SpringBootServletInitializer

last modified July 23, 2023

In this article we show how to deploy a Spring Boot application from a traditional WAR deployment.

The current trend is to deploy Spring Boot application from an executable JAR. (See the Spring Boot first web application for details how to start a simple web application from JAR.)

Spring is a popular Java application framework. Spring Boot is an effort to create stand-alone, production-grade Spring based applications with minimal effort.

SpringBootServletInitializer

SpringBootServletInitializer is an interface to run SpringApplication from a traditional WAR deployment. It binds Servlet, Filter and ServletContextInitializer beans from the application context to the server.

SpringBootServletInitializer example

The application creates a simple Spring Boot RESTful application and packages it into a WAR.

build.gradle … src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───controller │ │ MyController.java │ └───resources └───test └───java

This is the project structure.

build.gradle

plugins { id ‘org.springframework.boot’ version ‘3.1.1’ id ‘io.spring.dependency-management’ version ‘1.1.0’ id ‘java’ }

group = ‘com.example’ version = ‘0.0.1-SNAPSHOT’ sourceCompatibility = ‘17’

repositories { mavenCentral() }

dependencies { implementation ‘org.springframework.boot:spring-boot-starter-web’ }

This is the Gradle build file. The spring-boot-starter-web is starter for building web, including RESTful, applications using Spring MVC.

The application is packaged into a WAR file.

com/zetcode/controller/MyController.java

package com.zetcode.controller;

import org.springframework.http.MediaType; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController;

@RestController public class MyController {

@GetMapping(value = "/", produces = MediaType.TEXT_PLAIN_VALUE)
public String index() {

    return "Hello there";
}

}

This is the controller class for the Spring Boot web application. A controller is decorated with the @Restontroller annotation.

@GetMapping(value = “/”, produces = MediaType.TEXT_PLAIN_VALUE) public String index() {

return "Hello there";

}

A GET request to the home page returns a string. The binding is done with @GetMapping.

com/zetcode/Application.java

package com.zetcode;

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

@SpringBootApplication public class Application extends SpringBootServletInitializer {

public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
}

}

The Application sets up the Spring Boot application. It extends from SpringBootServletInitializer so that it can be deployed as a WAR.

The application can be run both by deploying the WAR on a Tomcat server and executing it as a self-executable web archive with embedded Tomcat.

In this article we have created our first Spring Boot web application deployable from a traditional WAR.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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