Hello Spring Boot

Creating a web app with the Spring Framework using Boot is quite easy, assuming you have already installed Spring Tool Suite, the Pivotal IDE based on Eclipse.

Actually, it is just a matter of selecting on the menu File, the item New, and there Spring Starter Project. There you are presented with a bunch of names to give and selection to make, I'd suggest you to check start.spring.io for inspiration, since this STS wizard it is nothing more than a proxy to that web page, that would guide you to the creation of a Spring application.

I named my project helloSpring, and then I kept all the main default settings, like the Maven support, jar generation, Java 1.8 language usage, and I only added one single item in Dependencies: Web.

What it is going to happen is that my Spring project would generate a single huge jar embedding Tomcat and all the required dependencies to let the application work. After confirming, Maven could take some time to get all the required jars. However in the end I'll have a nice project ready to be compiled. Even if it is not to do anything sensible at all.

I'd suggest you to have a look at the generated pom.xml file. You won't be surprise to find out that it shows the information you entered in the wizard.

Then, accessing the Project Explorer, you'll see in the Spring Elements a bean HelloSpringApplication (the prefix is the project name, if you chose a different name for it, you'll see the change reflected here).

Let's have a better look a this bean. I asked to the wizard to put the generated classes in the dd.manny.hello package, so there I'm going to find it.

There is not much to see, apart from that the class has been decorated with the @SpringBootApplication annotation, it contains a main() method that calls SpringApplication.run() passing the class itself. Even without knowing anything about Spring Boot, looks intuitive what is going on here. On startup Spring would see that this is the booting class, and would use its main to call the SpringApplication run() method.

Now I'd like to run this application, even I can't expect to get much feedback from it. The easiest way to do it, it is from the Spring Boot Dashboard. You should see that view in the bottom left of your STS window. If for any reason it is missing, you can get it back from Window - Show View - Spring - Boot Dashboard.

In the Boot Dashboard you should see a collapsed list named local. Open it and you should find your project. My one is there, named helloSpring. Now I can use the menu on the Boot Dashboard view, or right-click menu if I am in the mood for it, to start or restart it.

What I usually I get it now is a fat exception. This is because I have something else running on the 8080 port on my machine and STS is trying to run the embedded Tomcat for my application right on that port. If you get

java.net.BindException: Address already in use

You are having the same problem.

Not a big issue, tough. There is a file in the source/main/resources/ folder named application.properties that, not surprisingly, let us to set properties used by our application. Initially it is empty, I added this line:

server.port = 8585

Meaning that I want my Tomcat to use a different port from the standard one.

Now I can restart my application, and get a smooth startup, as showed by the error-free log in the Console view.

The full code for the project is on github.