Example for a self-executable Spring Boot JAR, which accesses a DB driver (or any other 3rd-party JAR) from a external (non-bundled) directory.

This may be useful if you are not allowed to bundle the DB driver with your application.

Tips:

• Use ZIP as layout in spring-boot-maven-plugin (to generate the PropertiesLauncher entry in the MANIFEST.MF)
• Set <executable>true</executable> to prepend a shell script to the resulting JAR
• See command line examples for different types of running the JAR using the loader.path option

Expected result

Have a look for the output

Try to use external driver
-------------> Found driver h2 1.4

in all variants. The same application is started using different types of loading an external jar.

--------------------------
Variant A via java -jar
--------------------------
...
2019-04-25 22:51:59.934  INFO 26947 --- [           main] com.example.x.Application                : Started Application in 6.005 seconds (JVM running for 6.465)
Try to use external driver
-------------> Found driver h2 1.4

--------------------------
Variant B via java -jar
--------------------------
...
2019-04-25 22:52:06.447  INFO 26948 --- [           main] com.example.x.Application                : Started Application in 5.996 seconds (JVM running for 6.456)
Try to use external driver
-------------> Found driver h2 1.4

------------------------------------------------------------------------------------------------
Variant C via self-executable and loader.path-configuration from (default-) loader.properties
------------------------------------------------------------------------------------------------
...
Try to use external driver
-------------> Found driver h2 1.4

--------------------------------------------------------------------------------------------
Variant D via self-executable and loader.path-configuration from different property file 
--------------------------------------------------------------------------------------------
...
2019-04-25 22:52:19.494  INFO 26979 --- [           main] com.example.x.Application                : Started Application in 6.005 seconds (JVM running for 6.453)
Try to use external driver
-------------> Found driver h2 1.4

------------------------------------------------------------
Variant E via self-executable and LOADER_PATH environment
------------------------------------------------------------
...
2019-04-25 22:52:26.024  INFO 26995 --- [           main] com.example.x.Application                : Started Application in 5.967 seconds (JVM running for 6.439)
Try to use external driver
-------------> Found driver h2 1.4