Spring Boot Deploy WAR file to Tomcat

In this article, we will show you how to create a Spring Boot traditional WAR file and deploy to a Tomcat servlet container.

In Spring Boot, to create a WAR for deployment, we need 3 steps:

1. Extends SpringBootServletInitializer
2. Marked the embedded servlet container as provided.
3. Update packaging to war

Tested with

• Spring Boot 2.1.2.RELEASE
• Tomcat 8 and 9
• Maven 3

1. Extends SpringBootServletInitializer

Update the @SpringBootApplication class to extend SpringBootServletInitializer, and override the configure method.

1.1 Classic Spring Boot JAR deployment.

import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class StartWebApplication {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(StartWebApplication.class, args);

1.2 For WAR deployment.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
@SpringBootApplication
public class StartWebApplication extends SpringBootServletInitializer {
    public static void main(String[] args) {
        SpringApplication.run(StartWebApplication.class, args);
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(StartWebApplication.class);
/*@SpringBootApplication
public class StartWebApplication {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(StartWebApplication.class, args);
}*/

For multiple main classes, make sure tell Spring Boot which main class to start :

  <properties>
      <!-- The main class to start by executing java -jar -->
      <start-class>com.mkyong.SpringBootWebApplication</start-class>
  </properties>

Read this – Spring Boot – Which main class to start

2. Marked the embedded servlet container as provided

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-thymeleaf</artifactId>
	</dependency>
	<!-- marked the embedded servlet container as provided -->
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-tomcat</artifactId>
		<scope>provided</scope>
	</dependency>
</dependencies>

3. Update packaging to war

  <packaging>war</packaging>

Done, build the project and copy the WAR file for deployment.