spring-boot-demo/configuration-properties/docs/08-diagnosing-a-value.md

← IDE metadata · Index

8. Diagnosing a value

Endpoint: BindingDiagnosticsEndpoint.

"The property is set but the application does not see it" is the most common configuration bug, and it is hard for one reason: a value carries no visible provenance. Spring Boot tracks it anyway — every property loaded from a file or a config tree carries an Origin naming the resource and the line.

$ curl -s 'localhost:8080/diag/origin?name=demo.mail.host'
{
  "property": "demo.mail.host",
  "effectiveValue": "smtp.example.com",
  "candidatesInPrecedenceOrder": [
    {
      "source": "OriginTrackedMapPropertySource {name='Config resource ... [application.yaml]'}",
      "value": "smtp.example.com",
      "origin": "class path resource [application.yaml] - 15:11"
    }
  ]
}

Line 15, column 11. Not "somewhere in your configuration".

How it works

for (ConfigurationPropertySource source : ConfigurationPropertySources.get(environment)) {
    ConfigurationProperty property =
            source.getConfigurationProperty(ConfigurationPropertyName.of(name));
    if (property != null) {
        // property.getValue(), property.getOrigin(), source.getUnderlyingSource()
    }
}

Iterating ConfigurationPropertySources.get(...) gives you the sources in precedence order. The first hit is the winner; everything after it exists and lost. A property with several holders is exactly what "my change had no effect" looks like from the inside — and the profiles project is entirely about that case.

Delete it before shipping

This endpoint prints whatever a mounted secret contains. If you want it permanently, put it behind the management port and authentication, or use Actuator's /actuator/env, which does the same job with sanitisation built in.

Without an endpoint

• --debug prints the auto-configuration report, not property origins.
• Setting logging.level.org.springframework.boot.context.config=TRACE logs which config data resources were loaded, in order — useful when the question is "was my file read at all".
• In a test, inject Environment and inspect getPropertySources() directly.