How to create a Spring Boot Thymeleaf web application

In this article, I will be demonstrating creating a Spring Boot Thymeleaf web application.

Project Creation and Setup

Step 1 – Create a new Maven Project (Refer to this blog post). This should create a project as shown below:

Step 2 – Add the Spring Boot and Thymeleaf dependency. So, the pom.xml file should be similar to the following:

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">  <modelVersion>4.0.0</modelVersion>  <groupId>com.learnjava</groupId>  <artifactId>learnjava-springbootthymeleaf-demo</artifactId>  <version>0.0.1-SNAPSHOT</version>  <parent>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-parent</artifactId>    <version>2.1.2.RELEASE</version>  </parent>  <dependencies>    <dependency>      <groupId>org.springframework.boot</groupId>      <artifactId>spring-boot-starter-web</artifactId>    </dependency>    <dependency>      <groupId>org.springframework.boot</groupId>      <artifactId>spring-boot-starter-thymeleaf</artifactId>    </dependency>  </dependencies></project>

Writing Simple Code

Step 3 – Creating a Controller class

Let us first create a simple controller that displays a static html page without any data:

package com.learnjava.springbootthymeleafdemo.welcome;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.GetMapping;@Controllerpublic class WelcomeController {  @GetMapping("/")  public String showHome() {    return "home";  }}
  • The WelcomeController class has the @Controller annotation. This designates the class as an MVC controller.
  • It has a showHomemethod.  The GetMapping annotation specifies that this maps to the “/” path.
  • It simply returns the String hello. This specifies the name of the Thymeleaf template (an html file) that needs to be displayed.

Step 4 – Creating the Thymeleaf template file

As seen earlier, the controller returns the name of the Thymeleaf template.  An HTML file with this name needs to be present in a templates folder within the src/main/resources folder. So, we need to create home.html within the src/main/resources/templates folder as follows:

<!DOCTYPE html><html>   <head>      <title>LearnJava Spring Boot Application</title>       <link href = "css/style.css" rel = "stylesheet"/>   </head>   <body>      <h2>Welcome to LearnJava!</h2>   </body></html>
  • This is a simple html file that displays a message
  • It references the style.css.

Step 5 – Creating CSS file

The Thymeleaf template can optionally refer a CSS file as done above. In such cases, the specified CSS file needs to be present in a static folder within the src/main/resources folder. So, we need to create style.css within the src/main/resources/static folder as follows:

h2 {   color: blue;}
  • This is a simple CSS file that displays H2 headings in blue colour.

Running the application

Step 6 – Run Main.java as a Java application as shown below:

 

Step 7 – Open http://localhost:8080/ in browser. This displays the following output:

 

Some More Code

Most real-world applications require to do more complex things than display a simple message. Let us write some more code that displays data in a tabular form.

Step 8 – Create a Book class as follows:

public class Book {  private int id;  private String name;  private String author;     // constructor, getters and setters}
  • The Book class has fields corresponding to id, nameand author

Step 9 – Create a BookController class as follows:

import java.util.ArrayList;import java.util.List;import org.springframework.beans.factory.annotation.Value;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.GetMapping;@Controllerpublic class BookController {    @Value("${greeting}")  private String greeting;     @GetMapping("/books")    public String getAllBooks(Model model){      //Returns hardcoded data, a real world application would return from the database      List<Book> books = new ArrayList<Book>();      books.add(new Book(1,"Emma", "Jane Austen"));      books.add(new Book(2,"Harry Potter", "JK Rowling"));      books.add(new Book(3,"The Partner", "John Grisham"));      model.addAttribute("books", books);      model.addAttribute("greeting",greeting);      return "books";    } }
  • The BookController class has a greetingfield. It has the @Value annotation with the value $greeting. This value can be set in the application.properties file as explained below.
  • The BookController class also has a getAllBooksmethod.  This maps to the “/books” path as specified via the GetMapping annotation.
  • It accepts a Model object as a parameter. In Spring, A Model represents the data to be sent to the front-end.
  • Next, the getAllBooksmethod creates a List of Book objects and sets it as a Model attribute. In a typical Spring Boot application, data is retrieved via Spring Data JPA as demonstrated here.
  • Similarly, it also sets the greeting field as a Model attribute.
  • Thus, any data that needs to be sent to the HTML template, needs to be set as as model attribute like this.
  • Finally, it returns the String books. This specifies the name of the Thymeleaf template.

Step 10 – Defining a greeting property

The BookController class has a greeting field. The @Value annotation assigns it a value via $greeting. Such properties need to be defined in an  application.properties file within the src/main/resources folder. So, we need to create src/main/resources/application.properties as follows:

greeting=Hello!

Step 11 – Creating books.html

Just like home.html, we need to create books.html within the src/main/resources/templates folder as follows:

<html><head><title>Book</title></head><body><H2> <p th:text="${greeting}"></p></H2><table>  <thead>    <tr>      <th>Book Id</th>      <th>Book Name</th>      <th>Book Author</th>    </tr>  </thead>  <tbody>    <tr th:each="book : ${books}">      <td th:text="${book.id}"></td>      <td th:text="${book.name}"></td>      <td th:text="${book.author}"></td>    </tr>  </tbody></table></body></html>
  • th:text is used to refer to the $greeting value
  • th:each is used to iterate through the books list
  • th:text is used to obtain the value of each book field

Step 12 – Run the application and type http://localhost:8080/books in a browser. This displays the following output:

You can download the complete source code from the GitHub Repository here.

Further Learning

Mastering Thymeleaf with Spring Boot
Spring Boot Tutorial for beginners
Spring Boot Fundamentals
Spring 5 with Spring Boot

Conclusion

So, in this article, we learnt how to create a simple Spring Boot Thymeleaf application.

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