Unable to use GSON to serialize anonymous class

Actual behavior (the bug) When attempting to configure Javalin to utilize Gson instead of Jackson for JSON serialization/deserialization, instead of having the configured JSON response body being generated, I receive the string null.

Expected behavior I would expect to see the configured JSON response.

To Reproduce Use the https://github.com/Jitsusama/javalin-gson-example repository as an example. Run the single test in the single class defined in that project and you’ll see what I mean.

Additional context My example project has DEBUG logging turned on by default in case it helps with diagnosis. Attached is an example log. The most pertinent entries from the log are as so:

Request method:	GET
Request URI:	http://localhost:8888
Proxy:			<none>
Request params:	<none>
Query params:	<none>
Form params:	<none>
Path params:	<none>
Headers:		Accept=*/*
Cookies:		<none>
Multiparts:		<none>
Body:			<none>

HTTP/1.1 500 Server Error
Date: Thu, 12 Jul 2018 11:52:17 GMT
Server: Javalin
Content-Type: application/x.my.custom.error+json
Content-Length: 4

null

[Jitsusama]

It’s possible I’m just stupid, but also, it might be possible that some other user could get bitten by this issue. Would you mind if I put through a PR to update the documentation example for Gson integration to call out this scenario?

[tipsy]

You’re welcome. If you really hate dependencies and need a simple mapOf method, you can use TemplateUtil.model():

Map<String, Object> myMap = model(
    "key1", value1,
    "key2", value2,
)