Thymeleaf - Quick Reference
Deep Knowledge: Use mcp__documentation__fetch_docs with technology: thymeleaf for comprehensive documentation.
Pattern Essenziali
Basic Syntax
<!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org"> <head> <title th:text="${title}">Default</title> </head> <body> <h1 th:text="${message}">Hello</h1> <p th:text="'Welcome, ' + ${name}">Welcome, User</p> </body> </html>
Variables & Loops
<!-- Variable --> <p th:text="${user.name}">Name</p>
<!-- Loop --> <tr th:each="user : ${users}"> <td th:text="${user.name}">Name</td> <td th:text="${user.email}">Email</td> </tr>
<!-- Conditionals --> <p th:if="${user.active}">Active</p> <p th:unless="${user.active}">Inactive</p>
Email Service
@Service @RequiredArgsConstructor public class EmailService {
private final TemplateEngine templateEngine;
private final JavaMailSender mailSender;
public void sendWelcome(User user) {
Context ctx = new Context();
ctx.setVariable("userName", user.getName());
ctx.setVariable("actionUrl", "https://app.com/verify");
String html = templateEngine.process("emails/welcome", ctx);
MimeMessage msg = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(msg, true);
helper.setTo(user.getEmail());
helper.setSubject("Welcome!");
helper.setText(html, true);
mailSender.send(msg);
}
}
Fragments & Layouts
<!-- fragments/common.html --> <nav th:fragment="navigation"> <ul> <li><a th:href="@{/}">Home</a></li> <li><a th:href="@{/about}">About</a></li> </ul> </nav>
<footer th:fragment="footer(year)"> <p th:text="'© ' + ${year} + ' My Company'">© 2024 My Company</p> </footer>
<!-- Usage: th:replace vs th:insert --> <!-- th:replace - replaces host tag completely --> <div th:replace="~{fragments/common :: navigation}"></div>
<!-- th:insert - inserts fragment inside host tag --> <div th:insert="~{fragments/common :: navigation}"></div>
<!-- With parameters --> <div th:replace="~{fragments/common :: footer(${#dates.year(#dates.createNow())})}"></div>
Layout Dialect
<!-- pom.xml --> <dependency> <groupId>nz.net.ultraq.thymeleaf</groupId> <artifactId>thymeleaf-layout-dialect</artifactId> </dependency>
<!-- layouts/main.html --> <!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org" xmlns:layout="http://www.ultraq.net.nz/thymeleaf/layout"> <head> <title layout:title-pattern="$CONTENT_TITLE - $LAYOUT_TITLE">My App</title> <link rel="stylesheet" th:href="@{/css/main.css}"/> </head> <body> <header th:replace="~{fragments/common :: navigation}"></header>
<main layout:fragment="content">
<!-- Page content goes here -->
</main>
<footer th:replace="~{fragments/common :: footer}"></footer>
<script layout:fragment="scripts"></script>
</body> </html>
<!-- pages/home.html --> <!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org" xmlns:layout="http://www.ultraq.net.nz/thymeleaf/layout" layout:decorate="~{layouts/main}"> <head> <title>Home</title> </head> <body> <main layout:fragment="content"> <h1>Welcome!</h1> <p th:text="${message}">Content</p> </main>
<th:block layout:fragment="scripts">
<script th:src="@{/js/home.js}"></script>
</th:block>
</body> </html>
Form Binding
<form th:action="@{/users}" th:object="${userForm}" method="post"> <div> <label for="name">Name:</label> <input type="text" id="name" th:field="{name}" th:classappend="${#fields.hasErrors('name')} ? 'error' : ''"/> <span th:if="${#fields.hasErrors('name')}" th:errors="{name}" class="error-msg">Name error</span> </div>
<div>
<label for="email">Email:</label>
<input type="email" id="email" th:field="*{email}"/>
<span th:if="${#fields.hasErrors('email')}"
