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Building Applications with Spring 5 and Kotlin

Chapter 1. Starting Up

Welcome! You are starting a long trip into the unknown: the unknown kingdom of Spring Framework. Luckily, you have the right guide and great companions! You have us! In this book, you will discover what Spring Framework is and how powerful it can be in modern web application development. We will teach you all about workflow with the framework and guide you through a real-world application example. Get ready to learn!

This chapter will cover the following points:

Defining your mission
Separating code into independent entities
Planning your environment
Preparing the working environment
Setting up a Git repository

Separating code into independent entities

Before we start with the implementation, we will separate our code into independent entities. Each entity will cover a single responsibility and therefore will be implemented when we cover a certain Spring functionality.

We will start with the main classes that will represent the data we will actually handle: Notes and TODOs. Then we will describe user-related stuff: the users themselves and the roles we plan to assign to them. Later, when we actually implement most of them, we will introduce some new entities to cover additional responsibilities. This will be explained in Chapter 3, Building Your First Spring RESTful Service with Kotlin.

Describing entities

The main entities that we will use and that will hold the data are Notes and TODOs. We can consider each of them as an entry that will be stored and that has common attributes:

ID: Universally Unique IDentifier (UUID) String
Title: String
Message: String
Location: String value that represents serialized Location class into JSON.

Here are all the entities that we use:

Note: The Note entity will represent Notes in the system with all common attributes.
TODO: The TODO entity will represent TODOs in the system with all common attributes and timestamps for a scheduled time.
User: The User entity will be completely independent of the main data entities. The user will represent the user and all the attributes that the user of the system can have, including assigned roles. The user will have the following attributes:
- ID: UUID String
- Email: String
- Password: String
- First name: String
- Last name: String
- Roles: String
Enabled: Boolean representing whether the user has activated the account or whether it has been activated by the user from a higher user hierarchy
Created on: Long representing UTC timestamp when the user was created
Updated on: Long representing UTC timestamp when the user was updated

In later stages, we can introduce additional attributes if there is a need. For now, we will stick to the most important ones we just described.

Preparing the working environment

Finally, it's time to prepare our working environment. We will prepare all the software needed to develop and run our application. For this process, we will need the following:

Git
JDK
IDE
Spring 5
Postman

For a proper development machine, you can use any computer having, for example, an i5 processor (or more powerful) with at least 8 GB of RAM. These are the main characteristics. You can do your development on Microsoft Windows, Linux, or macOS. All the development mentioned in this book was done on macOS Sierra (version 10.12.6).

Installing Git

We will use Git as our version control system. To install it, follow the procedure for your OS. We will provide guidance for the following:

Microsoft Windows
Linux (Debian, Ubuntu, Fedora, and raw source code)
macOS

Microsoft Windows

Here are the steps for installing Git on Microsoft Windows:

Download Git for Microsoft Windows from the following location: https://git-for-windows.github.io/.
Start the installer and follow the instructions.
Open the Command Prompt.
Configure Git with the following commands:

$ git config --global user.name "Your Name"
$ git config --global user.email "[email protected]"

macOS

To install Git on macOS, we recommend that you install Xcode with command-line tools from the App Store. Then, open Terminal and verify the Git version:

$ git -version 
git version 2.7.0 (Apple Git-66)

Linux

Follow the installation steps for your distribution.

Debian and Ubuntu

The following are the steps to install Git on Debian and Ubuntu:

Open Terminal.
Use the following commands to start the installation:

$ sudo apt-get update 
$ sudo apt-get install git

Verify the installation:

$ git -version

The output should be something like the following:

git version 2.9.2

Configure Git with the following commands:

$ git config --global user.name "Your Name" 
$ git config --global user.email "[email protected]"

Fedora

The following are the steps to install Git on Fedora:

Open Terminal.
Depending on your Fedora version, use YUM or DNF to install Git as follows:

$ sudo dnf install git 
//or
$ sudo yum install git

Verify the installation:

$ git -version

The output should be something like the following:

git version 2.9.2

Configure Git with the following commands:

$ git config --global user.name "Your Name"
$ git config --global user.email "[email protected]"

Building Git from the source code

If you prefer to build your stuff from source code, you can do the same with Git.

