No Converter registered for interface java.util.Map

[ecmrauh]

Describe the bug
I don't know if it is a bug or a missing feature (or just my fault). I try to use a Map<String, String> as configuration value. I created a custom converter as described here. The example with the int works, using a Map fails.

Expected behavior
It should possible to use a Map as configuration value.

Actual behavior
An exception is thrown (java.lang.IllegalArgumentException: No Converter registered for interface java.util.Map).

But the converter is present and it is used with e.g. ints and doubles.

To Reproduce
Steps to reproduce the behavior:

1. Setup a minimal example like this one and change int to Map<String, String>.
2. Inject the config and try to use the value.

Configuration

My final goal is to use something like:

config.global.setting = value
config.tenant-map.param1 = xxx
config.tenant-map.param1 = yyy

Environment (please complete the following information):

• Output of uname -a:
  Linux debian 5.4.0-0.bpo.3-amd64 Switch to the Maven distributed copy of the SubstrateVM annotations #1 SMP Debian 5.4.13-1~bpo10+1 (2020-02-07) x86_64 GNU/Linux

• Output of java -version:
  openjdk version "11.0.6" 2020-01-14
  OpenJDK Runtime Environment (build 11.0.6+10-post-Debian-1deb10u1)
  OpenJDK 64-Bit Server VM (build 11.0.6+10-post-Debian-1deb10u1, mixed mode, sharing)

• Quarkus version: 1.2.1-Final and 1.3.0-Final

• Build tool (mvn --version):
  Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
  Java version: 11.0.6, vendor: Debian, runtime: /usr/lib/jvm/java-11-openjdk-amd64
  Default locale: de_DE, platform encoding: UTF-8
  OS name: "linux", version: "5.4.0-0.bpo.3-amd64", arch: "amd64", family: "unix"

Additional context

The example descriped here works, but changing Double to Map<String, String> fails.

This issue might be similar to #7856.

[geoand]

I think this behavior is by design, but I am not 100% sure, so let's ask the expert @dmlloyd

[dmlloyd]

You're essentially hitting two different problems here. One is that MicroProfile Config does not support generic converter types; Map is a generic type, having two type parameters. The other is that converters only apply to single string values - they cannot be used to aggregate values from multiple properties without special support from the runtime.

[geoand]

I'm going to close this as invalid. Feel free to reopen if you feel it's not been adequately covered

[ecmrauh]

Thanks for your quick response! I wasn't aware of that. After reading issues like e.g. this one, I thought it would be possible somehow. If not, I will have to live with that... 😕

[dmlloyd]

We have special support for it within our Quarkus configuration code, which is separate from the standard CDI-based stuff. Really I think the MP Config spec needs a bit of a rethink in this area though. My first step in this direction is eclipse/microprofile-config#545.

[ecmrauh]

Thanks for the clarification and your efforts!!