Thursday, June 5, 2014

Spring Boot and AngularJS quick start

In this post I am going to show very simple and quick example of web application using Spring Boot with AngularJS. This app contains simple functionality of sending and storing imaginary messages. I've also used gradle for build management. All code is public and it is available on my github: https://github.com/rafalnowak/spring-boot-fun

Introduction to Spring Boot

Spring Boot is quite new project created under Spring Source umbrella. It was very few months ago when it reached version 1.0 and status of general availability. 

Most important and prominent goals of this projects are:
  • providing ability to create simple web apps very quickly
  • minimizing amount of XML codebloat which is usually necessary to configure every Spring application
  • most of app configuration is automatical
  • simplify running and deployment process by using embedded Tomcat or Jetty servers that can run our applications without special effort and deploy process
  • there are lot of so called spring boot starters which are packages containing default configuration for various fields of Spring like database access by JPA, aspect oriented programming or security
As we can see, it looks promising. In this post I'll show few basic steps necessary to create and boot simple Spring Boot web application.

First steps

Although Spring Boot can be used with special command line interface tools, I've decided to use it with very popular gradle build system.

Spring Boot comes with plugins to integrate with maven or gradle. They allow us to easily run application in embedded server. Necessary instructions to include these plugin are shown on snippet below:
buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.0.1.RELEASE")
    }
}
With this basic config we can proceed to next steps. In my sample project I've divided application into two modules: one contains persistence layer with domain object and JPA repositories and another contains presentation layer with controllers. Of course this completely optional and in such simple project it does not add any benefits. But it can show how to create multi module project in gradle. Next code fragment contains common configuration for all modules in our gradle build:
allprojects {
    apply plugin: "java"

    version = '1.0-SNAPSHOT'
    group = "info.rnowak.springBootFun"

    repositories {
        mavenLocal()
        mavenCentral()
    }

    dependencies {
        compile "org.springframework.boot:spring-boot-starter-test:1.0.1.RELEASE"
        compile "com.google.guava:guava:16.0.1"
        compile "com.h2database:h2:1.3.175"

        testCompile "junit:junit:4.11"
        testCompile "org.mockito:mockito-all:1.9.5"
        testCompile "org.assertj:assertj-core:1.5.0"
    }
}
Now when we have common configuration, we can declare basic modules of application:
project(":persistence") {
    dependencies {
        compile "org.springframework.boot:spring-boot-starter-data-jpa:1.0.1.RELEASE"

        testCompile project(":webapp")
    }
}

project(":webapp") {
    apply plugin: "spring-boot"

    dependencies {
        compile project(":persistence")
        compile "org.springframework.boot:spring-boot-starter-web:1.0.1.RELEASE"
    }
}
Most important parts are including special Spring Boot Starter packages and declaring usage of spring-boot plugin in one of subprojects.

Every starter packet contains dependencies for all necessary libraries used on given feature. For example, JPA starter has Hibernate dependencies and AOP starter contains spring-aop and AspectJ libraries. What is more, with this libraries Spring Boot provides also default configuration.

It is simple quick start configuration but it is enough for some starter applications.

Let's start fun with Spring!

Our next step should be creating of starting point of application. With Spring Boot it can be done by writing regular main method in some class. Now you only need to annotate this class with special Spring Boot auto configuration annotations and application is ready to run! Example of start class is shown below:
package info.rnowak.springFun;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;

@ComponentScan
@EnableAutoConfiguration
public class SpringFun {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(SpringFun.class);
        app.setShowBanner(false);
        app.run(args);
    }
}
Well, this step look simple but it has few interesting implications for all application.

Firstly, this class enables component scan for Spring managed beans with root package info.rnowak.springFun because it is placed in this package.

Another thing is that this main method allows to run application using command gradle run. By default it uses embedded Tomcat running on port 8080. Of course this behaviour can be changed and it is very well described in project documentation. It is also possible to create runnable jar from our application.

With main class defined we can create all other classes in our application like controllers, repositories, domain classes or services. But I won't show exact examples of such classes because they do not differ in any way from the same classes in old classic Spring. If you are interesed in my example, please take a look at the repository Spring Boot Fun repo.

Add some AngularJS

One of another "side effect" of Spring Boot main configuration class is that we get few default view resolvers. View resolver, in short version, is Spring feature, which maps names of view to specific view files.

Spring Boot with its default configuration sets lookup path for index.html file which will be served by default controller. Framework looks for this file in public/, webapp/ or resources/ directory on classpath. So you can just put index.html file in one of these locations and Spring Boot will create controller serving this view. And this is the way we can use AngularJS in our project. Of course it's not the only way but it is the simplest method for using AngularJS with Spring Boot application.

In our example application index.html file was placed in webapp/ directory and it looks like this:
<!DOCTYPE html>

<html ng-app="springFun">

<head>
    <link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">

    <script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
    <script src="//netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>

    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-beta.4/angular.min.js"></script>
    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-beta.4/angular-route.min.js"></script>
    <script src="js/application.js"></script>
    <script src="js/controllers.js"></script>
</head>

<body>

    <nav class="navbar navbar-default" role="navigation">
        <div class="container-fluid">
            <div class="navbar-header">
                <a class="navbar-brand" href="#/index">Spring Boot Fun</a>
            </div>
            <div class="collapse navbar-collapse">
                <ul class="nav navbar-nav">
                    <li><a href="#/list">Messages list</a></li>
                    <li><a href="#/about">About</a></li>
                </ul>
            </div>
        </div>
    </nav>

    <div ng-view></div>

    <footer class="text-center">
        Spring Boot Fun
    </footer>

</body>

</html>
This file includes all angular libraries used in project, controllers definition and main application module with routing defined.

The rest of files is available in repository mentioned earlier in post so I will not provide all listings here as it would be just waste of virtual space in post :)

Summary

As we can see, Spring Boot greatly decreases time needed to write and run simple Java web application. It reduces amount of XML configuration and provieds a lot of default values and conventions. But if we want to precisely set some settings, Spring Boot does not forbid it and programmer can manually set all the settings.

Also deploy of application is simplified because Spring Boot with gradle or maven plugin allows to run application in place with these tools. We can also create runnable jar that contains embedded Tomcat or Jetty. And if it is not desired by us, we can always use war plugin and create regular, traditional war and deploy it in classical way.

Spring Boot has also great documentation and I strongly encourage to read it by everybody interested in this tool: Spring Boot Docs