Spring-Boot / Groovy / MVC “Hello World” example

The complete project can be found here:
https://github.com/mtrojahn/spring-boot-groovy-mvc-simple

This is yet another very basic example. This time I’ll show how to create get a Web-MVC Spring-Boot project started. You will notice I take the no-XML approach and I’ll try to keep my examples as XML-free as they can be because it’s hard to find fresh documentation about it on the Web.

So, let me start with the build.gradle file:

group 'com.mtrojahn'
version '1.0-SNAPSHOT'

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.springframework.boot:spring-boot-gradle-plugin:1.3.0.RELEASE"
    }
}

apply plugin: 'groovy'
apply plugin: 'spring-boot'

repositories {
    mavenCentral()
}

sourceCompatibility = 1.8
targetCompatibility = 1.8

dependencies {
    compile "org.springframework.boot:spring-boot-starter-web"
    compile 'org.codehaus.groovy:groovy-all'
    testCompile "junit:junit"
}

bootRun {
    addResources = true
}

As you can see, no big changes from my previous example. Basically all you have to do is change spring-boot-starter to spring-boot-starter-web.

Ok, now let’s have a look on the our main class:

package com.mtrojahn

package com.mtrojahn

import org.springframework.boot.Banner
import org.springframework.boot.autoconfigure.EnableAutoConfiguration
import org.springframework.boot.builder.SpringApplicationBuilder
import org.springframework.context.annotation.ComponentScan

@EnableAutoConfiguration
@ComponentScan(basePackages = "com.mtrojahn.mvc")
class Application {
    static main(args) {
        new SpringApplicationBuilder()
                .sources(Application.class)
                .bannerMode(Banner.Mode.OFF)
                .run()
    }
}

I didn’t use @SpringBootApplication this time because I wanted to add a little configuration to it:

The @EnableAutoConfiguration annotation tells Spring-Boot to configure beans based on what it sees on my classpath. It will see spring-webmvc and flag this as a web application. Spring-Boot will provide you an embedded Tomcat server that will listen on port 8080 as default, among other things.

@ComponentScan configures the scanning for @Configuration classes and in this case it’s telling Spring to scan the package that holds my MVC Controller.

Here’s the MVC Controller:

package com.mtrojahn.mvc

import org.springframework.stereotype.Controller
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.ResponseBody

@Controller
class MvcController {
    @RequestMapping(value = "/")
    def @ResponseBody hello() {
        return "Hello World!"
    }
}

This @Controller will just show the traditional “Hello World!” message when you point your browser to “http://localhost:8080/”. The @RequestMapping annotation is responsible for mapping the URL “/” to the method “hello()” which just returns a string.

That’s it, folks.