Hello World with Spring MVC and Gradle.md

Hello World with Spring MVC and Gradle

I am a Ruby and JavaScript developer learning Java. Java-land is vast. There are a number of crufty frameworks and antiquated approaches. Don't get mired in those. Use Spring MVC and Gradle.

What follows is a 'Hello World' application using those Java technologies. Additionally, it does not require the Eclipse IDE which so many other Java tutorials defer to for some reason. I strongly prefer the command line to an IDE.

You can get the finished source of this tutorial here.

Install Gradle

brew install gradle

Setup and Configuration

With Spring, you have to setup the directory structure for your application and also wire together some boilerplate configuration. That is by design as far as I can tell.

Let's set things up.

mkdir hello-spring
cd hello-spring 
mkdir -p src/main/java/com/scottmotte/controller
mkdir -p src/main/java/com/scottmotte/springconfig
mkdir -p src/main/webapp/WEB-INF/spring
mkdir -p src/main/webapp/WEB-INF/view

Next, we need a build.gradle file. Gradle is sort of a cross between grunt.js and bundler.

vim build.gradle

Paste the following.

apply plugin: 'war'
apply plugin: 'jetty'

repositories {
   mavenCentral()
}

dependencies {
   providedCompile 'javax.servlet:servlet-api:2.5'
   compile 'org.springframework:spring-webmvc:3.2.2.RELEASE'
   runtime 'javax.servlet:jstl:1.1.2'
}

/* Change context path (base url). otherwise defaults to name of project */
jettyRunWar.contextPath = ''

Now, we need a web.xml configuration file. I don't yet understand why this is necessary.

vim src/main/webapp/WEB-INF/web.xml

Paste the following.

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <servlet>
    <servlet-name>sample</servlet-name>
    <servlet-class>
        org.springframework.web.servlet.DispatcherServlet
    </servlet-class>
    <init-param>
      <param-name>contextClass</param-name>
      <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
    </init-param>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>com.scottmotte.springconfig</param-value>
    </init-param>
  </servlet>

  <servlet-mapping>
    <servlet-name>sample</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

</web-app>

Finally, we need a WebConfig.java.

vim src/main/java/com/scottmotte/springconfig/WebConfig.java

Paste the following.

package com.scottmotte.springconfig;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration
@EnableWebMvc
@ComponentScan(basePackages="com.scottmotte.controller")
public class WebConfig {

  @Bean
  public InternalResourceViewResolver viewResolver() {
    InternalResourceViewResolver resolver = new InternalResourceViewResolver();
    resolver.setPrefix("/WEB-INF/view/");
    resolver.setSuffix(".jsp");
    return resolver;
  }

}

Application Code

We finished wiring up the configuration. We can now write our application code.

We begin by writing a controller. This will catch our url route, pass a string variable to the view, and load the view.

vim src/main/java/com/scottmotte/controller/SampleController.java

Paste the following.

package com.scottmotte.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class SampleController {

  @RequestMapping("/")
  public String loadHomePage(Model m) {
    m.addAttribute("message", "Hello World!");
    return "index";
  }
}

Next, write the view.

vim src/main/webapp/WEB-INF/view/index.jsp

Paste the following.

<!DOCTYPE HTML>
<html>
  <head>
    <title>Sample Application</title>
  </head>
  <body>
  <h1>${message}</h1>
  </body>
</html>

That's it. The actual code to write Hello World was not too bad - a controller and a view.

Run the server

Now, we can run the app.

gradle jettyRunWar

And visit http://localhost:8080. You should see 'Hello World'. Congratulations, you just wrote your first modern Java application.

My personal opinion is that there is still much more ceremony here than is necessary. The folder structure alone is unbelievably nested and ill-named. However, I will press on with Java.