How to add multiple application.properties files in spring-boot?

Spring Boot reads the property files in the following order. (From Spring Boot in Action)

1. Externally, in a /config subdirectory of the directory from which the application is run
2. Externally, in the directory from which the application is run
3. Internally, in a package named “config”
4. Internally, at the root of the classpath

The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).

So placing application.properties in a config sub-directory will give it a higher priority. In the following configuration, the application.properties from module_a will take precedence. You can add common defaults in application.properties and override them in individual modules by placing the configuration file in config/application.properties.

+common_module
  +src
    +main
      +java
      +resources/application.properties
+module_a
  +src
    +main
      +java
        +my/package/Application.java
      +resources/config/application.properties

What you are trying to do will not work when using Maven or Gradle. The reason is that when the artifact (jar most likely since you are using Spring Boot) is created, there will only be one application.properties file in the root.

I suggest you either change the name of the properties file on the support module and then configure Spring Boot to look for that file as well (take a look at this or this answer for pointers), or use some kind of merging task for your build tool (something like this perhaps)

The problem is exactly what @geoand describes. Spring boot loads top level application.properties and ignores any properties file with the exact name located in other jars.

But I didn't find any concrete implementation on how to fix this problem, so here it is for those who wants to know the implementation.

Consider this project configuration:

+main_module
  +src
    +main
      +java
        +my/package/Application.java
      +resources/application.properties
+module_aa
  +src
    +main
      +java
        +my/package/config/ModuleAAConfig.java
      +resources/module_aa.properties
+module_bb
  +src
    +main
      +java
        +my/package/config/ModuleBBConfig.java
      +resources/module_bb.properties

Now to load properties for each sub modules correctly we need to add @PropertySource annotation on the configs of each module i.e ModuleAAConfig.java, ModuleBBConfig.java.

Example:

ModuleAAConfig.java

package my.package.config;

@Configuration
@PropertySource(
    ignoreResourceNotFound = false,
    value = "classpath:module_aa.properties")
public class ModuleAAConfig {}

ModuleBBConfig.java

package my.package.config;

@Configuration
@PropertySource(
    ignoreResourceNotFound = false,
    value = "classpath:module_bb.properties")
public class ModuleBBConfig {}

---

Bonus:

If you want to load profile specific property, you can do so by utilizing spring variables e.g.

@PropertySource("classpath:module_aa-${spring.profiles.active}.properties")