Running Spring Boot with PropertiesLauncher not picking up external jars

Please follow below and see if it works.

1. Build an executable jar that uses PropertiesLauncher

• In your pom.xml spring-boot-maven-plugin:
  • Set layout: ZIP or layout: JAR with mainClass=org.springframework.boot.loader.PropertiesLauncher (for Boot 2.x you can use layoutProperties).
  • Ensure the final jar contains org/springframework/boot/loader/PropertiesLauncher.

1. Run the jar, not the main class, from IntelliJ

• Create a Run/Debug Configuration of type Application (or JAR Application):
  • Main class: org.springframework.boot.loader.PropertiesLauncher
  • Use classpath of module: set to the module that contains your built jar only if you’re running from jar; otherwise prefer “JAR Application”.
  • Better: Use “Run/Debug Configuration | JAR Application”:
    • Path to JAR: <path-to-your-built-jar>.jar
    • Program arguments: your app args (if any)
    • VM options: -Dloader.path=/absolute/path/to/external-jars,/absolute/path/to/external-dir
    • Working directory: where relative loader.path would resolve from (recommend absolute paths)
    • Environment: LOADER_PATH can be set here instead of VM options if you prefer

Thanks, launching as JAR application worked.

Related - the classes I am instantiating that are being externally loaded are just being created with reflection (get the class name, instantiate an instance).

I would like to be able to make the class and associated code visible to the spring boot framework so I can use the spring boot annotations in the plugin. Is this possible?

Please try below options and see:

Component scan

•  Ensure jar is on classpath (loader.path).
•  @SpringBootApplication(scanBasePackages = {"app.pkg","plugin.pkg"}) or @ComponentScan("plugin.pkg").

Explicit import

• Plugin exposes @Configuration.
• Main app: @Import(PluginConfig.class) or an ImportSelector.

Auto-configuration (recommended for plugins)

• Plugin jar has @Configuration + conditions.
• Register:

1.               Boot 3: META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration
2.               Boot 2: META-INF/spring.factories (org.springframework.boot.autoconfigure.EnableAutoConfiguration=...)