Propertysources precedence when merging the property source from @ConfigurationProperties' locations

[ilayaperumalg]

When the merge attribute for @ConfigurationProperties is set to true to merge the environment property sources along with the property sources specified in the locations, the property sources from the locations attribute gets the highest precedence.

Is this precedence level set for a reason? I was expecting the property source from locations getting the lowest precedence.

For instance, if I have a commandLine args for the application, wouldn't I expect this args override all the other property source including the one specified in locations attribute of ConfigurationProperties annotation.

[wilkinsona]

@ilayaperumalg Originally, the location attribute ignored the rest of the environment completely. The merge attribute was added as that surprised people. They wanted their custom location to override the environment. You want it to be overridden by the environment. Satisfying both camps will, IMO, make things too complex. We're actually considering getting rid of locations altogether (see #5129). Please comment on that issue if you feel strongly that it should be retained and have a compelling use case for the added complexity.

[ilayaperumalg]

@wilkinsona I see. I agree that it makes sense to keep one way of support and less complexity. Would be nice if we add Javadoc that says the precedence order on merge.

Thanks!

[wilkinsona]

As it happens, @snicoll improved the javadoc yesterday. See 594c891

[ilayaperumalg]

Cool! 👍