在Spring Boot应用程序中添加条件外部PropertySource

Question

I'm currently using an EnvironmentPostProcessor to add my external PropertySource, the code looks like this :

public class ExternalPropertySourceEnvironmentPostProcessor implements EnvironmentPostProcessor
{
    private static final String EXTERNAL_PROPERTY_SOURCE_NAME = "ExternalPropertySource";

    @Override
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application)
    {
        if (environment.acceptsProfiles(Profiles.EXTERNAL_PROPERTY_SOURCE_ENABLED_PROFILE)) {
            environment.getPropertySources()
                       .addLast(new ExternalPropertySource(EXTERNAL_PROPERTY_SOURCE_NAME, new ExternalSource()));
        }
    }
}

A spring.factories is also used to register this EnvironmentPostProcessor.

This code actually works if the profile is set in the vm environment variables, but if it is added in src/main/resources/application.yml, the profile doesn't seem to be injected yet in the environment and is not returned by the environment.getActiveProfiles(). I've tried using the interface Ordered with the lowest precedence, but it doesn't help.

To add a bit of context around what I'm trying to achieve, this class is in a small library that adds an external property source like a database. Then we can use it in some other spring boot applications. Something like Spring Cloud Config does.

I'd like a clean way to enable or disable this property source depending on the environment where the code runs. I don't mind using something else then profiles or even another way to inject the property source, I just want something clean that doesn't depend on several factors to work.

The main problem in my code right now is that I'm using spring boot's property sources to make my own property source configurable.

UPDATE : I used a Spring Cloud app to debug this, and was confusing the bootstrap context with the normal spring boot context. See my answer below.

Answer 1

Further investigation made me figure out the problem appeared only with a Spring Cloud application.

In fact the breakpoint I had in this code was triggered twice, once after the bootstrap context initialization and once after the spring boot context initialization. I was only debugging the profiles in the first occurence. At that point, only the bootstrap.yml properties are loaded and not the ones from the application.yml file. The second occurence obviously had the profiles from my application.yml file.

My code worked as expected with a vanilla Spring Boot application. As the documentation states :

The Environment has already been prepared with all the usual property sources that Spring Boot loads by default.

I was confused by the behaviour of my app which seemed to be different from that statement, but it was Spring Cloud's bootstrap that was messing with my debugging.

Since I need a PropertySource that has the highest precedence, I need to add it in the post bootstrap initialization for Spring Cloud apps. I used an init flag on my EnvironmentPostProcessor so it doesn't get executed twice and used the bootstrap.yml on Spring Cloud apps to set the profile.

TL;DR : With Spring Cloud, an EnvironmentPostProcessor gets called twice: once after the bootstrap init and once after the normal Spring Boot context init. If you need injected properties and are targeting the Spring Cloud's post bootstrap initialization, use the bootstrap.yml instead of application.yml.