1. Overview
In this tutorial, we’ll show how to make use of Thymeleaf Fragments to reuse some common parts of a site. After setting up a very simple Spring MVC project, we’ll focus on views.
If you’re new to Thymeleaf, you can check other articles on this site like this introduction, as well as this one about the 3.0 version of the engine.
2. Maven Dependencies
We’ll need a couple of dependencies to enable Thymeleaf:
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf</artifactId>
<version>3.1.2.RELEASE</version>
</dependency>
<dependency>
<groupId>org.thymeleaf</groupId>
<artifactId>thymeleaf-spring5</artifactId>
<version>3.1.2.RELEASE</version>
</dependency>
The latest version of thymeleaf and thymeleaf-spring5 can be found on Maven Central.
3. Spring Project
3.1. Spring MVC Configuration
To enable Thymeleaf and set the template suffix, we need to configure MVC with a view resolver and template resolver.
We’ll also set the directory for some static resources:
@Bean
public ViewResolver htmlViewResolver() {
ThymeleafViewResolver resolver = new ThymeleafViewResolver();
resolver.setTemplateEngine(templateEngine(htmlTemplateResolver()));
resolver.setContentType("text/html");
resolver.setCharacterEncoding("UTF-8");
resolver.setViewNames(ArrayUtil.array("*.html"));
return resolver;
}
private ITemplateResolver htmlTemplateResolver() {
SpringResourceTemplateResolver resolver
= new SpringResourceTemplateResolver();
resolver.setApplicationContext(applicationContext);
resolver.setPrefix("/WEB-INF/views/");
resolver.setCacheable(false);
resolver.setTemplateMode(TemplateMode.HTML);
return resolver;
}
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/resources/**", "/css/**")
.addResourceLocations("/WEB-INF/resources/", "/WEB-INF/css/");
}
Note that if we’re using Spring Boot, this configuration may not be necessary unless we need to apply our own customizations.
3.2. The Controller
In this case, the controller is just a vehicle for the views. Each view shows a different fragment use scenario.
The last one loads some data that is passed through the model to be displayed on the view:
@Controller
public class FragmentsController {
@GetMapping("/fragments")
public String getHome() {
return "fragments.html";
}
@GetMapping("/markup")
public String markupPage() {
return "markup.html";
}
@GetMapping("/params")
public String paramsPage() {
return "params.html";
}
@GetMapping("/other")
public String otherPage(Model model) {
model.addAttribute("data", StudentUtils.buildStudents());
return "other.html";
}
}
Note that the view names must contain the “.html” suffix because of the way we configured our resolver. We’ll also specify the suffix when we refer to fragment names.
4. The Views
4.1. Simple Fragment Inclusion
First of all, we’ll use reuse common parts in our pages.
We can define these parts as fragments, either in isolated files or in a common page. In this project, these reusable parts are defined in a folder named fragments.
There are three basic ways to include content from a fragment:
- insert – inserts content inside the tag
- replace – replaces the current tag with the tag defining the fragment
- include – this is deprecated but it may still appear in a legacy code
The next example, fragments.html, shows the use of all three ways. This Thymeleaf template adds fragments in the head and the body of the document:
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head>
<title>Thymeleaf Fragments: home</title>
<!--/*/ <th:block th:include="fragments/general.html :: headerfiles">
</th:block> /*/-->
</head>
<body>
<header th:insert="fragments/general.html :: header"> </header>
<p>Go to the next page to see fragments in action</p>
<div th:replace="fragments/general.html :: footer"></div>
</body>
</html>
Now, let’s take a look at a page that holds some fragments. It’s called general.html, and it’s like a whole page with some parts defined as fragments ready to be used:
<!DOCTYPE HTML>
<html xmlns:th="http://www.thymeleaf.org">
<head th:fragment="headerfiles">
<meta charset="UTF-8" />
<link th:href="@{/css/styles.css}" rel="stylesheet">
</head>
<body>
<div th:fragment="header">
<h1>Thymeleaf Fragments sample</h1>
</div>
<p>Go to the next page to see fragments in action</p>
<aside>
<div>This is a sidebar</div>
</aside>
<div class="another">This is another sidebar</div>
<footer th:fragment="footer">
<a th:href="@{/fragments}">Fragments Index</a> |
<a th:href="@{/markup}">Markup inclussion</a> |
<a th:href="@{/params}">Fragment params</a> |
<a th:href="@{/other}">Other</a>
</footer>
</body>
</html>
The section contains just a stylesheet, but we could apply other tools such as Bootstrap, jQuery, or Foundation, either directly or using Webjars.
Note that all the reusable tags of this template have the attribute th:fragment, but next we’ll see how to include any other part of the page.
