cloudflightio / htmx-spring-boot-thymeleaf

Spring Boot and Thymeleaf helpers for working with htmx

Spring Boot and Thymeleaf library for htmx

This project provides annotations, helper classes and a Thymeleaf dialect to make it easy to work with htmx in a Spring Boot application.

More information about htmx can be viewed on their website.

Maven configuration

The project provides the following libraries, which are available on Maven Central, so it is easy to add the desired dependency to your project.

htmx-spring-boot

Provides annotations and helper classes.

<dependency>
    <groupId>io.github.wimdeblauwe</groupId>
    <artifactId>htmx-spring-boot</artifactId>
    <version>LATEST_VERSION_HERE</version>
</dependency>

htmx-spring-boot-thymeleaf

Provides a Thymeleaf dialect to easily work with htmx attributes.

<dependency>
    <groupId>io.github.wimdeblauwe</groupId>
    <artifactId>htmx-spring-boot-thymeleaf</artifactId>
    <version>LATEST_VERSION_HERE</version>
</dependency>

Usage

Configuration

The included Spring Boot Auto-configuration will enable the htmx integrations.

Request Headers

See Request Headers Reference for the related htmx documentation.

Methods can be annotated with @HxRequest to be selected when an htmx-based request (ie hx-get) is made.

@GetMapping("/users")
@HxRequest                  // Called when hx-get request to '/users/' is made 
public String htmxRequest(HtmxRequest details){
    service.doSomething(details);

    return "partial";
}

@GetMapping("/users")        // Only called on a full page refresh, not an htmx request
public String normalRequest(HtmxRequest details){
    service.doSomething(details);

    return "users";
}

These annotations allow for composition if you wish to combine them, so you could combine annotations to make a custom @HxGetMapping.

Using HtmxRequest to inspect HTML request headers

The HtmxRequest object can be injected into controller methods to check the various htmx request headers.

@GetMapping
@ResponseBody
public String htmxRequestDetails(HtmxRequest htmxReq) { // HtmxRequest is injected
    if(htmxReq.isHistoryRestoreRequest()){
        // ...
    }

    return "";
}

Response Headers

See Response Headers Reference for the related htmx documentation.

Setting the hx-trigger header triggers an event when the response is swapped in by htmx. The @HxTrigger annotation supports doing that for you:

@GetMapping("/users")
@HxRequest
@HxTrigger("userUpdated") // 'userUpdated' event will be triggered by htmx
public String hxUpdateUser(){
    return "users";
}

OOB Swap support

htmx supports updating multiple targets by returning multiple partials in a single response with hx-swap-oob. Return partials using this library use the HtmxResponse as a return type:

@GetMapping("/partials/main-and-partial")
public HtmxResponse getMainAndPartial(Model model){
    model.addAttribute("userCount", 5);
    return new HtmxResponse()
        .addTemplate("users :: list")
        .addTemplate("users :: count");
}

An HtmxResponse can be formed from view names, as above, or fully resolved View instances, if the controller knows how to do that, or from ModelAndView instances (resolved or unresolved). For example:

@GetMapping("/partials/main-and-partial")
public HtmxResponse getMainAndPartial(Model model){
    return new HtmxResponse()
        .addTemplate(new ModelAndView("users :: list")
        .addTemplate(new ModelAndView("users :: count", Map.of("userCount",5));
}

Using ModelAndView means that each fragment can have its own model (which is merged with the controller model before rendering).

Spring Security

The library has an HxRefreshHeaderAuthenticationEntryPoint that you can use to have htmx force a full page browser refresh in case there is an authentication failure. If you don't use this, then your login page might be appearing in place of a swap you want to do somewhere. See htmx-authentication-error-handling blog post for detailed information.

To use it, add it to your security configuration like this:

@Bean
public SecurityFilterChain filterChain(HttpSecurity http)throws Exception{
    // probably some other configurations here

    var entryPoint = new HxRefreshHeaderAuthenticationEntryPoint();
    var requestMatcher = new RequestHeaderRequestMatcher("HX-Request");
    http.exceptionHandling(exception ->
        exception.defaultAuthenticationEntryPointFor(entryPoint, requestMatcher));
    return http.build();
}

Thymeleaf

See Attribute Reference for the related htmx documentation.

The Thymeleaf dialect has appropriate processors that enable Thymeleaf to perform calculations and expressions in htmx-related attributes.

Note The : colon instead of the typical hyphen.

• hx:get: This is a Thymeleaf processing enabled attribute
• hx-get: This is just a static attribute if you don't need the Thymeleaf processing

For example, this Thymeleaf template:

<div hx:get="@{/users/{id}(id=${userId})}" hx-target="#otherElement">Load user details</div>

Will be rendered as:

<div hx-get="/users/123" hx-target="#otherElement">Load user details</div>

The Thymeleaf dialect has corresponding processors for most of the hx-* attributes. Please open an issue if something is missing.

Note Be careful about using # in the value. If you do hx:target="#mydiv", then this will not work as Thymeleaf uses the # symbol for translation keys. Either use hx-target="#mydiv" or hx:target="${'#mydiv'}"

Map support for hx:vals

The hx-vals attribute allows to add to the parameters that will be submitted with the AJAX request. The value of the attribute should be a JSON string.

The library makes it a bit easier to write such a JSON string by adding support for inline maps.

For example, this Thymeleaf expression:

<div hx:vals="${ {id: user.id } }"></div>

will render as:

<div hx-vals="{&amp;quot;id&amp;quot;: 1234 }"></div>

(Given user.id has the value 1234)

Articles

Links to articles and blog posts about this library:

• Release 1.0.0 and 2.0.0 of htmx-spring-boot-thymeleaf
• Htmx authentication error handling
• Thymeleaf and htmx with out of band swaps

Spring Boot compatibility

Library version	Spring Boot	Minimum Java version
3.0.0	3.1.x	17
2.2.0	3.0.x	17
1.0.0	2.7.x	11

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

Apache 2.0

Release

To release a new version of the project, follow these steps:

1. Update pom.xml with the new version (Use mvn versions:set -DgenerateBackupPoms=false -DnewVersion=<VERSION>)
2. Commit the changes locally.
3. Tag the commit with the version (e.g. 1.0.0) and push the tag.
4. Create a new release in GitHub via https://github.com/wimdeblauwe/htmx-spring-boot/releases/new
   • Select the newly pushed tag
   • Update the release notes. This should automatically start the release action.
5. Update pom.xml again with the next SNAPSHOT version.
6. Close the milestone in the GitHub issue tracker.