearly dependencies between all modules.

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Here's an example you can import two modules as separate projects and work in Java editor was Java files.

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But in app module, you may see error because Eclipse can't see dependency on another module.

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Since technically fruit loops, this is a separate project, and the groups allows only one module info

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file per project.

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In order to remove the error.

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Sometimes you may need to configure dependencies manually.

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If Eclipse didn't manage to configure everything automatically, for example, in my app module, I

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open built up submenu, configure builds bus and here on library staff.

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On the Module POS, I select Add Class Folder.

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Here I put checkbox next to the modules that they need in this one, namely Reding's module and press,

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OK.

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Now you wouldn't see any errors in the clips, but in case you have multiple modules and not all of

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them, I configure it automatically.

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This might take time during the configuration of your project very first time after these configuration

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steps.

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You may run even from Eclipse.

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Can you see this great since you have near Z simple syncs already?

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Let me show you how to add the service to our modular application.

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In my Goulding's module, I declare an interface was name service status log that contains only one

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massive print service that is slow.

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I have implementation of this interface.

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Is it the school default service status slogan for the sake of our demo and just brings text to console?

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Now, in my model info file, I need to declare that this module provides such service was a complete

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implementation.

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I use provides service directive for.

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This is the next logical step would be to consumes this service in my app module.

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I use uses directly for that and specify full class name of the interface.

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After that, in App G+ with the help of Service Loader from January to package I can load my service.

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I use load mass and quasi loss of the services that I need.

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Service loader is a terrible time.

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That's why it has iterate mass app that allows me to get a reference to the first service load.

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The object in the sequence handles a reference to the object.

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I can call print service that is massive.

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Let's now use our new brush to compile new sources one more time and run our app in so you can see that

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we successfully managed to invoke service message.

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That's all what I wanted to share with you in this lesson.

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Let's recap what we have learned in this lesson.

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In the lesson we have learned what general models are all seeing.

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Those are goals that we want to achieve and that that captures images.

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376.

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We have learned different more of those types of after that revealed details.

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Different command line options to work was more use and on real example, you saw how to create, build

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and run modular application.

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Together, we can simulate eclipse.

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The work was modular application form I.D. and the zenith of the lesson I explained to you how to provide

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and consume service in different modules.

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Thanks a lot for your attention.

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Have a great day and see you in the next lesson.