Initialize Spring

Spring Boot is a framework used to build Java web applications that implement the MVC pattern. For more about Spring, check out Spring IO .

As you code along with the videos, you will be working on your own project. Should you want to review a step or double-check your code, fork LaunchCode’s hello-spring-demo repository to see what the code looked like at each stage. The repository is up on Github . The starter branch contains the code after creation and also shows the starting point for the next chapter.

We suggest you create and checkout a new branch in your hello-spring repository for each video lesson. This will help you return to earlier states of your application to review your work, and is a convenient opportunity to practice your git workflow.

Initialize a Spring Boot Project - Video

Initialize a Spring Boot Project - Text

1. Go to start.spring.io .

2. For Project, select Gradle - Groovy Project.

3. For Language, select Java.

4. For Spring Boot, select the most recent non-SNAPSHOT release.

5. For Project Metadata/Group, enter org.launchcode.

   Note

   You can use whatever package name you want here. The convention is topleveldomain.domainname. In other words, the reverse of what you would see in a URL.

6. For Project Metadata/Artifact, enter hello-spring.

   Note

   This will also be the Name of your project. It will be added to the Package name as well.

7. For Project Metadata/Packaging, select Jar.

8. For Project Metadata/Java, select 17.

9. For Dependencies, search for and add the following: Spring Web, and Spring Boot DevTools.

   Note

   For some projects in this book, you’ll also need to add ThymeLeaf and Validation as dependencies.

10. Click Generate to create a .zip file of the project starter code.

Spring in IntelliJ

1. Move the downloaded, unzipped folder from your downloads folder into another location such as ClassWork or your home directory.
2. Start IntelliJ.
3. Select Open and browse to where you put the downloaded project. Unzip the project and select to import the top-level folder of the new Spring project.

The Spring Project Structure

The Spring Initializr gives us a number of helpful files and directories to get our Spring project up and running.

Within the src directory, you’ll find a familiar setup with both a main and test directory. Inside of main will be a java folder to house your packages and classes. Inside the java folder is a HelloSpringApplication. Opening this for the first time, you’ll likely see some import errors that can be resolved by clicking on the context menu to add the corresponding library to the classpath. Expanding the main method shows you the line that allows the application to run. We’ll run the app in the section below but won’t be working with much else with the main method in this course.

You’ll also find that there is a resources folder in main. resources is meant to hold your non-java code.

Outside of src, a .gitignore contains the basic items of our project that Spring expects to not be version controlled. These are files created by the IDE, the compiled code in the .build directory, and the gradle .jar and directory.

Gradle

Gradle is a Java tool that handles much of the work related to building and deploying software applications in Java. Your Spring project contains a file called build.gradle. As with most new tools, you do not need to know everything that this file does. For now, the takeaway is that Gradle manages the external dependencies in our project.

Do you remember specifying the dependencies of the Spring project? Scroll down to the bottom of your build.gradle file and you will see these items specified in a structure called dependencies.

   dependencies {
      implementation 'org.springframework.boot:spring-boot-starter-web'
      developmentOnly 'org.springframework.boot:spring-boot-devtools'
      testImplementation 'org.springframework.boot:spring-boot-starter-test'
   }

Gradle fetches these external packages from another location on the Internet so that we can use them in our project locally. That location is called the Maven central repository. The Maven central repository is a decentralized place for developers to post their code for others to use.

Before Running a Spring Project

Before running your project, we need to check the configuration of a few items.

1. In the gradle directory, open the subdirectory, wrapper, and then the file gradle-wrapper.properties inside of it. Ensure that the distributionUrl includes a gradle version of at least 7.0.

2. Open the test class, HelloSpringApplicationTests located in src/test/java/org.launchcode.hellospring. Run the single test. If you experience a JDK error, click on the Gradle Settings icon in the right-hand gradle pane and ensure that the Gradle JVM is using Java 17.

Running a Spring Project

To run the application, click on the Gradle icon on the side of your IntelliJ window. If you don’t see the Gradle side bar, click the panel icon in the bottom left corner of your window and select Gradle.

Once the Gradle panel is opened, go into Tasks. Here you’ll find the various tasks that Gradle can do for your project. Inside Tasks, open application and double-click bootRun. This will run our Spring Boot application.

Once the bootRun task is executed, you should see a new panel with running output about Tomcat.

Keep an eye out for a message that resembles:

   Started HelloSpringApplication in 1.739 seconds

While this message will change depending on the application you are running, this message indicates that the Spring Boot started up successfully. You’ll see an error message or a stack trace if there is an issue with your project preventing it from starting.

You’ll also notice a message in the output:

   Tomcat started on port(s): 8080 ...

Tomcat is the embedded web server within your Spring application. So this tells us that Tomcat is listening for requests on local port 8080. You can then visit the corresponding web page at localhost:8080. Right now, you’ll see an error page, but we’ll fix that soon. Now go ahead and stop the application by hitting the red square on the left side of the Run pane.

Check Your Understanding