Spring Boot Hello World Example Thymeleaf

In this article, we will show you how to develop a Spring Boot web application, using Thymeleaf view, embedded Tomcat and package it as an executable JAR file.

Technologies used :

• Spring Boot 2.1.2.RELEASE
• Spring 5.1.4.RELEASE
• Thymeleaf 3.0.11.RELEASE
• Tomcat embed 9.0.14
• JUnit 4.12
• Maven 3
• Java 8

1. Project Directory

2. Maven

Put spring-boot-starter-web and spring-boot-starter-thymeleaf, it will get anything we need to develop a Spring MVC + Thymeleaf web application, including the embedded Tomcat server.

<?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>
    <artifactId>web-thymeleaf</artifactId>
    <packaging>jar</packaging>
    <name>Spring Boot Web Thymeleaf Example</name>
    <description>Spring Boot Web Thymeleaf Example</description>
    <version>1.0</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.2.RELEASE</version>
    </parent>
    <properties>
        <java.version>1.8</java.version>
        <bootstrap.version>4.2.1</bootstrap.version>
    </properties>
    <dependencies>
        <!-- web mvc -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- thymeleaf -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <!-- test -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- hot swapping, disable cache for template, enable live reload -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
        <!-- Optional, for bootstrap -->
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>bootstrap</artifactId>
            <version>${bootstrap.version}</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <!-- Package as an executable jar/war -->
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <addResources>true</addResources>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.0</version>
            </plugin>
        </plugins>
    </build>
</project>

Display the project dependencies.

