Spring Boot first web application
last modified July 29, 2023
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.
build.gradle
...
src
├───main
│ ├───java
│ │ └───com
│ │ └───zetcode
│ │ │ Application.java
│ │ └───controller
│ │ MyController.java
│ └───resources
│ │ application.properties
│ └───templates
│ index.peb
└───test
└───java
This is the project structure.
plugins {
id 'org.springframework.boot' version '3.1.1'
id 'io.spring.dependency-management' version '1.1.0'
id 'java'
}
group = 'com.zetcode'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'
repositories {
mavenCentral()
}
dependencies {
implementation 'io.pebbletemplates:pebble-spring-boot-starter:3.2.1'
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 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("${application.message}")
private String message = "Hi there";
@GetMapping("/")
public String index(Model model) {
model.addAttribute("now", LocalDate.now());
model.addAttribute("message", this.message);
return "index";
}
}
This is the controller class for the Spring Boot web application. A controller
is decorated with the @Controller annotation. The controller has
one mapping. The mapping resolves to the index.peb, which is
located in the resources/templates directory.
@Value("${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.peb
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.peb 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.
$ ./gradlew bootRun
We run the application. Now we can navigate to localhost:8080 to see
the application message.
In this article we have created our first Spring Boot web application.