Debian and Ubuntu

To build from source, you need some dependencies installed:

Open Terminal and install the following dependencies:

$ sudo apt-get update
$ sudo apt-get install libcurl4-gnutls-dev libexpat1-dev gettext libz-dev libssl-dev asciidoc xmlto docbook2x

Navigate to your preferred directory.
Clone the Git source code as follows:

$ git clone https://git.kernel.org/pub/scm/git/git.git

Build Git as follows:

$ make all doc info prefix=/usr
$ sudo make install install-doc install-html install-info install-man prefix=/usr

Note

We installed Git in the /usr directory. Use a different filesystem location if you prefer.

Fedora

The following are the steps to build from the source code:

As was the case with Debian and Ubuntu, install the dependencies needed to build Git as follows:

$ sudo dnf install curl-devel expat-devel gettext-devel openssl-devel perl-devel zlib-devel asciidoc xmlto docbook2X

If you have an older version of Fedora, run the following commands:

$ sudo yum install epel-release
$ sudo yum install curl-devel expat-devel gettext-devel openssl-devel perl-devel zlib-devel asciidoc xmlto docbook2X

Symlink docbook2X to the filename that the Git build expects:

$ sudo ln -s /usr/bin/db2x_docbook2texi /usr/bin/docbook2x-texi

Navigate to your preferred directory.
Clone the Git source code as follows:

$git clone https://git.kernel.org/pub/scm/git/git.git

Finally, build Git:

$ make all doc prefix=/usr
$ sudo make install install-doc install-html install-man prefix=/usr

Note

We installed Git in the /usr directory. Use a different filesystem location if you prefer.

Congratulations! You have installed the Git version control system on your machine! You are ready to create repositories that will keep your code. We will do this in Setting up a Git repository section.

Installing JDK

As you already know, we will use Kotlin as our primary development language. However, we need Java installed on our system since Kotlin is executed on JVM. Open the Java JDK home page and chose the proper installation depending on the version of your OS: http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html.

The following platforms are supported:

Linux ARM 32 Hard Float ABI
Linux ARM 64 Hard Float ABI
Linux x86
Linux x86
Linux x64
Linux x64
macOS X
Solaris SPARC 64-bit
Solaris SPARC 64-bit
Solaris x64
Solaris x64
Windows x86
Windows x64

Follow the instructions depending on your OS version.

Microsoft Windows

The following are the steps to install JDK in Microsoft Windows:

Download the proper executable for your version of Microsoft Windows
Execute the downloaded file
Follow the instructions

Linux

Here are the steps to install JDK in Linux:

Download the proper RPM Package Manager (RPM) installation package for your platform.
Open Terminal and install the package:

$ rpm -ihv package_you_downloaded.rpm

Verify you have installed the Java version:

$ java -version

macOS

The following are the steps to install JDK in macOS:

Download the dmg file for your macOS.
Double-click on the dmg file to run it.
Double-click on the PKG icon to launch the installation.
Follow the installation instructions. Enter your system credentials if asked.
Verify that the Java version from Terminal:

$ java -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

Congratulations! Java is up and running! The next thing we are going to do is set up our IDE.

Installing the IDE

We chose IntelliJ IDEA as our IDE. Unfortunately, IDEA is not free. It is commercial software. You can buy a license or use IntelliJ IDEA Community Edition, Eclipse, or NetBeans to get it running. Follow the installation instructions for your specific OS.

Microsoft Windows

The following are the steps to install IDEA in Microsoft Windows:

Download IntelliJ IDEA from the JetBrains website: https://www.jetbrains.com/idea/download/#section=windows.
Launch setup by executing the file you downloaded.
Follow the installation instructions.

