BootstrapApplicationListener overrides custom environment

[samjoseph]

The BootstrapApplicationListener defines its own environment when it creates the Spring Application using the Spring Builder. This overrides the custom environment we have provided for our application during the initial application run invocation.

We specify a custom environment class for our application for reasons specified in this issue

The BootstrapApplicationListener should provide a way for applications to specify their own environment class instead of defining its bootstrapEnvironment using new StandardEnvironment().

private ConfigurableApplicationContext bootstrapServiceContext( ConfigurableEnvironment environment, final SpringApplication application, String configName) { **StandardEnvironment bootstrapEnvironment = new StandardEnvironment();** MutablePropertySources bootstrapProperties = bootstrapEnvironment .getPropertySources(); for (PropertySource<?> source : bootstrapProperties) { bootstrapProperties.remove(source.getName()); }

[spencergibb]

I'm a bit unsure how we would go about doing that. It's too early in the lifecycle to have a bean. The only other thought would be to extract env creation to a protected method and then you'd need to setup your own entry in spring.factories in org.springframework.context.ApplicationListener and disable the provided one. @dsyer thoughts?

[dsyer]

I can't think of a reason you'd want to override the environment implementation. Maybe we need to dig into the reason for asking in the first place, in case there's a better solution.

[spencergibb]

Alright, we'll wait for the OP

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[samjoseph]

@dsyer

This is the reason why we have a overridden environment implementation

Consider following property
sam.credential.property=MockCredentialVault("Test")

Where MockCredentialVault is a type of Credential Vault System we want to access with the "Test" value

So we need to have access to all property sources since the MockCredentialVault("Test") could also be in a different file

application.properties
sam.credential.property=${vault.system.placeholder}

prod.properties
vault.system.placeholder=MockCredentialVault("Test")

We felt that the a custom environment would be a better place to do this resolution as it has access to all property sources and in the case of custom environment we also have a central location to cache & refresh the retrieved credentials.

[spencergibb]

That is very unusual and so far no one else has requested it. Let's see if there is more interest.

[dsyer]

I'm also still a bit unclear about why this can't be achieved with an EnvironmentPostProcessor. There are some lifecycle issues with EPPs that we are vaguely aware of (some implementations don't like to be run twice), but without a concrete code sample it's hard to say if this is one of those. Can you create a sample app (maybe one that doesn't actually use Vault, so it is easy to tinker with)?