Using Thymeleaf when the value is null

java

null-safe-operator

thymeleaf-best-practices

spring-standard-dialect

byAlex Kataev·Oct 25, 2024

To deal with null values in Thymeleaf, you can use the Elvis operator:

<!--Elvis has entered the building, ready to handle nulls!-->
<span th:text="${value} ?: 'Default text'"></span>

If value is null, "Default text" is displayed. For conditional display, use th:if/th:unless:

<!--I see the value! Let's display it.-->
<span th:if="${value}" th:text="${value}"></span>
<!--Whoops, the value is on a vacation (null), let's use the default text.-->
<span th:unless="${value}" th:text="'Default text'"></span>

These snippets allow you to manage null values effectively in Thymeleaf templates.

Using null-safe operator in Thymeleaf

For cases where you want to access attributes of an object that might be null, use the null-safe (?) operator:

<!-- Hello, do you have a name?-->
<span th:text="${user?.name}"></span>

If the user object is null, no NullPointerException is thrown. Don't forget the importance of using the SpringStandardDialect. If you are using Thymeleaf without Spring MVC, you'll need to set this dialect manually:

// Now we're speaking the same dialect!
templateEngine.setDialect(new SpringStandardDialect());

Harnessing utility methods for defaults

When it comes to dealing with null values, the ${#objects.nullSafe(obj, default)} utility method is your go-to tool:

<!-- Everyone is a guest until proven a user! -->
<span th:text="${#objects.nullSafe(user, 'Guest')}"></span>

If user is null, Thymeleaf will display "Guest". This tool is handy for setting up fallback values.

Null management in forms and user inputs

When dealing with forms and inputs, where null values might cause issues, you can combine th:value with th:attr:

<!-- Name? Who needs a name? (Default to 'Enter your name'.) -->
<input type="text" th:value="${user?.name}" th:attr="placeholder=${user?.name ?: 'Enter your name'}"/>

This avoids potential errors when mapping form fields to objects that may have null properties.

Towards a null-resilient code

While Thymeleaf provides great tools to handle null values, avoid overusing null checks in your templates. The best practice is to strongly design your application logic to minimize the occurrence of nulls in the first place.