Linux

The following are the steps to install IDEA in Linux:

Download IntelliJ IDEA from the JetBrains website: https://www.jetbrains.com/idea/download/#section=linux.
Unpack the ideaIC.gz or ideaIU.gz file you have downloaded.
Switch to the directory where you extracted IntelliJ IDEA.
Execute the idea.sh script.

macOS

The following are the steps to install IDEA in macOS:

Download IntelliJ IDEA from the JetBrains website: https://www.jetbrains.com/idea/download/#section=macos.
Double-click the ideaIC.dmg or ideaIU.dmg file you have downloaded to mount the macOS disk image.
Copy IntelliJ IDEA to the Applications folder.

Starting IntelliJ for the first time

You have installed IntelliJ; now it is time for the first run. You will be asked to do some configuring. Don't worry, everything is simple and easy. Just follow the instructions:

Launch IntelliJ and wait until the Complete Installation dialog appears. Choose Don't import settings and continue by clicking on OK.

Next, you will be prompted to select the UI theme. You can choose between the default theme and the Darcula theme. We recommend that you use the Darcula theme:

In the next section, disable any plugins that are not required:

In the next step, you are prompted to download additional plugins:

Finally, you can start the project! The setup is complete, as shown in the following screenshot:

Installing Spring 5

Before installing or running Spring 5, we need to install Kotlin, since this is our primary programming language for the project:

Open IntelliJ IDEA and choose Configure | Plugins, as shown in the following screenshot:

In the search field, type Kotlin:

Click on the Install JetBrains plugin... button.

From the list that appears, choose Kotlin.
If you do not already have Kotlin installed, you will see a green Install button. Click on it, otherwise click on the Update button, as shown in the following screenshot:

Wait until the installation or update process completes:

When the installation is finished, click on the Restart IntelliJ IDEA button:

If the Restart IntelliJ IDEA button does not restart your IDE, do it yourself manually.

Your IDE is ready for development. It is time to finally set up Spring 5! You can use Spring in the same way as any standard Java library. Simply include the appropriate Spring library files in your classpath. Spring does not require any special tool integration, so you can use any IDE or text editor! As you already know, we will stick to IntelliJ IDEA. You can run and debug Spring applications as you would any other Java application.

Spring can be used through Maven or Gradle. It is up to you to choose which suits you better. We will use Gradle in our development but we will give examples of Maven too.

Maven installation

The recommended way to get started using Spring Framework in your project is with a dependency management system. Take a look at the following Maven example:

<dependencies> 
    <dependency> 
        <groupId>org.springframework</groupId> 
        <artifactId>spring-context</artifactId> 
        <version>5.0.0.RC4</version> 
    </dependency> 
</dependencies><repositories> 
    <repository> 
        <id>spring-milestones</id> 
        <name>Spring Milestones</name> 
        <url>https://repo.spring.io/libs-milestone</url> 
        <snapshots> 
            <enabled>false</enabled> 
        </snapshots>      
    </repository>  
</repositories>

Gradle installation

Gradle installation requires less code, as the following snippet shows:

repositories { 
    maven { 
        url 'https://repo.spring.io/libs-milestone' 
    } 
}  
dependencies { 
    compile 'org.springframework:spring-context:5.0.0.RC4' 
 
}

Installing Postman

To try out our API calls, we will need Postman. Postman is a complete toolchain for API development. Postman is designed from the ground up to support the API developer. It offers us an intuitive user interface to send requests, save responses, add tests, and create workflows.

To get Postman, open https://www.getpostman.com/postman and choose your OS.

Microsoft Windows installation

The following are the steps to install Postman in Microsoft Windows:

Download the setup file
Run the installer
Follow the setup instructions

Linux installation

To simplify the installation process, we recommend that you install it through the Google Chrome store. Search for Postman and install it:

macOS installation

Once you have downloaded the Postman-archived application, extract it, then drag the file to the Applications folder. Double-click on Postman to open the application.

Postman is installed. Run it and take a look at its UI. We will not go into details on how to use it. It is enough to play a bit. Most of the options are self-explanatory. Enjoy!

The following screenshot shows the Postman application running on macOS:

Setting up a Git repository

We have installed the IDE and Spring Framework. It is time to start working on our project. We will develop a REST application API for Notes and TODOs. This is a tool that everybody needs. We will give it a name: Journaler API. Journaler API will be a REST application capable of creating Notes and TODOs with reminders. Many different applications, such as mobile ones, will be synced to our backend instance running this REST application.

