JSON keys containing a dot from CF environment are not handled as a single path segment

[schulzh]

This PR changes the handling of JSON keys in the CloudFoundry VCAP_SERVICES environment variable so that they represent only a single path segment at a time.

Before this change, if the JSON contained an object key with dots, the key would be treated as individual path segments, instead of a single one.
E.g. the VCAP_SERVICES variable

{
  "user-provided": [
    {
      "name": "test",
      "label": "test-label",
      "credentials": {
        "key.with.dots": {
          "username": "foo",
          "password": "bar"
        }
      }
    }
  ]
}

Would lead to the spring property:
vcap.services.test.credentials.key.with.dots.username=foo
Instead of the escaped version:
vcap.services.test.credentials[key.with.dots].username=foo

This causes problems e.g. when trying to bind these properties to a map, as it would not be filled with any values:

@ConfigurationProperties("vcap.services.test")
public class CfEnvCredentials {
    public final Map<String, BasicAuthentication> credentials;
    [...]
}

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[philwebb]

@schulzh What sort of generic types do you have on your Map? We should automatically deal with this for String and scalar types (see this test). Do you have a small sample that show the problem that lead to you creating this PR?

[schulzh]

I have a Map<String, BasicAuthentication>, with this BasicAuthentication class:

public class BasicAuthentication extends Authentication {
    public final String username;
    public final String password;
}

This is meant to supply Authentication information for arbitrary hosts, which will be the keys of the map, therefore the dots in the keys.

I just tested a Map<String, String> example and indeed, it worked. Sorry, I should have tested the actual example before. I'll edit the PR with the actual example.

[mbhave]

I think we'd have to do this for any characters that are not alpha-numeric or -.

[snicoll]

@schulzh would you have time to revisit the PR based on Madura's feedback?

[mbhave]

@schulzh Thank you for making your first contribution to Spring Boot. This has now been merged along with this addition.

[wilkinsona]

Unfortunately, this change caused some unanticipated problems and we're going to have to revert it. Please see #20343 for details. We've opened #20400 to take another look at the problem. It's tentatively scheduled for 2.3.