$ mvn dependency:tree
[INFO] org.springframework.boot:web-thymeleaf:jar:1.0
[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:2.1.2.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter:jar:2.1.2.RELEASE:compile
[INFO] |  |  +- org.springframework.boot:spring-boot-starter-logging:jar:2.1.2.RELEASE:compile
[INFO] |  |  |  +- ch.qos.logback:logback-classic:jar:1.2.3:compile
[INFO] |  |  |  |  \- ch.qos.logback:logback-core:jar:1.2.3:compile
[INFO] |  |  |  +- org.apache.logging.log4j:log4j-to-slf4j:jar:2.11.1:compile
[INFO] |  |  |  |  \- org.apache.logging.log4j:log4j-api:jar:2.11.1:compile
[INFO] |  |  |  \- org.slf4j:jul-to-slf4j:jar:1.7.25:compile
[INFO] |  |  +- javax.annotation:javax.annotation-api:jar:1.3.2:compile
[INFO] |  |  \- org.yaml:snakeyaml:jar:1.23:runtime
[INFO] |  +- org.springframework.boot:spring-boot-starter-json:jar:2.1.2.RELEASE:compile
[INFO] |  |  +- com.fasterxml.jackson.core:jackson-databind:jar:2.9.8:compile
[INFO] |  |  |  +- com.fasterxml.jackson.core:jackson-annotations:jar:2.9.0:compile
[INFO] |  |  |  \- com.fasterxml.jackson.core:jackson-core:jar:2.9.8:compile
[INFO] |  |  +- com.fasterxml.jackson.datatype:jackson-datatype-jdk8:jar:2.9.8:compile
[INFO] |  |  +- com.fasterxml.jackson.datatype:jackson-datatype-jsr310:jar:2.9.8:compile
[INFO] |  |  \- com.fasterxml.jackson.module:jackson-module-parameter-names:jar:2.9.8:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-tomcat:jar:2.1.2.RELEASE:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-core:jar:9.0.14:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-el:jar:9.0.14:compile
[INFO] |  |  \- org.apache.tomcat.embed:tomcat-embed-websocket:jar:9.0.14:compile
[INFO] |  +- org.hibernate.validator:hibernate-validator:jar:6.0.14.Final:compile
[INFO] |  |  +- javax.validation:validation-api:jar:2.0.1.Final:compile
[INFO] |  |  +- org.jboss.logging:jboss-logging:jar:3.3.2.Final:compile
[INFO] |  |  \- com.fasterxml:classmate:jar:1.4.0:compile
[INFO] |  +- org.springframework:spring-web:jar:5.1.4.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-beans:jar:5.1.4.RELEASE:compile
[INFO] |  \- org.springframework:spring-webmvc:jar:5.1.4.RELEASE:compile
[INFO] |     +- org.springframework:spring-aop:jar:5.1.4.RELEASE:compile
[INFO] |     +- org.springframework:spring-context:jar:5.1.4.RELEASE:compile
[INFO] |     \- org.springframework:spring-expression:jar:5.1.4.RELEASE:compile
[INFO] +- org.springframework.boot:spring-boot-starter-thymeleaf:jar:2.1.2.RELEASE:compile
[INFO] |  +- org.thymeleaf:thymeleaf-spring5:jar:3.0.11.RELEASE:compile
[INFO] |  |  +- org.thymeleaf:thymeleaf:jar:3.0.11.RELEASE:compile
[INFO] |  |  |  +- org.attoparser:attoparser:jar:2.0.5.RELEASE:compile
[INFO] |  |  |  \- org.unbescape:unbescape:jar:1.1.6.RELEASE:compile
[INFO] |  |  \- org.slf4j:slf4j-api:jar:1.7.25:compile
[INFO] |  \- org.thymeleaf.extras:thymeleaf-extras-java8time:jar:3.0.2.RELEASE:compile
[INFO] +- org.springframework.boot:spring-boot-starter-test:jar:2.1.2.RELEASE:test
[INFO] |  +- org.springframework.boot:spring-boot-test:jar:2.1.2.RELEASE:test
[INFO] |  +- org.springframework.boot:spring-boot-test-autoconfigure:jar:2.1.2.RELEASE:test
[INFO] |  +- com.jayway.jsonpath:json-path:jar:2.4.0:test
[INFO] |  |  \- net.minidev:json-smart:jar:2.3:test
[INFO] |  |     \- net.minidev:accessors-smart:jar:1.2:test
[INFO] |  |        \- org.ow2.asm:asm:jar:5.0.4:test
[INFO] |  +- junit:junit:jar:4.12:test
[INFO] |  +- org.assertj:assertj-core:jar:3.11.1:test
[INFO] |  +- org.mockito:mockito-core:jar:2.23.4:test
[INFO] |  |  +- net.bytebuddy:byte-buddy:jar:1.9.7:test
[INFO] |  |  +- net.bytebuddy:byte-buddy-agent:jar:1.9.7:test
[INFO] |  |  \- org.objenesis:objenesis:jar:2.6:test
[INFO] |  +- org.hamcrest:hamcrest-core:jar:1.3:test
[INFO] |  +- org.hamcrest:hamcrest-library:jar:1.3:test
[INFO] |  +- org.skyscreamer:jsonassert:jar:1.5.0:test
[INFO] |  |  \- com.vaadin.external.google:android-json:jar:0.0.20131108.vaadin1:test
[INFO] |  +- org.springframework:spring-core:jar:5.1.4.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-jcl:jar:5.1.4.RELEASE:compile
[INFO] |  +- org.springframework:spring-test:jar:5.1.4.RELEASE:test
[INFO] |  \- org.xmlunit:xmlunit-core:jar:2.6.2:test
[INFO] |     \- javax.xml.bind:jaxb-api:jar:2.3.1:test
[INFO] |        \- javax.activation:javax.activation-api:jar:1.2.0:test
[INFO] +- org.springframework.boot:spring-boot-devtools:jar:2.1.2.RELEASE:compile (optional)
[INFO] |  +- org.springframework.boot:spring-boot:jar:2.1.2.RELEASE:compile
[INFO] |  \- org.springframework.boot:spring-boot-autoconfigure:jar:2.1.2.RELEASE:compile
[INFO] \- org.webjars:bootstrap:jar:4.2.1:compile
[INFO]    +- org.webjars:jquery:jar:3.0.0:compile
[INFO]    \- org.webjars:popper.js:jar:1.14.3:compile

3. Developer Tools

	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-devtools</artifactId>
		<optional>true</optional>
	</dependency>

This spring-boot-devtools helps to disable the caches and enable hot swapping so that developers will always see the last changes. Good for development. Read this – Spring Boot – Developer tools Try to modify the Thymeleaf templates or properties files, refresh the browser to see the changes take effect immediately.

