Configuration migration: spring.config.import, structured config trees.

Boot 2.4 reworked config loading and Boot 3 carries it forward: spring.config.import is now the explicit, ordered way to pull in extra config — including config trees, Vault, and Consul — replacing the old implicit bootstrap.yml and ad-hoc property sources. It makes "where does this property come from" deterministic.

spring.config.import

You declare additional config sources directly, and they're imported in order, after the file that declares them:

spring:
  config:
    import:
      - optional:file:./local.yml          # optional: don't fail if missing
      - configtree:/etc/config/            # a directory tree of values
      - vault://secret/myapp                # Spring Cloud Vault
      - consul:                             # Spring Cloud Consul

The optional: prefix means a missing source is skipped rather than failing startup. Crucially, this replaced the old bootstrap context: Spring Cloud config servers, Vault, and Consul used to load via a separate bootstrap.yml phase; now they're ordinary imports in application.yml, so there's one loading model instead of two.

Config trees

A config tree maps a directory to properties: each file's name is the key and its contents are the value. This is exactly how Kubernetes and Docker mount secrets and config maps — as files:

/etc/config/
├── spring.datasource.username   -> file contents "appuser"
└── spring.datasource.password   -> file contents "s3cr3t"

spring.config.import: "configtree:/etc/config/"

Now spring.datasource.password resolves from the mounted file — no env-var indirection, and secrets never sit in application.yml.

Other migration notes

• Profile-specific docs in a single file use --- separators with spring.config.activate.on-profile (the old spring.profiles key was removed).
• Profile-specific files cannot themselves declare spring.profiles.active/group — that's only valid in the main document.