YAML documents ordering is not respected

[snicoll]

Ordering in YAML documents is broken since a Properties object doesn't retain ordering.

See https://jira.spring.io/browse/SPR-12471

[snicoll]

I tried a couple of options but did not find a way to implement that easily. The current algorithm either returns a flat view unordered or a Map that keeps the ordering but boot expects a flat view.

@dsyer thoughts?

[dsyer]

I guess anyone who relies on the flattened view has to accept that it's unordered (i.e. they have to know that Properties are unordered). We could provide an alternative flat view using a Map?

[snicoll]

What about that candidate fix then? apache/grails-core@d9670e1

[dsyer]

I'm not sure what problem that is solving. The flat view is still Properties right? If all we need to do to keep everyone happy is to make the non-flat view ordered, then it's easy (and doesn't require changes in Boot).

[snicoll]

@graemerocher ping?

[graemerocher]

I'm not sure what input you need from me here. It is quite common in YAML configuration to use order since YAML has constructs for ordering (lists etc.). If these are lost they break the YAML definition which comes into play when you use http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/env/EnumerablePropertySource.html

To enumerate the keys. The fix is fairly simple in that using YamlMapFactoryBean fixes the problem.

[philwebb]

We can't directly use YamlMapFactoryBean since it doesn't flatten out the map keys. I've made a change to YamlProcessor SPR-12499 so that we can extend that directly.

[snicoll]

It looks like this broke other use cases. XD has multiple YAML documents and it seems that instead of merging these, they got overridden.

Something like

---

# Redis properties
spring:
  redis:
   port: 6379
   host: localhost
   pool.maxIdle: 8
   pool.minIdle: 0
   pool.maxActive: 8
   pool.maxWait: -1

---
# RabbitMQ properties
spring:
  rabbitmq:
   addresses: localhost:5672
   username: guest
   password: guest
   virtual_host: /
   useSSL: false
   sslProperties:

---
# Hadoop properties
spring:
  hadoop:
   fsUri: hdfs://localhost:8020