Intro to Spring Boot: Controllers

Notes

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

• Web development is simplified even more in Spring Boot than in Spring
• It provides Tomcat as an embedded web server
• A lot of settings are preconfigured for us so there's no need for additional XML configuration

Create a Simple Spring Boot Project

• Go to start.spring.io
• Select Gradle Project, Java, and 1.5.x (that is, the most recent 1.5 non-SNAPSHOT release) from the dropdown for "Generate a ___ with ___ and Spring Boot ___"
• Put the title for your project, hello-spring, in the section marked Artifact
• Search for and add the following dependencies: Web, Thymeleaf, DevTools then click "Generate"
• Move the downloaded unzipped folder from downloads into another location such as LC101 or your home directory
• Start IntelliJ
• Select Import Project and browse to where you put the downloaded file
• Select "Create project from existing sources"
• Accept all defaults as you create the project
• If you see an Unlinked Gradle Project popup, go ahead and click "Import Gradle Project", then check the "Use auto-import" box and leave everything else as it is.

• To run the application, click on the Gradle icon on the side, then go into Tasks->application and double-click bootRun

• You can then visit the corresponding web page at localhost:8080 (Right now, you'll see an error page, but we'll fix that below.) Now go ahead and stop the application.

Create a Controller for your Spring Boot Project

• First, add the necessary classes to your src->main->java->org.yourorgname->HelloSpringApplication: SpringBootApplication and SpringApplication.
• Next, go to src->main->java and right click on your org.yourorgname package and then select New->Package and name your new package controllers.
• Add a New->Java Class to the package controllers and name it HelloController.
• Above the class definition for HelloController add the annotation @Controller and add the corresponding class to your project.
• Add this code to the body of your HelloController class:

  @RequestMapping(value="")
  @ResponseBody
  public String index(){
      return "Hello World";
  }

• Use Gradle to bootRun again and visit localhost:8080. You should see "Hello World"
• Now add another controller at another path by adding this code below the code posted above:

  @RequestMapping(value="goodbye")
  @ResponseBody
  public String goodbye(){
      return "Goodbye";
  }

• Run the application again and visit localhost:8080/goodbye and you should see "Goodbye".

Congratulations! You just ran your first Spring Boot program in IntelliJ!