th:errors="*{email}" class="error-msg">Email error</span>
</div>
<div>
<label for="role">Role:</label>
<select id="role" th:field="*{role}">
<option value="">-- Select --</option>
<option th:each="role : ${roles}"
th:value="${role}"
th:text="${role.displayName}">Role</option>
</select>
</div>
<button type="submit">Save</button>
</form>
JavaScript Inlining
<script th:inline="javascript"> // Natural templates with fallback const user = /[[${user}]]/ { name: 'default' }; const userId = /[[${user.id}]]/ 0; const isAdmin = /[[${user.admin}]]/ false;
// Array
const items = /*[[${items}]]*/ [];
// Conditional in JS
/*[# th:if="${user != null}"]*/
console.log('User:', user.name);
/*[/]*/
</script>
<!-- CSS inlining --> <style th:inline="css"> .user-bg { background-color: [[${user.favoriteColor}]]; } </style>
Utility Objects
<!-- Dates --> <p th:text="${#dates.format(user.createdAt, 'dd/MM/yyyy HH:mm')}">Date</p> <p th:text="${#dates.dayOfWeekName(date)}">Monday</p>
<!-- Strings --> <p th:text="${#strings.toUpperCase(name)}">NAME</p> <p th:text="${#strings.abbreviate(text, 100)}">Truncated...</p> <p th:text="${#strings.isEmpty(value) ? 'N/A' : value}">Value</p> <p th:text="${#strings.listJoin(items, ', ')}">a, b, c</p>
<!-- Numbers --> <p th:text="${#numbers.formatDecimal(price, 1, 2)}">10.50</p> <p th:text="${#numbers.formatCurrency(amount)}">$1,234.56</p>
<!-- Lists --> <p th:text="${#lists.size(users)}">Count</p> <p th:if="${#lists.isEmpty(users)}">No users</p> <p th:text="${#lists.contains(roles, 'ADMIN')}">Has admin</p>
<!-- Aggregates --> <p th:text="${#aggregates.sum(prices)}">Total</p> <p th:text="${#aggregates.avg(scores)}">Average</p>
Switch/Case
<div th:switch="${user.role}"> <p th:case="'ADMIN'">Administrator</p> <p th:case="'MANAGER'">Manager</p> <p th:case="'USER'">Regular User</p> <p th:case="*">Unknown Role</p> </div>
Iteration Status
<tr th:each="user, stat : ${users}" th:class="${stat.odd} ? 'odd' : 'even'"> <td th:text="${stat.index}">0</td> <td th:text="${stat.count}">1</td> <td th:text="${user.name}">Name</td> <td th:if="${stat.first}">First!</td> <td th:if="${stat.last}">Last!</td> </tr>
Expressions
Expr Uso
${var}
Variable
*{prop}
Selection (con th:object)
@{/url}
Link URL
#{msg}
Message i18n
~{frag}
Fragment
Best Practices
Do Don't
Use th:text for escaped output Use th:utext with user input (XSS)
Use fragments for reusable components Duplicate HTML across templates
Keep templates simple Put complex logic in templates
Use i18n messages Hardcode text strings
Use layout dialects Repeat layout in every page
When NOT to Use This Skill
-
REST APIs - Use spring-rest skill for JSON responses
-
SPA frontends - Use React, Vue, or Angular
-
PDF reports - Use JasperReports or iText
-
High-traffic APIs - Consider static frontends
Anti-Patterns
Anti-Pattern Problem Solution
th:utext with user input XSS vulnerability Use th:text for escaping
Complex logic in templates Hard to test, maintain Move logic to controller
Missing th namespace Silent failures Always declare xmlns:th
Inline styles everywhere Inconsistent UI Use CSS classes
No fragment reuse Code duplication Extract common fragments
Quick Troubleshooting
Problem Diagnostic Fix
Variables not rendering Check th: prefix Use th:text, th:value
Template not found Check path Place in templates/ folder
Iteration not working Check th:each syntax Verify collection is passed
Fragments not included Check path syntax Use ~{fragments/name :: fragment}
i18n not working Check messages.properties Verify file location and keys
Reference Documentation
-
Thymeleaf Docs
-
Spring + Thymeleaf