Is it possible to load Spring-Boot properties from config folder within parent module of a Maven multi-module project?

Question

Is it possible to load multiple Spring-Boot .yml config files from a config folder within parent module of a multi-module project?

So, structure looks like this:

parent-module/
  pom.xml
  config/
    application-prd.yml
    application-dev.yml
  module1
    pom.xml
    src/main/resources/
      logback-spring.xml
      bootstrap.yml

Is this possible? How can it be done?

So, if I execute from root folder of multi-module project, I would use this command:

mvn -pl module1 spring-boot:run
   OR
mvn spring-boot:run

And I would hope that the config folder would be included in the classpath? I am trying to do this but not getting it to work. Am I missing something?

We know this to be true: Child POMs inherit properties, dependencies, and plugin configurations from the parent. But shouldn't that mean that {parent}/config/application.yml is in the classpath already?

Example project to use for proving: https://github.com/djangofan/spring-boot-maven-multi-module-example . Clone it and modify if you think you can solve it.

Answer 1

Yes, it is possible.

Maven changes the working directory to the module's directory when you use the -pl. So it is no longer the root which has the config/ dir.

Either you can refactor your maven multi-module setup to a way that you can package the common application.yml files and than use them. I wouldn't recommend that as it has many pitfalls.

Probably easier to use the --spring.config-location

$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties

I can not test it at the moment but if it doesn't work you can always try the -Dspring.config.location or the SPRING_CONFIG_LOCATION environment variable.

Answer 2

I found a customized way of doing it, which I still consider to be a hack, as you can see below, but I am still looking for an actual answer to my question, if it exists.

@Slf4j
@SpringBootApplication
public class Application {

    private static String DEV_PROPS = "application-dev.properties";
    private static String PRD_PROPS = "application-prd.properties";
    private static String DEFAULT_PROPS = "application.properties";

    private static Path CONFIG = Paths.get(System.getProperty("user.dir"))
            .resolve(Paths.get(".."))
            .resolve("config");

    private static final String EXT_CONFIG_DIR = CONFIG.toString() + File.separator;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
        PropertySourcesPlaceholderConfigurer properties = new PropertySourcesPlaceholderConfigurer();
        Resource[] resources = new Resource[] {
                        new FileSystemResource(EXT_CONFIG_DIR + PRD_PROPS),
                        new FileSystemResource(EXT_CONFIG_DIR + DEV_PROPS),
                        new ClassPathResource(DEFAULT_PROPS)
                };
        log.info("Properties: " + Arrays.deepToString(resources));
        properties.setIgnoreResourceNotFound(true);
        properties.setLocations(resources);
        return properties;
    }

}

The problem with this method, is that configuration has to be changed to support additional environment profile names.

Answer 3

No need to write code. You can use Exec Maven Plugin for this. Add the plugin to the parent module:

<build>
  <plugins>
    <plugin>
      <groupId>org.codehaus.mojo</groupId>
      <artifactId>exec-maven-plugin</artifactId>
      <version>1.6.0</version>
      <configuration>
        <mainClass>PACKAGE.MODULE_MAIN_CLASS</mainClass>
        <arguments>
          <argument>--spring.profiles.active=dev</argument>
        </arguments>
      </configuration>
    </plugin>
  </plugins>
</build>

then run mvn install once and then mvn exec whenever you want to start the application.

mvn exec:java -pl module1

For more on Maven goals in a multi-module project, check this answer https://stackoverflow.com/a/11091569/512667 .

Another way to configure this is like so, which requires the workingDirectory arg:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <mainClass>com.example.Application</mainClass>
        <workingDirectory>${maven.multiModuleProjectDirectory}</workingDirectory>
        <arguments>
            <argument>--spring.profiles.active=dev</argument>
        </arguments>
    </configuration>
</plugin>

In this case, execute:

mvn spring-boot:run -pl module1