Javalin: Trouble understanding how to use the templating engines in Javalin?

[Schachte]

I'm reading through the docs and looking online and struggling to use any of the templating engines like markdown or freemarker. I do not have a renderThymeLeaf or similar functions available on my context object. How is this supposed to be configured?

[Schachte]

I'm reading the unit tests right now. Do I actually need to do anything to get the interpolation to work?

https://github.com/tipsy/javalin/blob/e8aee2a43f6b7e67e19d87bcc234afd1210aa38c/src/test/java/io/javalin/TestTemplates.kt#L71

[tipsy]

It should just be render(path, model). The suffixes were removed in 2.0, it finds the correct engine based on the file extension. Where did you find the outdated example?

[Schachte]

Hm, must have been linked on outdated docs somehow. Is it possible (if I'm not doing templating) to just return a standard html file from the resources dir?

[tipsy]

Yes, you can use a static resource handler for that: https://javalin.io/documentation#static-files

[Schachte]

@tipsy I'm ultimately just looking to do something along the lines of context.render("file.html");

[tipsy]

That seems a bit odd, but you can register a .html FileRenderer which just reads the file:

JavalinRenderer.register(FileRenderer { path, model -> 
    String(Files.readAllBytes(Paths.get(path)))
}, ".html")

[Schachte]

hmm. I must be doing something wrong, I have the following:

    JavalinRenderer.register(
        (String path, Map<String, Object> model) -> {
          try {
            return new String(Files.readAllBytes(Paths.get(path)));
          } catch (IOException e) {
            return null;
          }
        },
        ".html");

    app.get("/", redirectHandler);

then

Handler

context.render("AuthenticationSuccess.html");

or

context.render("AuthenticationSuccess.html", model("test", "test"));

Yields:

Uncaught exception
java.lang.IllegalStateException: renderer.render(filePath, model) must not be null

Sorry, I must be missing something obvious.

[tipsy]

You're swallowing an exception and returning null. The render method is not allowed to return null. Do e.printStackTrace() instead, and you'll find out what the problem is.

[tipsy]

@Schachte here is a full example:

package io.javalin.examples;

import io.javalin.Javalin;
import io.javalin.rendering.JavalinRenderer;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Map;

public class HtmlExample {

    static {
        JavalinRenderer.register(HtmlExample::readFile, ".html");
    }

    public static void main(String[] args) {
        Javalin app = Javalin.create().start(7070);
        app.get("/my-path", ctx -> ctx.render("src/test/external/html.html"));
    }

    private static String readFile(String path, Map<String, Object> ignored) {
        try {
            return new String(Files.readAllBytes(Paths.get(path)));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

}

I'm guessing you specified a path which resulted in a IOException.

This still sounds like a strange thing to want to do though, could you tell me a bit about your use-case ?

[Schachte]

@tipsy Thanks for the example! I'll give it a shot. Essentially I'm doing an OAuth flow. The redirect URI from the OAuth provider hits my backend, which proxies a request to another third party. I want to conditionally return to the client some HTML from the server-side to let them know if the token authentication was successful. Because the redirect happens from an external source, this is the cleanest way I could think of to conditionally render HTML to the client to let them know if their auth was successful or not.

[tipsy]

If it's a one off thing it might be simpler to just set the result directly:

app.get("/", ctx -> ctx.html(new String(Files.readAllBytes(Paths.get("/path/to/file.html"))));

Note to self: This comes up a surprising amount of times, maybe I should add readFile to FileUtil 🤔

[Schachte]

ah, honestly, I like this solution better for my case. The handler itself does a ton of processing, but I just want to conditionally return the html of 2 different files conditionally. This looks exactly like what I needed. Currently I am calling ctx.html(MASSIVE_HTML_STRING_HERE) and it really clutters my class.

Thanks a lot for the help. I'll give this latter option a shot right now.

[tipsy]

You're welcome! It does sound like a better fit.

Very off topic, but I just visited your website and watched "Introduction To Docker and Docker Containers". Your style and the overall quality of the video is great! Would you be interested in creating a Javalin video?

[Schachte]

@tipsy Thanks! Actually sounds like a cool idea. I'll do that next!

[tipsy]

Great, happy to hear that! I've created an issue: https://github.com/tipsy/javalin/issues/549
I'll add some info there.