Spring Boot Web using Undertow Embedded Servlet Container

Introduction

In this Spring Boot tutorial, we learn how to use Undertow as an embedded servlet container in Spring Boot Web application.

Create New Spring Boot Web Project

Open Spring Tool Suite IDE, select menu File > New > Spring Starter Project.

On the New Spring Starter Project popup input new project information as below and click Next.

Name: spring-boot-undertow
Group: dev.simplesolution
Artifact: spring-boot-api-doc
Version: 1.0.0
Description: Spring Boot using Undertow
Package: dev.simplesolution.undertow

Spring Boot Web using Undertow Embedded Servlet Container

On the New Spring Starter Project Dependencies popup choose dependencies as below and click Next.

Thymeleaf
Spring Web

Spring Boot Web using Undertow Embedded Servlet Container

Keep the information on the next popup as default and click Finish.

Spring Boot Web using Undertow Embedded Servlet Container

What is Undertow?

Undertow is a flexible performant web server written in java, providing both blocking and non-blocking API’s based on NIO.

To have more information about the Undertow servlet container library you can visit the Undertow homepage at undertow.io

Add Spring Boot Starter Undertow to your Spring Boot project

Spring Boot provides a starter for using Undertow as the embedded servlet container named Spring Boot Starter Undertow. We can use Spring Boot Starter Undertow as an alternative to Spring Boot’s default Tomcat servlet container.

To use the Spring Boot Starter Undertow Java library in the Gradle build project, add the following dependency into the build.gradle file. And exclude spring-boot-starter-tomcat module from spring-boot-starter-web.

implementation 'org.springframework.boot:spring-boot-starter-undertow:2.4.3'
implementation ('org.springframework.boot:spring-boot-starter-web') {
	exclude module: 'spring-boot-starter-tomcat'
}

To use the Spring Boot Starter Undertow Java library in the Maven build project, add the following dependency into the pom.xml file. And exclude spring-boot-starter-tomcat module from spring-boot-starter-web.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-undertow</artifactId>
  <version>2.4.3</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>

Implement Sample Controller and View

In the package dev.simplesolution.undertow, create a new class named IndexController.

package dev.simplesolution.undertow;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class IndexController {
	
	@GetMapping("/")
	public String index() {
		return "index";
	}

}

Create new HTML view file at \src\main\resources\templates\index.html

<!DOCTYPE html>
<html>
	<body>
		<h1>Web App using Undertow Servlet Container</h1>
	</body>
</html>

Run the application, we can see

  .   ____          _            __ _ _ __ _ \ \ \ \ \/ _` | \ \ \ \ ) ) ) ) | / / / / (v2.4.3) main] d.s.u.SpringBootUndertowApplication      : Starting SpringBootUndertowApplication using Java 1.8.0_231 on ss with PID 19148 (D:\SimpleSolution\spring-boot-undertow\bin\main started by SS in D:\SimpleSolution\spring-boot-undertow) main] d.s.u.SpringBootUndertowApplication      : No active profile set, falling back to default profiles: default main] io.undertow.websockets.jsr               : UT026010: Buffer pool was not set on WebSocketDeploymentInfo, the default pool will be used main] io.undertow.servlet                      : Initializing Spring embedded WebApplicationContext main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 436 ms main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor' main] o.s.b.a.w.s.WelcomePageHandlerMapping    : Adding welcome page template: index main] io.undertow                              : starting server: Undertow - 2.2.4.Final main] org.xnio                                 : XNIO version 3.8.0.Final main] org.xnio.nio                             : XNIO NIO Implementation Version 3.8.0.Final main] org.jboss.threads                        : JBoss Threads version 3.1.0.Final main] o.s.b.w.e.undertow.UndertowWebServer     : Undertow started on port(s) 8080 (http) main] d.s.u.SpringBootUndertowApplication      : Started SpringBootUndertowApplication in 0.973 seconds (JVM running for 1.865)

Open the link http://localhost:8080/ on your browser to see the web page as below.

Spring Boot Web using Undertow Embedded Servlet Container

Final Application Source Code

At this step we have the complete Spring Boot web project with code structure as below.

Spring Boot Web using Undertow Embedded Servlet Container

Download Source Code

The source code in this article can be found at: github.com/simplesolutiondev/spring-boot-undertow

or clone at:

git clone https://github.com/simplesolutiondev/spring-boot-undertow.git

or download at:

Download Source Code

Happy Coding 😊