Spring with Spark Framework for Microservices

Recently, my team decided to use Spark to build our new REST api.  Spark seems easy with less coding.  We still wanted to use Spring for dependency injection.  We also wanted to use Tomcat as the standalone web container.  After some research, we figured out how to build the REST api with Spring, Spark and Tomcat.

1. Create class SpringSparkFilter which extends SparkFilter. Override method getApplication:

   	@Override
   	protected SparkApplication getApplication(FilterConfig filterConfig) throws ServletException {
   	Class<?>[] configClasses = getConfigClasses(filterConfig);
   	try (AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(configClasses)) {
   	String applicationClassName = filterConfig.getInitParameter(APPLICATION_CLASS_PARAM);
   	try {
   	return (SparkApplication) context.getBean(Class.forName(applicationClassName));
   	} catch (ClassNotFoundException e) {
   	throw new ServletException(e);
   	}
   	}
   	}

   view raw SpringSparkFilter.java hosted with ❤ by GitHub
2. Create class MySparkApplication, which implements SparkApplication. Implement init method:

   	@Override
   	public void init() {
   	get("/my-resource", (req, res) -> {
   	return exampleService.getDate();
   	});
   	}

   view raw MySparkApplication.java hosted with ❤ by GitHub
3. Configure web.xml to use SpringSparkFilter:

   	<filter>
   	<filter-name>SpringSparkFilter</filter-name>
   	<filter-class>com.zhentao.sparkjava.example.SpringSparkFilter</filter-class>
   	<init-param>
   	<param-name>applicationClass</param-name>
   	<param-value>com.zhentao.sparkjava.example.MySparkApplication</param-value>
   	</init-param>
   	<init-param>
   	<!-- Configuration locations must consist of one or more comma-delimited fully-qualified @Configuration classes -->
   	<param-name>springConfigLocation</param-name>
   	<param-value>com.zhentao.sparkjava.example.SpringConfig</param-value>
   	</init-param>
   	</filter>

   view raw web.xml hosted with ❤ by GitHub

Then either build a war file, and deploy it to tomcat or use tomcat7-maven-plugin for test run.  I usually use tomcat7-maven-plugin for fast development.  Here is the command:

mvn tomcat7:run

Then access http://localhost:8080/current-date.  The complete example can be found here.