Spring Boot first web application
last modified July 6, 2020
Spring Boot first web application tutorial shows how to create a simple Spring Boot web application. The current trend is to launch Spring Boot applications from an executable JAR. (See SpringBootServletInitializer tutorial for an example of a traditional WAR deployment.)
Spring is a popular Java application framework. Spring Boot is an effort to create stand-alone, production-grade Spring based applications with minimal effort.
Spring Boot web application example
The application shows a message and today's date. The message is retrieved from an appplication's property.
pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───controller │ │ MyController.java │ └───resources │ │ application.properties │ └───templates │ index.pebble └───test └───java
This is the project structure.
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>springbootfirstweb</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.2.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>io.pebbletemplates</groupId> <artifactId>pebble-spring-boot-starter</artifactId> <version>3.1.2</version> </dependency> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
This is the Maven build file. The spring-boot-starter-web
is starter for
building web, including RESTful, applications using Spring MVC.
The pebble-spring-boot-starter
contains the Pebble template engine.
When Spring Boot detects this starter, it automatically configures Pebble for us.
The application is packaged into a JAR file, which contains an embedded Tomcat web server.
application.message: Hello there
The application.properties
file contains various configuration
settings of a Spring Boot application. We have one custom message option.
package com.zetcode.controller; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.GetMapping; import java.time.LocalDate; import java.util.Map; @Controller public class MyController { @Value("${application.message}") private String message = "Hi there"; @GetMapping("/") public String index(Model model) { model.addAttribute("now", LocalDate.now()); model.addAttribute("message", this.message); return "index"; } }
This is the controller class for the Spring Boot web application. A controller is decorated with
the @Controller
annotation. The controller has one mapping. The mapping resolves
to the index.pebble
, which is located in the resources/templates
directory.
@Value("${application.message}") private String message = "Hi there";
We inject a value from the application.properties
into the message
variable.
@GetMapping("/") public String index(Model model) { model.addAttribute("now", LocalDate.now()); model.addAttribute("message", this.message); return "index"; }
The @GetMapping
annotation maps a GET request with the /
path to the index method handler. A model is created and filled with data.
Spring Boot resolves the index
view to the index.pebble
template file, to which it also sends the model data.
<!DOCTYPE html> <html lang="en"> <head> <title>Home page</title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> </head> <body> <p> Today: {{ now }} </p> <p> Message: {{ message }} </p> </body> </html>
The index.pebble
displays two values: the current date and the received message.
Both values are passed to the template via the controller.
<p> Today: {{ now }} </p>
Pebble uses the {{}}
syntax to display the variable.
package com.zetcode; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
The Application
sets up the Spring Boot application.
$ mvn spring-boot:run
We run the application. Now we can navigate to localhost:8080
to see
the application message.
In this tutorial, we have created our first Spring Boot web application.