your-own-dependency-injection-framework

This is a small project that demonstrates how to build your own dependency injection framework.

It supports constructor and field injection.

The framework itself can be found under the "com.di.framework" package.
Sample applications are available under the tests.

How to use

1. Define how you want to map interfaces to their implementations.

public class DependencyInjectionConfig extends AbstractModule {
    
    @Override
    public void configure() {
        createMapping(GreetingService.class, WelcomeServiceImpl.class);
        createMapping(Logger.class, QuietLoggerImpl.class);
    }
}

2. Add @OwnInject annotation to the constructor or fields.

public class ConstructorInjectionClient {
    
    private final GreetingService service;
    private final Logger logger;
    
    @OwnInject
    public ConstructorInjectionClient(final GreetingService service, final Logger logger) {
        this.service = service;
        this.logger = logger;
    }
}

public class FieldInjectionClient {
    
    @OwnInject
    private GreetingService service;
    
    @OwnInject
    private Logger logger;

}

3. Use OwnDi to get your injected class.

public class SampleAppToTryDependencyInjection {
    
    public static void main(final String[] args) throws Exception {
        final OwnDiFramework ownDi = OwnDi.getFramework(new DependencyInjectionConfig());
        final ConstructorInjectionClient constructorInjectionClient = (ConstructorInjectionClient) ownDi.inject(ConstructorInjectionClient.class);
    }

}

How It Works

The two main classes are AbstractModule and OwnDiFramework.

AbstractModule contains interfaces with their implementations (subclasses).
OwnDiFramework performs the injection via Java reflection. It checks that the constructor or fields are annotated with the @OwnInject annotation.

Running Tests

To execute tests, use the Maven Wrapper included in the project. Run the following command from the root directory of the project:

./mvnw test

This command will compile the project with Java 21 and run all the tests using JUnit.

If you encounter any issues or have any questions, please refer to the documentation or reach out for support.