Avoid escaping line breaks in a custom attribute using Thymeleaf

Question

I process SVG templates using Thymeleaf and encountered a problem replacing base64-encoded embedded images.

So, the source tag looks like this:

Each line of base64-encoded image data consists of 76 characters and a line break (LF), and I want to keep this structure, because some SVG renderers break when a file contains very long lines.

The problem is, when I set the imageBase64 context variable to a base64 string with line breaks, Thymeleaf escapes LF characters as and, obviously, this breaks base64 decoders.

I know, there is th:utext attribute that works for tag inner text, but is there a way to avoid contents escaping while using a custom attribute?

Reproducer

https://github.com/d-bykov/thymeleaf-escaping-reproducer

Running this project will generate this SVG file, which contains Base64-encoded image with tokens instead of line break characters.

GitHub renders it just fine, but some other applications don't.

andrewJames · Accepted Answer

In Summary

XML handlers will escape newlines to as you have seen. But that is not something which HTML requires, so try using the HTML template mode instead.

My Test

In your Kotlin you are setting the template mode to XML:

templateResolver.templateMode = TemplateMode.XML

Instead, use HTML

templateResolver.templateMode = TemplateMode.HTML

In my Java version of your code, I actually used this:

templateResolver.setTemplateMode(TemplateMode.HTML);

The end result, when I used my own PNG, was the following content:

(I added a newline at the start of the base64 string, also, just to get the entire string content aligned to the left in the file - you probably don't need or want to do that).

Avoid escaping line breaks in a custom attribute using Thymeleaf

Reproducer

Answers (1)

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