Spring Boot - Dynamic Loading Jar Example

This project demonstrates how you can use SpringBoot to dynamically at run-time load in different implementation of an interface at run-time and have the application detect them. This project mostly matches this structure:

NOTE: Demo now updated with some Kotlin Classes

QuickStart

# Compile and run with gradle wrapper
git clone https://github.com/jeeftor/SpringBoot-Dynamic-JarLoad.git
cd SpringBoot-Dynamic-JarLoad
./run.sh

Overview

commons
app
defaultSystemAdapter
foodAdapters

The first library is commons which defines the SystemAdapter protocol and an enum of SystemAdapter type. Any implementation that we will load in later (defaultSystemAdapter, and foodAdapters) will need to reference this library in order to implement the protocol.

Our Application app is the main application and it includes a single NullSystemAdapater which is a default stand-in system adapter so it will compile.

the run.sh will build all 4 jar files.

It will then run the system three times:

• Without Any Adapters
• With the DefaultAdapters
• With the food Adapters

The SystemAdapterFactory will detect the loaded adapters and print out some basic info:

@Service
public class SystemAdapterFactory {

    @Autowired
    List<SystemAdapter> adapters;


    @PostConstruct
    void listAdapters() {
        System.out.println("\n\n-------SYSTEM ADAPTERS ------\n");
        for (SystemAdapter adapter: adapters) {
            System.out.println("...Loaded Class: " + adapter.getClass() + " of type: " + adapter.getType().toString());
        }
        System.out.println("\n-------------------------------");
    }

}

So when we run it looks like this:

Running the app as-is

java -jar -jar app/build/libs/app-0.0.1-SNAPSHOT.jar

-------SYSTEM ADAPTERS ------

...Loaded Class: class org.company.adapters.NullAdapter of type: NULL

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Running with the first jar:

java -Dloader.path=file:./defaultImplementation/build/libs/defaultImplementation-0.0.1-SNAPSHOT.jar -Dloader.debug=false -jar app/build/libs/app-0.0.1-SNAPSHOT.jar

-------SYSTEM ADAPTERS ------

...Loaded Class: class org.company.adapters.DefaultTurkeyAdapter of type: Turkey ...Loaded Class: class org.company.adapters.DefaultModemAdapter of type: Modem ...Loaded Class: class org.company.adapters.NullAdapter of type: NULL

---

And the second

java -Dloader.path=file:./foodAdapters/build/libs/foodAdapters-0.0.1-SNAPSHOT.jar -Dloader.debug=false -jar app/build/libs/app-0.0.1-SNAPSHOT.jar

-------SYSTEM ADAPTERS ------

...Loaded Class: class org.company.adapters.ThanksgivingAdapter of type: Turkey ...Loaded Class: class org.company.adapters.TacoTruckAdapter of type: Taco ...Loaded Class: class org.company.adapters.NullAdapter of type: NULL

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