Embedding tomcat server into an application

What is an embedded server?

A web application runs on a web server, usually they are packaged in a WAR file and deployed in a server container like Tomcat, JBOSS or GlassFish. However embedded servers provide an interesting alternative. Instead of deploying your app in a server, the server is embedded inside your application The result is a standalone application packaged in a jar file and that could be executed from a command line.

To run an embedded tomcat server we just need following jars

tomcat-embed-core
tomcat-embed-logging-juli

Find this project on Github

https://github.com/javacodenet/embeddedTomcatDemo

pom.xml

	<?xml version="1.0" encoding="UTF-8"?>
	<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javacodenet</groupId>
	<artifactId>embedded-tomcat-demo</artifactId>
	<version>1.0-SNAPSHOT</version>
	<dependencies>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-core</artifactId>
	<version>8.0.1</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-logging-juli</artifactId>
	<version>8.0.1</version>
	</dependency>
	</dependencies>
	</project>

view raw pom.xml hosted with ❤ by GitHub

EmbeddedTomcatStarter.java

	import org.apache.catalina.Context;
	import org.apache.catalina.LifecycleException;
	import org.apache.catalina.startup.Tomcat;
	import javax.servlet.ServletException;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;
	import java.io.*;
	import java.util.Properties;
	public class EmbeddedTomcatStarter {
	public static void main(String[] args)
	throws LifecycleException, InterruptedException, ServletException {
	Tomcat tomcat = new Tomcat();
	int port = Integer.parseInt(getPort());
	tomcat.setPort(port);
	Context context = tomcat.addContext("/", new File(".").getAbsolutePath());
	addServletToTomcat(port, context);
	context.addServletMapping("/*", "embeddedTomcat");
	tomcat.start();
	tomcat.getServer().await();
	}
	private static String getPort() {
	String port = null;
	InputStream input = null;
	try {
	Properties properties = new Properties();
	input = new FileInputStream("src/main/resources/application.properties");
	properties.load(input);
	//read server.port from application properties
	port = properties.getProperty("server.port");
	} catch (IOException ex) {
	ex.printStackTrace();
	} finally {
	if (input != null) {
	try {
	input.close();
	} catch (IOException e) {
	e.printStackTrace();
	}
	}
	}
	//if port is not configured then it will defaulted to 8080
	return port != null ? port : "8080";
	}
	private static void addServletToTomcat(final int port, Context context) {
	Tomcat.addServlet(context, "embeddedTomcat", new HttpServlet() {
	protected void service(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
	Writer writer = response.getWriter();
	writer.write("Embedded Tomcat Server is Running at:" + port);
	writer.flush();
	}
	});
	}
	}

view raw EmbeddedTomcatStarter.java hosted with ❤ by GitHub

application.properties

server.port = 8585

view raw application.properties hosted with ❤ by GitHub

Output