Spring Boot and Thymeleaf Tutorial with Examples

What is Thymeleaf?
Create application
Thymeleaf Template
Static Resource & Properties File
Model, Form, Controller classes
Run the application

1. What is Thymeleaf?

Thymeleaf is a Java XML/XHTML/HTML5 Template Engine that can work both in web (Servlet-based) and non-web environments. It is better suited for serving XHTML/HTML5 at the view layer of MVC-based web applications, but it can process any XML file even in offline environments. It provides full Spring Framework integration.

The template file of Thymeleaf in essence are only a ordinary document file with the format of XML/XHTML/HTML5. Thymeleaf Engine will read a template file and combine with Java objects to generate another document.

Thymeleaf can be used to replace JSP on the View Layer of Web MVC application. Thymeleaf is open source code software, licensed under theApache 2.0.

Below is the image of the application that we will perform in this lesson:

See Also:
Thymeleaf Tutorials

2. Create application

On Eclipse, select:

File/New/Other...

Enter:

Name: SpringBootThymeleaf
Group: org.o7planning
Artifact: SpringBootThymeleaf
Description: Spring Boot and Thymeleaf
Package: org.o7planning.thymeleaf

Select 2 Web and Thymeleaf technologies.

Your Project has been created:

pom.xml

<?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>org.o7planning</groupId>
    <artifactId>SpringBootThymeleaf</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>SpringBootThymeleaf</name>
    <description>Spring Boot and Thymeleaf</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </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-thymeleaf</artifactId>
        </dependency>
        <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>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3. Thymeleaf Template

Thymeleaf Template is a template file. Its contents are in the XML/XHTML/HTML5 format. We will create 3 files and place it in the src/main/resources/templates folder:

index.html

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <meta charset="UTF-8" />
      <title>Welcome</title>
      <link rel="stylesheet" type="text/css" th:href="@{/css/style.css}"/>
   </head>
   <body>
      <h1>Welcome</h1>
      <h2 th:utext="${message}">..!..</h2>
      
      <!--  
      
         In Thymeleaf the equivalent of
         JSP's ${pageContext.request.contextPath}/edit.html
         would be @{/edit.html}
         
         -->
         
      <a th:href="@{/personList}">Person List</a>  
      
   </body>
   
</html>

personList.html

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <meta charset="UTF-8" />
      <title>Person List</title>
      <link rel="stylesheet" type="text/css" th:href="@{/css/style.css}"/>
   </head>
   <body>
      <h1>Person List</h1>
      <a href="addPerson">Add Person</a>
      <br/><br/>
      <div>
         <table border="1">
            <tr>
               <th>First Name</th>
               <th>Last Name</th>
            </tr>
            <tr th:each ="person : ${persons}">
               <td th:utext="${person.firstName}">...</td>
               <td th:utext="${person.lastName}">...</td>
            </tr>
         </table>
      </div>
   </body>
</html>

addPerson.html

<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
   <head>
      <meta charset="UTF-8" />
      <title>Add Person</title>
      <link rel="stylesheet" type="text/css" th:href="@{/css/style.css}"/>
   </head>
   <body>
      <h1>Create a Person:</h1>
      
      <!--  
         In Thymeleaf the equivalent of
         JSP's ${pageContext.request.contextPath}/edit.html
         would be @{/edit.html}         
         -->
         
      <form th:action="@{/addPerson}"
         th:object="${personForm}" method="POST">
         First Name:
         <input type="text" th:field="*{firstName}" />    
         <br/>
         Last Name:
         <input type="text" th:field="*{lastName}" />     
         <br/>
         <input type="submit" value="Create" />
      </form>
      
      <br/>
      
      <!-- Check if errorMessage is not null and not empty -->
      
      <div th:if="${errorMessage}" th:utext="${errorMessage}"
         style="color:red;font-style:italic;">
         ...
      </div>
      
   </body>
</html>

I have created 3 HTML files above. The above HTML files need to be appropriate to the standards of XML. All tags must have open and close, for example:

<div>A div tag</div>

<br />

<meta charset="UTF-8" />

All HTML files need declaring use of Thymeleaf Namespace:

<!-- Thymeleaf Namespace -->

<html xmlns:th="http://www.thymeleaf.org">

In template files, there are Thymeleaf Markers (markers of Thymeleaf) which are instructions helping Thymeleaf Engine process data.
Thymeleaf Engine analyses template files and combines them with Java data to generate a new document.

Below are examples to use the Context-Path in the Thymeleaf:

<!-- Example 1:  -->

<a th:href="@{/mypath/abc.html}">A Link</a>

Output: ==>

<a href="/my-context-path/mypath/abc.html">A Link</a>


<!-- Example 2:  -->

<form th:action="@{/mypath/abc.html}"
          th:object="${personForm}" method="POST">

Output: ==>

<form action="/my-context-path/mypath/abc.html"  method="POST">

4. Static Resource & Properties File

For Static Resources, for example, css, javascript, image files,.. you need to put them into src/main/resources/static folder or its subfolders.

style.css

h1 {
    color:#0000FF;
}

h2 {
    color:#FF0000;
}

table {
    border-collapse: collapse;
}

table th, table td {
    padding: 5px;
}

application.properties

spring.thymeleaf.cache=false

welcome.message=Hello Thymeleaf
error.message=First Name & Last Name is required!

5. Model, Form, Controller classes

Person.java

package org.o7planning.thymeleaf.model;

public class Person {

    private String firstName;
    private String lastName;

    public Person() {

    }

    public Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

}

PersonForm classrepresents for the data ofFORM when you create a new Person on addPerson page..

PersonForm.java

package org.o7planning.thymeleaf.form;
 

public class PersonForm {

    private String firstName;
    private String lastName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    
}

MainController is a controller class. It processes a user's requests and controls the flow of the application.

MainController.java

package org.o7planning.thymeleaf.controller;

import java.util.ArrayList;
import java.util.List;

import org.o7planning.thymeleaf.form.PersonForm;
import org.o7planning.thymeleaf.model.Person;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class MainController {

	private static List<Person> persons = new ArrayList<Person>();

	static {
		persons.add(new Person("Bill", "Gates"));
		persons.add(new Person("Steve", "Jobs"));
	}

	// Inject via application.properties
	@Value("${welcome.message}")
	private String message;

	@Value("${error.message}")
	private String errorMessage;

	@RequestMapping(value = { "/", "/index" }, method = RequestMethod.GET)
	public String index(Model model) {

		model.addAttribute("message", message);

		return "index";
	}

	@RequestMapping(value = { "/personList" }, method = RequestMethod.GET)
	public String personList(Model model) {

		model.addAttribute("persons", persons);

		return "personList";
	}

	@RequestMapping(value = { "/addPerson" }, method = RequestMethod.GET)
	public String showAddPersonPage(Model model) {

		PersonForm personForm = new PersonForm();
		model.addAttribute("personForm", personForm);

		return "addPerson";
	}

	@RequestMapping(value = { "/addPerson" }, method = RequestMethod.POST)
	public String savePerson(Model model, //
			@ModelAttribute("personForm") PersonForm personForm) {

		String firstName = personForm.getFirstName();
		String lastName = personForm.getLastName();

		if (firstName != null && firstName.length() > 0 //
				&& lastName != null && lastName.length() > 0) {
			Person newPerson = new Person(firstName, lastName);
			persons.add(newPerson);

			return "redirect:/personList";
		}

		model.addAttribute("errorMessage", errorMessage);
		return "addPerson";
	}

}