[JAVA] Use Thymeleaf with Azure Functions

I think that it is common to return JSON if it is serverless, but html can also be returned. So, without the template engine, creating html would be a pain, so I tried to use Thymeleaf.


Basically, it is a prerequisite that the environment is constructed according to the following. (It's ok if you're creating a project from a Maven archetype.) https://docs.microsoft.com/ja-jp/azure/azure-functions/functions-create-first-java-maven

First, an example of simply returning html


public class Function {
    public HttpResponseMessage<String> html(@HttpTrigger(name = "html", methods = {
            "get" }, authLevel = AuthorizationLevel.FUNCTION) HttpRequestMessage<String> req) {
        String html = "<html><head><title>Take it</title></head><body><h1>Bode</h1></body></html>";
        HttpResponseMessage<String> res = req.createResponse(200, html);
        res.addHeader("Content-Type", "text/html");

        return res;

Assemble the html by yourself and return it with HttpResponseMessage type. At this time, if you do not set Content-Type to text / html with addHeader, the browser will recognize it as just a character string.

It would be nice if the html is as simple as this, but when it gets complicated or dynamic elements come out, it will be painful, so I would like to use Thymeleaf.

Use Thymeleaf

First, add thymeleaf to the dependency of pom.xml. The version is up to date at this time.



Then the sauce.


public class Function{
    public HttpResponseMessage<String> thymeleaf(@HttpTrigger(name = "thymeleaf", methods = {
            "get" }, authLevel = AuthorizationLevel.FUNCTION) HttpRequestMessage<String> req) {
        ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();

        TemplateEngine templateEngine = new TemplateEngine();

        Context context = new Context();
        context.setVariable("message", "hogehoge");
        String html = templateEngine.process("test", context);

        HttpResponseMessage<String> res = req.createResponse(200, html);
        res.addHeader("Content-Type", "text/html");

        return res;

I usually use it with Spring, so I wasn't really aware of it, but there are several types of Template Resolver. This time, we will use ClassLoaderTemplateResolver.

Also, in order to pass the value to Thymeleaf side, it is necessary to create a Context object. I think it's like a Model in Spring.


<html xmlns:th="http://www.thymeleaf.org">
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <p th:text="${message}">Thymeleaf!!</p>

I made html like this. It is located in src / main / resources / template.

After that, you can start it, deploy it, and check the operation.


This time, Thymeleaf related instance is generated in the method, but it may be better to execute it in the constructor and make it an instance variable. However, it doesn't make sense if the constructor is executed every time it is accessed. If it is serverless, I do not understand the operation around here, so I think that I have to verify it someday.

Also, I feel that if you do so far, you should make it quickly with Spring Boot. If it's serverless, it has an Auto Scaling function, so it's a merit that you can take advantage of it.

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