Spring Boot - Thymeleaf

Thymeleaf is a Java-based library used to create a web application. It provides a good support for serving a XHTML/HTML5 in web applications. In this chapter, you will learn in detail about Thymeleaf.
Thymeleaf converts your files into well-formed XML files. It contains 6 types of templates as given below −
XML
Valid XML
XHTML
Valid XHTML
HTML5
Legacy HTML5
All templates, except Legacy HTML5, are referring to well-formed valid XML files. Legacy HTML5 allows us to render the HTML5 tags in web page including not closed tags.
You can use Thymeleaf templates to create a web application in Spring Boot. You will have to follow the below steps to create a web application in Spring Boot by using Thymeleaf.
Use the following code to create a @Controller class file to redirect the Request URI to HTML file −
package com.tutorialspoint.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class WebController {
   @RequestMapping(value = "/index")
   public String index() {
      return "index";
   }
}
In the above example, the request URI is /index, and the control is redirected into the index.html file. Note that the index.html file should be placed under the templates directory and all JS and CSS files should be placed under the static directory in classpath. In the example shown, we used CSS file to change the color of the text.
You can use the following code and created a CSS file in separate folder css and name the file as styles.css −
h4 {
   color: red;
}

The code for index.html file is given below −
<!DOCTYPE html>
<html>
   <head>
      <meta charset = "ISO-8859-1" />
      <link href = "css/styles.css" rel = "stylesheet"/>
      <title>Spring Boot Application</title>
   </head>
   <body>
      <h4>Welcome to Thymeleaf Spring Boot web application</h4>
   </body>
</html>
The project explorer is shown in the screenshot given below −
Now, we need to add the Spring Boot Starter Thymeleaf dependency in our build configuration file.
Maven users can add the following dependency into the pom.xml file −
<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
Gradle users can add the following dependency in the build.gradle file −
compile group: 'org.springframework.boot', name: 'spring-boot-starter-thymeleaf'

The code for main Spring Boot application class file is given below −
package com.tutorialspoint.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(DemoApplication.class, args);
   }
}
The code for Maven – pom.xml is given below −
<?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.tutorialspoint</groupId>
   <artifactId>demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>demo</name>
   <description>Demo project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.8.RELEASE</version>
      <relativePath />
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</java.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-thymeleaf</artifactId>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
   
</project>
The code for Gradle – build.gradle is given below −
buildscript {
   ext {
      springBootVersion = '1.5.8.RELEASE'
   }
   repositories {
      mavenCentral()
   }
   dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
   }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

group = 'com.tutorialspoint'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
   mavenCentral()
}
dependencies {
   compile('org.springframework.boot:spring-boot-starter-web')
   compile group: 'org.springframework.boot', name: 'spring-boot-starter-thymeleaf'
   testCompile('org.springframework.boot:spring-boot-starter-test')
}
You can create an executable JAR file, and run the spring boot application by using the following Maven or Gradle commands −
For Maven, use the command as shown below −
mvn clean install

After “BUILD SUCCESS”, you can find the JAR file under the target directory.
For Gradle, use the command as shown below −
gradle clean build

After “BUILD SUCCESSFUL”, you can find the JAR file under the build/libs directory.
Run the JAR file by using the command given here −
java –jar <JARFILE> 

Now, the application has started on the Tomcat port 8080 as shown below −
Now hit the URL in your web browser and you can see the output as shown −