Embedding Tomcat inside Java Program

Apache Tomcat is one of the most popular open source application servers that is been use today. What we usually do is run Tomcat server and deploy our webapps inside the Tomcat.
But we also can embed Tomcat inside our java application and do all stuffs through our own program. This is just a simple example showing how to embed the tomcat, start the server and put a servlet inside that.

I'm using Intellij Idea IDE. But you can use any IDE that you like. First create a new maven project and give an artifact id, group id and version that you like.

	<groupId>org.wso2.training.tomcat.embed</groupId>
	<artifactId>tomcat-embeded-sample</artifactId>
	<version>1.0-SNAPSHOT</version>

view raw gistfile1.txt hosted with ❤ by GitHub

We need to add following tomcat dependencies to the pom file.

	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-core</artifactId>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-logging-juli</artifactId>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-jasper</artifactId>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jasper</artifactId>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jasper-el</artifactId>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jsp-api</artifactId>
	</dependency>

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Finally pom file looks like

	<?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>org.wso2.training.tomcat.embed</groupId>
	<artifactId>tomcat-embeded-sample</artifactId>
	<version>1.0-SNAPSHOT</version>
	<url>http://maven.apache.org</url>
	<properties>
	<tomcat.version>7.0.34</tomcat.version>
	</properties>
	<dependencies>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-core</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-logging-juli</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat.embed</groupId>
	<artifactId>tomcat-embed-jasper</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jasper</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jasper-el</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	<dependency>
	<groupId>org.apache.tomcat</groupId>
	<artifactId>tomcat-jsp-api</artifactId>
	<version>${tomcat.version}</version>
	</dependency>
	</dependencies>
	</project>

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Now create a Java file with following content

	package org.wso2.training.tomcat.embed;
	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.File;
	import java.io.IOException;
	import java.io.PrintWriter;
	public class EmbeddedTomcat {
	public static void main(String[] args) throws LifecycleException {
	Tomcat tomcat = new Tomcat();
	tomcat.setPort(8888);
	Context ctx = tomcat.addContext("/", new File(".").getAbsolutePath());
	tomcat.addServlet(ctx, "HelloTomcat", new HttpServlet() {
	protected void service(HttpServletRequest req, HttpServletResponse resp)
	throws ServletException, IOException {
	PrintWriter responseWriter = resp.getWriter();
	responseWriter.println("You are running Tomcat in Embedded mode");
	responseWriter.flush();
	}
	});
	ctx.addServletMapping("/*", "HelloTomcat");
	tomcat.start();
	tomcat.getServer().await();
	}
	}

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Now run this class. When your program starts to run you will see some log entries getting on your console. If the sever get started successfully go to your web browser and type http://localhost:8888/
You will see something like following image on browser.