How to use Thymeleaf to process YAML files?

Question

I'm trying to process YAML files using Thymeleaf. A sample file is given below:

apiVersion: v1
kind: Service
metadata:
  name: [[${app['name']}]]
  labels:
    app: [[${app['name']}]]
spec:
  type: NodePort
  ports:
  - port: 80
    protocol: TCP
    name: http
  - port: 443
    protocol: TCP
    name: https
  selector:
    app: nginx

The value app.name comes from another YAML file that I parse at runtime.

What I've tried so far:

1. Creating a MessageSource with Properties

   TemplateEngine templateEngine = new TemplateEngine();
   templateEngine.setTemplateResolver(templateResolver);
   StandardMessageResolver messageResolver = new StandardMessageResolver();
   messageResolver.setDefaultMessages(props); // contains app.name
   templateEngine.setMessageResolver(messageResolver);
   

2. Setting a variable in the context

   map.put("app.name", "test");
   context.setVariables(map); // contains app.name
   

But I keep getting the error:

Exception evaluating OGNL expression: "app['name']
...
Caused by: ognl.OgnlException: source is null for getProperty(null, "name")

Using Thymeleaf 3.0.3.RELEASE. I'm using Spring and not using Spring, in the sense that the spring-boot-starter-thymeleaf brings in so much baggage mostly needed for HTML, I decided to just instantiate the template resolver and engine myself. It seems like people rarely process TEXT using Thymeleaf; all the examples I came across are HTML.

I'd also like to know how to include a fragment of YAML in my templates.

Edit: Thanks to @Metroids, I got it working. Here's the link to my sample app in case someone else has a similar problem.

Answer 1

I think there is some confusion about how to access properties here... if you want to use the expression ${app['name']} in your template, your context should look like this:

Map<String, Object> app = new HashMap<>();
app.put("name", "test");

Context context = new Context();
context.setVariable("app", app);
engine.process("template", context);

Using map.put("app.name", "test"); is not a good idea because a syntax of something.something has a meaning in expression language (calling a getter/setter on an object).

Edit: Including a text template would look something like this:

a.txt

blah blah blah 
[# th:insert="b"/] 
blah blah blah 

b.txt

Text in b.txt
that should be included

Edit 2: If you want to use messages, rather than a context this should work:

apiVersion: v1
kind: Service
metadata:
  name: [[#{app.name}]]
  labels:
    app: [[#{app.name}]]