How do you manage property files in a Mule application?

• A. Use environment variables only
• B. Use mule-app.properties for environment-specific values; reference with p('name') in MEL or #[...] in flows.
• C. Hard-code values
• D. Property files are deprecated in Mule 4.

Answer: (B)

Externalizing configuration so a single application can run in multiple environments is what this question tests. In Mule, you store environment-specific values in a property file on the app’s classpath, typically mule-app.properties. You then read those values at runtime using the property placeholder function p('name')—in MEL or in Flow expressions with #[p('name')]. For example, a URL defined as db.url in the properties file can be retrieved as #[p('db.url')] wherever you need it. This pattern lets you swap values per environment (dev, test, prod) without changing the application code, by providing a different properties file or overriding properties during deployment. Property files are supported in Mule 4 and remain the standard way to manage configuration rather than hard-coding values or relying solely on environment variables.