What is the order of precedence when there are multiple Spring's environment profiles as set by spring.profiles.active

The order of the profiles in the spring.profiles.active system property doesn't matter. "Precedence" is defined by the declaration order of the beans, including beans specific to a profile, and the last bean definition wins.

Using your example, if -Dspring.profiles.active="default,dev" is used, the props bean in the default profile would be used here, simply because it's the last active definition of that bean:

<beans profile="dev">
    <bean id="props" class="org.springframework.context.support.PropertySourcesPlaceholderConfigurer">
        <property name="location" value="classpath:META-INF/dev.properties"/>
    </bean>
</beans>
<beans profile="default">
    <bean id="props" class="org.springframework.context.support.PropertySourcesPlaceholderConfigurer">
        <property name="location" value="classpath:META-INF/default.properties"/>
    </bean>
</beans>

Invert the order of the beans, and then the dev version would be used, regardless of how the profiles are ordered in spring.profiles.active.

Notice that I did not use <context:property-placeholder/> because it does not allow you to explicitly specify a bean id, and so I'm not sure what behavior it would exhibit if more than one is used. I imagine that the properties would be merged, so that properties defined by both would use the last definition, but properties specific to each file would remain intact.

Otherwise, in my experience, you would typically define beans in this order:

1. "Default" bean definitions, not specific to a profile
2. Overriding bean definitions in an environment-specific profile
3. Overriding bean definitions in a test-specific profile

This way, test profile beans would win if used in combination with other profiles; else you would either use environment-specific beans or default beans based on the profile.

superEB is right the order of the profiles doesn't matter for beans, the declaration order is more important there, but keep in mind that the order is important if you use profile based configuration files!

The last definition wins. I keep it in mind but:

It is very important to remember that if you have some default content of application.properties inside jar resources, then this resource content will overwrite entries from external content of less important profiles (other profiles defined earlier in spring.profiles.active).

Example profiles: spring.profiles.active=p1,p2,p3

Files in Jar resources: application-p1.properties and application-p3.properties

External files: application-p1.properties and application-p2.properties

Final order will be (last wins):

1. resource application.properties
2. external application.properties
3. resource application-p1.properties
4. external application-p1.properties
5. external application-p2.properties
6. resource application-p3.properties - HERE IS THE TRICK! this will overwrite properties defined in external files for p1 and p2 with values from resource version of p3
7. external application-p3.properties

So keep in mind that last wins but also that resource goes just before external