Master Spring Boot Externalized Config: Locations, Overrides & Advanced Options

1. Externalized Configuration

Spring Boot automatically searches for application.properties and application.yml in the following locations, ordered by priority (lower items override higher ones):

Classpath root

Classpath /config directory

Current working directory

Current directory /config directory

Direct sub‑directories of /config

Example file layout:

Root application.yml :

<code>pack:
  name: root name
  age: 66</code>

/config application.yml :

<code>pack:
  name: classpath /config name</code>

Injecting values:

<code>@Value("${pack.name}")
private String name;
@Value("${pack.age}")
private Integer age;</code>

Result:

<code>name = classpath /config name, age = 66</code>

Note: lower‑priority values (later in the list) override earlier ones, and the two files are merged rather than one replacing the other.

1.1 Change Default Configuration File Name

The default name is application . It can be changed with the spring.config.name property, e.g.:

<code>java -jar springboot-configfile-1.0.0.jar \
  --spring.config.name=pack</code>

1.2 Change Configuration File Location

Use spring.config.location to specify explicit locations (comma‑separated). The optional: prefix prevents startup failure if a file is missing.

<code>java -jar springboot-configfile-1.0.0.jar \
  --spring.config.location=optional:classpath:/pack.yml,optional:file:f:/</code>

When only a directory is given, Spring Boot appends the default file name automatically.

1.3 Additional Configuration Files

Use spring.config.additional-location to load extra files that can override values from the default locations.

<code>java -jar springboot-configfile-1.0.0.jar \
  --spring.config.location=optional:classpath:/pack.yml \
  --spring.config.name=pack \
  --spring.config.additional-location=optional:file:f:/pack-akf.yml</code>

Result shows the additional file overriding pack.name while preserving pack.age .

2. Detailed Configuration Options

2.1 Optional Locations

If a specified location does not exist, Spring Boot throws ConfigDataLocationNotFoundException . Prefixing the location with optional: makes the missing file harmless.

2.2 Wildcard Locations

Paths ending with * are treated as wildcards; all matching sub‑directories are scanned.

<code>java -jar springboot-configfile-1.0.0.jar \
  --spring.config.location=optional:classpath:/pack.yml \
  --spring.config.name=pack \
  --spring.config.additional-location=file:f:/sb-config/*/ \
  --spring.config.on-not-found=ignore</code>

Example code reads values from redis and mysql configuration files loaded via the wildcard.

2.3 Profile‑Specific Files

Spring Boot also loads application-{profile}.yml files. Later profiles override earlier ones.

<code>spring:
  profiles:
    active:
    - prod
    - live</code>

With pack-prod.yml and pack-live.yml , the live values replace the prod ones.

2.4 Importing Other Data

The spring.config.import property can import additional configuration files.

<code>pack:
  name: root name
  age: 66
---
spring:
  config:
    import:
      - file:f:/pack-akf.yml</code>

The imported file can override existing properties.

2.5 Importing Files Without Extension

Use bracket notation to tell Spring Boot the file’s format, e.g. file:f:/ack[.yml] imports a file without an extension as YAML.

<code>pack:
  email: [email protected]</code>

Injecting the value:

<code>@Value("${pack.email}")
private String email;</code>

Result: email = [email protected]

All the above techniques allow fine‑grained control over where and how Spring Boot loads configuration data.