The first step in development is initializing a Git repository. Git will be our code versioning system. It is up to you to decide whether you will use GitHub, BitBucket, or something else for your remote Git instance. Create your remote repository and keep its URL ready along with your credentials. So, let's start!

The following are the steps to set up Git:

Go into the directory containing the project.
Execute the following command:

$ git init .

The console output will be something like the following:

Initialized empty Git repository in <directory_you_choose/.git>

We have initialized the repository. Now let's add the first file by executing the following command:

$ vi notes.txt

Note

Here we are using vi editor to edit notes.txt. If you are familiar with some other editor, use that.

Populate notes.txt with some content and save it.
To add all of the relevant files, execute the following commands:

$ git add .
$ git commit -m "Journaler API: First commit"

The console output will be something like the following:

[master (root-commit) 5e98ea4] Journaler API: First commit
 
1 file changed, 1 insertion(+)
 
create mode 100644 notes.txt

Use the remote Git repository URL that you have prepared previously with credentials, and execute the following command:

$ git remote add origin <repository_url>

This sets the new remote.

Execute the following command to verify the new remote URL:

$ git remote -v

Finally, push everything we have to remote, by executing the following command:

$ git push -u origin master

If you are asked for credentials, enter them and confirm by pressing Enter.

Key benefits

Build a full-fledged application in Spring and Kotlin

Architect your application to take a microservice-based approach in the cloud

Integrate your application with a variety of Spring components

Description

Kotlin is being used widely by developers because of its light weight, built-in null safety, and functional and reactive programming aspects. Kotlin shares the same pragmatic, innovative and opinionated mindset as Spring, so they work well together. Spring when combined with Kotlin helps you to reach a new level of productivity. This combination has helped developers to create Functional Applications using both the tools together. This book will teach you how to take advantage of these developments and build robust, scalable and reactive applications with ease. In this book, you will begin with an introduction to Spring and its setup with Kotlin. You will then dive into assessing the design considerations of your application. Then you will learn to use Spring (with Spring Boot) along with Kotlin to build a robust backend in a microservice architecture with a REST based collaboration, and leverage Project Reactor in your application. You’ll then learn how to integrate Spring Data and Spring Cloud to manage configurations for database interaction and cloud deployment. You’ll also learn to use Spring Security to beef up security of your application before testing it with the JUnit framework and then deploying it on a cloud platform like AWS.

What you will learn

Explore Spring 5 concepts with Kotlin

Learn both dependency injections and complex configurations

Utilize Spring Data, Spring Cloud, and Spring Security in your applications

Create efficient reactive systems with Project Reactor

Write unit tests for your Spring/Kotlin applications

Deploy applications on cloud platforms like AWS

What do you get with Print?

Instant access to your digital copy whilst your Print order is Shipped

Paperback book shipped to your preferred address

Redeem a companion digital copy on all Print orders

Access this title in our online reader with advanced features

DRM FREE - Read whenever, wherever and however you want

Frequently bought together

£36.99

Building Applications with Spring 5 and Kotlin

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Total £ 110.97

Nevyn Jul 12, 2018

If you are an absolute beginner who requires screenshots, then this book is for you. The only con for you then is that the writer is very brief in explaining things that for a beginner requires a deeper description.As for me (not a beginner). I paged through 15% of the book to get to the end of installing the tools you need. After that the next chapter described what Spring Framework is. MVC was explained on 3 pages, one for each component and even then only a small paragraph each. In all the chapter is like a bullet list of features which would be far too cryptic for a beginner. 20% of the book gets you nowhere.At that point I requested a refund.Why?The book seems like something rushed to be a first to cover the combined topics. The software covered are milestone and release candidates, except for Kotlin which is a major version behind. Why not wait for things to be released and then have an up to date and comprehensive book?I also get the feeling that the author was targeting the topic not out of in-depth knowledge of the components, but more due to it being a hot topic and having some exposure to the components.That's just my opinion.

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Building Applications with Spring 5 and Kotlin: Build scalable and reactive applications with Spring combined with the productivity of Kotlin

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