Spring Boot WebApplicationType
last modified July 20, 2023
Spring Boot WebApplicationType tutorial presents various types of web applications in a Spring Boot application. The example shows how to set the WebApplicationType.
Spring Boot is a popular application framework for creating enterprise application in Java, Kotlin, or Groovy.
WebApplicationType
The WebApplicationType is an enumeration of possible types of web applications.
There are three possible values:
- NONE - the application should not run as a web application and should not start an embedded web server.
- REACTIVE - the application should run as a reactive web application and should start an embedded reactive web server.
- SERVLET - the application should run as a servlet-based web application and should start an embedded servlet web server.
Spring Boot example
In the following application, we define the web application type of a Spring Boot application.
build.gradle
...
src
├── main
│ ├── java
│ │ └── com
│ │ └── zetcode
│ │ └── Application.java
│ └── resources
└── test
└── java
This is the project structure of the Spring Boot application.
plugins {
id 'java'
id 'org.springframework.boot' version '3.1.1'
id 'io.spring.dependency-management' version '1.1.0'
}
group = 'com.zetcode'
version = '0.0.1-SNAPSHOT'
java {
sourceCompatibility = '17'
}
repositories {
mavenCentral()
}
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-webflux'
implementation 'org.springframework.boot:spring-boot-starter-web'
}
test {
useJUnitPlatform()
}
In the build.gradle file, we have dependencies for a classic
servlet and reactive web application.
package com.zetcode;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.ServerResponse;
import static org.springframework.web.reactive.function.BodyInserters.fromValue;
import static org.springframework.web.reactive.function.server.RequestPredicates.GET;
import static org.springframework.web.reactive.function.server.RouterFunctions.route;
import static org.springframework.web.reactive.function.server.ServerResponse.ok;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
new SpringApplicationBuilder(Application.class)
.web(WebApplicationType.SERVLET)
.run(args);
}
}
@RestController
class MyController {
@GetMapping("/")
public String hello() {
return "Home page";
}
}
@Configuration
class MyRoutes {
@Bean
RouterFunction<ServerResponse> about() {
return route(GET("/about"), request -> ok().body(fromValue("About page")));
}
}
@Component
class MyRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("Hello there!");
}
}
In the Application, we define the Spring Boot application and set up
a classic web rest point, a reactive route and a commandline runner.
new SpringApplicationBuilder(Application.class)
.web(WebApplicationType.SERVLET)
.run(args);
We define the web application type using the SpringApplicationBuilder.
For the WebApplicationType.SERVLET, the reactive route is not available.
$ ./gradlew bootRun
We start the application.
$ curl localhost:8080/ Home page
The classic servlet rest point is active.
In this article we have worked with a Spring Boot WebApplicationType.
