Configuring Spring Framework with YAML

Spring application can be configured using YAML as effectively as using properties file. With YAML file one can,

• Create environment specific profiles

• Define properties at application level

• Define (or override) properties at profile level

Spring Framework loads application.yml by default just the way it loads application.properties. If you want to change the name of the yml file you'll have to use context loader to tell what file to look for.

Must knows of the yml based configuration

1. Profiles - YML supports multiple profiles in a single file. One can define environment specific configurations as profiles in a single file.
2. Profiles separator - YML configuration file uses 3 dashes (---) to separate a profile. Every property you define after --- is specific to that profile.
3. Profile name - Give profile a name using spring.config.activate.on-profile property.
4. Active profile(s) - Define which profile or profiles are active using spring.profiles.active property. More than one profile can be active using comma separated profile names.
5. Property overriding - If a property is defined more than once in a file, the last occurrence of the property is used. If same property is defined in multiple "active" profiles, last occurrence of the property is used.

E.g.  

In this configuration file,

• 2 profiles are defined, mongo and marklogic
• document-writer, batch-size, number-of-documents and document-format properties are common to both profiles
• database property is defined differently for each profile
• host property is available only to marklogic profile. Attempting to use host property when marklogic profile is not active will result in an error.