Convert Spring Boot to Deployable WAR for Tomcat

This post demonstrates how to convert your Spring Boot web application to a deployable WAR file for Tomcat.

Create a Spring Boot Web Application

Step 1: Create a new project using Spring Initialzr

Click Next.

Step 2: Provide Project Details

Notice the Packaging is set Jar.

Choose Web and Thymeleaf. Click Next.

Step 3: Complete New Project

Click Finish.

Once the project creation is complete, you’ll have a project with this structure:

Create a Simple Controller

Create a simple controller the displays a text on a web page.

package com.turreta.springboot2tomcat.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class HiController {

    @RequestMapping("/hi")
    @ResponseBody
    public String hello(){
        return "Hi from Turreta.com";
    }
}

package com.turreta.springboot2tomcat.controller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.ResponseBody;

@Controller

public class HiController {

@RequestMapping("/hi")

@ResponseBody

public String hello(){

return "Hi from Turreta.com";

}

Sample Output

Our simple controller displays the following.

Convert to Deployable WAR for Tomcat

Step 1: Modify SpringBootToTomcatApplication

Modify SpringBootToTomcatApplication to:

Extend SpringBootServletInitializer
Override the configure method

package com.turreta.springboot2tomcat;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.support.SpringBootServletInitializer;

@SpringBootApplication
public class SpringBootToTomcatApplication extends SpringBootServletInitializer {

	/**
	 * Used when running as a jar
	 *
	 * @param args
	 */
	public static void main(String[] args) {
		SpringApplication.run(SpringBootToTomcatApplication.class, args);
	}

	/**
	 * Used when running as a WAR within a web container
	 * @param builder
	 * @return
	 */
	@Override
	protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
		return builder.sources(SpringBootToTomcatApplication.class);
	}
}

package com.turreta.springboot2tomcat;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.boot.builder.SpringApplicationBuilder;

import org.springframework.boot.web.support.SpringBootServletInitializer;

@SpringBootApplication

public class SpringBootToTomcatApplication extends SpringBootServletInitializer {

/**

* Used when running as a jar

* @param args

public static void main(String[] args) {

SpringApplication.run(SpringBootToTomcatApplication.class, args);

}

/**

* Used when running as a WAR within a web container

* @param builder

* @return

@Override

protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {

return builder.sources(SpringBootToTomcatApplication.class);

}

Step 2: Change POM packaging from JAR to WAR

Open your pom.xml up and change packaging from jar to war.

Packaging the WAR

When you run the mvn package this time, WAR files are now created.

war.original

There are two (2) files generated – .war and .war.original

The .war.original file doesn’t contain Spring Framework classes to boot your application up; while, .war includes all the needed Spring Framework classes.

So, which one to use in Tomcat?

Use the .war file.