After the rendering and fragments inclusion, the returned content is:
<!DOCTYPE HTML>
<html>
<head>
<title>Thymeleaf Fragments: home</title>
<meta charset="UTF-8" />
<link href="/spring-thymeleaf/css/styles.css" rel="stylesheet">
</head>
<body>
<header>
<div>
<h1>Thymeleaf Fragments sample</h1>
</div>
</header>
<p>Go to the next page to see fragments in action</p>
<footer>
<a href="/spring-thymeleaf/fragments">Fragments Index</a> |
<a href="/spring-thymeleaf/markup">Markup inclussion</a> |
<a href="/spring-thymeleaf/params">Fragment params</a> |
<a href="/spring-thymeleaf/other">Other</a>
</footer>
</body>
</html>
4.2. Markup Selectors for Fragments
One of the great things about Thymeleaf Fragments is that we can also grab any part of a template just using the simple selectors, through classes, ids, or simply by tags.
This page, for example, includes some components from general.html file: an aside block and the div.another block:
<body>
<header th:insert="fragments/general.html :: header"> </header>
<div th:replace="fragments/general.html :: aside"></div>
<div th:replace="fragments/general.html :: div.another"></div>
<div th:replace="fragments/general.html :: footer"></div>
</body>
4.3. Parametrized Fragments
We can pass parameters to a fragment in order to change some specific part of it. To do that, the fragment must be defined as a function call, where we must declare a list of parameters.
In this example, we define a fragment for a generic form field:
<div th:fragment="formField (field, value, size)">
<div>
<label th:for="${#strings.toLowerCase(field)}"> <span
th:text="${field}">Field</span>
</label>
</div>
<div>
<input type="text" th:id="${#strings.toLowerCase(field)}"
th:name="${#strings.toLowerCase(field)}" th:value="${value}"
th:size="${size}">
</div>
</div>
And here’s a simple use of that fragment where we pass parameters to it:
<body>
<header th:insert="fragments/general.html :: header"> </header>
<div th:replace="fragments/forms.html
:: formField(field='Name', value='John Doe',size='40')">
</div>
<div th:replace="fragments/general.html :: footer"></div>
</body>
And this is how the returned field will look:
<div>
<div>
<label for="name"> <span>Name</span>
</label>
</div>
<div>
<input type="text" id="name"
name="name" value="John Doe"
size="40">
</div>
</div>
4.4. Fragment Inclusion Expressions
Thymeleaf fragments offer other interesting options such as support for conditional expressions to determine whether to include a fragment.
Using the Elvis operator with any of the expressions provided by Thymeleaf (security, strings, and collections for example), we’re able to load different fragments.
For example, we can define this fragment with some content that we’ll show depending on a given condition. This could be a file containing different kinds of blocks:
<div th:fragment="dataPresent">Data received</div>
<div th:fragment="noData">No data</div>
And this is how we could load them with an expression:
<div
th:replace="${#lists.size(data) > 0} ?
~{fragments/menus.html :: dataPresent} :
~{fragments/menus.html :: noData}">
</div>
To learn more about Thymeleaf Expressions, check our article here.
4.5. Flexible Layouts
The next example also shows two other interesting uses of fragments to render a table with data. This is the reusable table fragment, with two important parts: a table header that can be changed, and the body where data is rendered:
<table>
<thead th:fragment="fields(theadFields)">
<tr th:replace="${theadFields}">
</tr>
</thead>
<tbody th:fragment="tableBody(tableData)">
<tr th:each="row: ${tableData}">
<td th:text="${row.id}">0</td>
<td th:text="${row.name}">Name</td>
</tr>
</tbody>
<tfoot>
</tfoot>
</table>
When we want to use this table, we can pass our own table header using the fields function. The header is referenced with the class myFields. The table body is loaded by passing data as a parameter to the tableBody function:
<body>
<header th:replace="fragments/general.html :: header"> </header>
<table>
<thead th:replace="fragments/tables.html
:: fields(~{ :: .myFields})">
<tr class="myFields">
<th>Id</th>
<th>Name</th>
</tr>
</thead>
<div th:replace="fragments/tables.html
:: tableBody(tableData=${data})">
</div>
</table>
<div th:replace="fragments/general.html :: footer"></div>
</body>
And this is how the final page will look:
<body>
<div>
<h1>Thymeleaf Fragments sample</h1>
</div>
<div>Data received</div>
<table>
<thead>
<tr class="myFields">
<th>Id</th>
<th>Name</th>
</tr>
</thead>
<tbody>
<tr>
<td>1001</td>
<td>John Smith</td>
</tr>
<tr>
<td>1002</td>
<td>Jane Williams</td>
</tr>
</tbody>
</table>
<footer>
<a href="/spring-thymeleaf/fragments">Fragments Index</a> |
<a href="/spring-thymeleaf/markup">Markup inclussion</a> |
<a href="/spring-thymeleaf/params">Fragment params</a> |
<a href="/spring-thymeleaf/other">Other</a>
</footer>
</body>
5. Conclusion
In this article, we’ve shown how to reuse view components through the use of Thymeleaf Fragments, a powerful tool that can make template management easier.
We have also presented some other interesting features that go beyond the basics. We should take these into account when choosing Thymeleaf as our view rendering engine.
If you want to learn about other Thymeleaf features, you should definitely take a look at our article about Layout Dialects.
As always, the complete implementation code of the example is available over on GitHub.