• For Eclipse IDE, it is integrated well with spring-boot-devtools.
• For Intellij IDEA, extra steps are required, read this reload static file is not working

4. Spring Boot + MVC

4.1 A simple controller.

package com.mkyong.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 org.springframework.web.bind.annotation.RequestParam;
import java.util.Arrays;
import java.util.List;
@Controller
public class WelcomeController {
    // inject via application.properties
    @Value("${welcome.message}")
    private String message;
    private List<String> tasks = Arrays.asList("a", "b", "c", "d", "e", "f", "g");
    @GetMapping("/")
    public String main(Model model) {
        model.addAttribute("message", message);
        model.addAttribute("tasks", tasks);
        return "welcome"; //view
    // /hello?name=kotlin
    @GetMapping("/hello")
    public String mainWithParam(
            @RequestParam(name = "name", required = false, defaultValue = "") 
			String name, Model model) {
        model.addAttribute("message", name);
        return "welcome"; //view

4.2 Create a class and annotate with @SpringBootApplication. In IDE, run this class to start the entire web application.

package com.mkyong;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class StartWebApplication {
    public static void main(String[] args) {
        SpringApplication.run(StartWebApplication.class, args);

5. Thymeleaf + Static files

5.1 For Thymeleaf template files, put in src/main/resources/templates/

<!DOCTYPE HTML>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <title>Spring Boot Thymeleaf Hello World Example</title>
    <link rel="stylesheet" th:href="@{webjars/bootstrap/4.2.1/css/bootstrap.min.css}"/>
    <link rel="stylesheet" th:href="@{/css/main.css}"/>
</head>
<body>
<nav class="navbar navbar-expand-md navbar-dark bg-dark fixed-top">
    <a class="navbar-brand" href="#">Mkyong.com</a>
</nav>
<main role="main" class="container">
    <div class="starter-template">
        <h1>Spring Boot Web Thymeleaf Example</h1>
        <h2>
            <span th:text="'Hello, ' + ${message}"></span>
        </h2>
    </div>
    <ol>
        <li th:each="task : ${tasks}" th:text="${task}"></li>
    </ol>
</main>
<!-- /.container -->
<script type="text/javascript" th:src="@{webjars/bootstrap/4.2.1/js/bootstrap.min.js}"></script>
</body>
</html>

5.2 Spring Boot common application properties

welcome.message: Mkyong
spring.thymeleaf.cache=false

5.3 For Static files like CSS or JS, put in src/main/resources/static/

body {
  padding-top: 5rem;
.starter-template {
  padding: 3rem 1.5rem;
  text-align: center;
h1{
	color:#0000FF;
h2{
	color:#FF0000;

6. Unit Test

MockMvc to test the Spring MVC controller.

package com.mkyong;
import com.mkyong.controller.WelcomeController;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.MvcResult;
import org.springframework.test.web.servlet.ResultActions;
import org.springframework.web.servlet.ModelAndView;
import java.util.Arrays;
import java.util.List;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.core.IsEqual.equalTo;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@RunWith(SpringRunner.class)
@WebMvcTest(controllers = WelcomeController.class)
public class WelcomeControllerTest {
    @Autowired
    private MockMvc mockMvc;
    List<String> expectedList = Arrays.asList("a", "b", "c", "d", "e", "f", "g");
    @Test
    public void main() throws Exception {
        ResultActions resultActions = mockMvc.perform(get("/"))
                .andExpect(status().isOk())
                .andExpect(view().name("welcome"))
                .andExpect(model().attribute("message", equalTo("Mkyong")))
                .andExpect(model().attribute("tasks", is(expectedList)))
                .andExpect(content().string(containsString("Hello, Mkyong")));
        MvcResult mvcResult = resultActions.andReturn();
        ModelAndView mv = mvcResult.getModelAndView();
        //
    // Get request with Param
    @Test
    public void hello() throws Exception {
        mockMvc.perform(get("/hello").param("name", "I Love Kotlin!"))
                .andExpect(status().isOk())
                .andExpect(view().name("welcome"))
                .andExpect(model().attribute("message", equalTo("I Love Kotlin!")))
                .andExpect(content().string(containsString("Hello, I Love Kotlin!")));

7. Demo

$ mvn spring-boot:run
: Tomcat initialized with port(s): 8080 (http)
: Starting service [Tomcat]
: Starting Servlet engine: [Apache Tomcat/9.0.14]
: Tomcat started on port(s): 8080 (http) with context path ''
 Started StartWebApplication in 1.858 seconds (JVM running for 2.222)

URL = http://localhost:8080

URL = http://localhost:8080/hello?name=abc

8. Create an executable JAR

For deployment, just normal Maven package to create an executable JAR file.

$ mvn clean package
$ java -jar target\web-thymeleaf-1.0.jar