Containerless Spring MVC

Many of the new JVM-based web frameworks are ditching containers and WAR files and instead using a WAR-less / Containerless approach. But that doesn’t mean you have to ditch your favorite Java web framework. A while back I posted about going containerless with Tapestry. Now lets do the same with Spring MVC. You can grab the full source code from GitHub.

First we need a build that defines the dependencies. Here is the build.gradle file for my Gradle build:

apply plugin:'java'
apply plugin:'application'
 
version = '0.0.1-SNAPSHOT'
 
mainClassName = "com.jamesward.Webapp"
applicationName = "webapp"
 
repositories {
    mavenCentral()
}
 
dependencies {
    compile 'org.springframework:spring-webmvc:3.1.2.RELEASE'
    compile 'cglib:cglib:2.2.2'
    compile 'org.eclipse.jetty:jetty-webapp:8.1.5.v20120716'
}

There isn’t much to this build except a few dependencies: Spring MVC, CGLib, and Jetty.

The src/main/resources/assets/index.html file just contains simple HTML:

<!doctype html>
<html>
<body>
hello, world
</body>
</html>

The src/main/java/com/jamesward/WebConfig.java file uses Spring annotations to configure Spring MVC:

package com.jamesward;
 
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.*;
 
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
 
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/**").addResourceLocations("classpath:/assets/");
    }
 
    @Override
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("/").setViewName("redirect:index.html");
    }
 
}

Finally, a simple “static void main” Java class is used to start Jetty. The src/main/java/com/jamesward/Webapp.java file just sets up the HTTP listener and starts it:

package com.jamesward;
 
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;
 
 
public class Webapp {
 
    public static void main(String[] args) throws Exception {
 
        final AnnotationConfigWebApplicationContext applicationContext = new AnnotationConfigWebApplicationContext();
        applicationContext.register(WebConfig.class);
 
        final ServletHolder servletHolder = new ServletHolder(new DispatcherServlet(applicationContext));
        final ServletContextHandler context = new ServletContextHandler();
        context.setContextPath("/");
        context.addServlet(servletHolder, "/*");
 
        String webPort = System.getenv("PORT");
        if (webPort == null || webPort.isEmpty()) {
            webPort = "8080";
        }
 
        final Server server = new Server(Integer.valueOf(webPort));
 
        server.setHandler(context);
 
        server.start();
        server.join();
    }
 
}

That’s it! To build and run this project locally you can simple run:

./gradlew run

(Note: Run “gradlew.bat” on Windows.)

So simple it’s hard to believe it works. :) Let me know if you have any questions.