Spring Boot extensionless config file: give the loader a properties hint

Name the format in the import

The test creates a file named relay-values with no suffix. It contains relay.batch-size=47 and relay.timeout=2s. application.properties imports that file URI with [.properties] appended. The child reports batch 47 and timeout 2000 milliseconds. This verifies parsing of one actual extensionless local file rather than a hand-built property map.

Some mounted files lack conventional extensions. An extension hint selects a loader without renaming the file supplied by the platform. The file remains a fixed URI; a relative import follows a different path rule.

Do not overstate the mount evidence

The file is written by the test in a temporary directory. No platform injects it and no secret value is present. The case does not check YAML, alternate encodings, permission errors or rotation. A configtree is another option when each file represents one key.

A successful parse is only the first step. Keep typed validation for ranges, endpoint shape and cross-setting constraints.

Checked source

spring.config.import=file:/absolute/path/relay-values[.properties]
# relay-values has no extension and contains relay.batch-size=47

Verification boundary

RelaySettingsProcessTest.extensionlessPropertiesFileNeedsAnExtensionHint. The full fixture is in the downloadable source kit.

Common Mistakes

• Do not expect the loader to infer every extensionless file format.
• Do not confuse a fixed file URI with a relative import.
• Do not call a temporary-file test a production platform mount test.

Read next

Spring Boot configtree: bind one file per property in a child JVM, Spring Boot nested config imports: each file becomes the next base directory, Spring Boot external config file: bind the value the process actually loads, Spring Boot file-tree tests: prove binding without claiming secret delivery.