JayWire Dependency Injection

A very small and lightweight dependency injection framework for Java 8 without magic. Main features are:

• 100% pure Java code (no XML, no config files)
• Explicit, compile-time wireing
• Typesafe
• Modular and extendable
• Small and easy

JayWire avoids any magic, that means:

• No classpath scanning
• No reflection
• No annotations
• No bytecode enhancement / weaving
• No transparent proxies
• No code generation
• No hidden / static state

Getting the library

Add this dependency to your Maven build:

<dependency>
   <groupId>com.vanillasource.jaywire</groupId>
   <artifactId>jaywire</artifactId>
   <version>1.1.0</version>
</dependency>

This will include the basic interfaces and scopes for standalone usage. For integration with Web-frameworks see Wiki.

Wireing everything together

For a simple application a single "Module" object wireing everything together is written this way:

import com.vanillasource.jaywire.standalone.StandaloneModule;

public class MyAppModule extends StandaloneModule {
   public Database getDatabase() {
      return singleton(() -> new MyAppDatabase(...));
   }

   public ServiceA getServiceA() {
      return singleton(() -> new ServiceA(getDatabase()));
   }

   public ServiceB getServiceB() {
      return singleton(() -> new ServiceB(getDatabase(), getServiceA());
   }
}

In this example there is a Database, ServiceA and ServiceB, all of them singletons. It is assumed that these services / classes are written in the usual Object-Oriented approach by taking all required dependencies as constructor parameters. These dependencies are then "injected" by simply calling the appropriate methods to get fully constructed dependencies and supplying them as parameters to objects.

You can use the MyAppModule then at the "top" of your application to start processing:

public class MyApp {
   public static final void main(String[] argv) {
      MyAppModule module = new MyAppModule();
      module.getServiceB().run();
   }
}

Documentation

The JayWire API Documentation.

Please visit the JayWire Wiki for more information.

Related external projects

• Pouch is an interesting rethinking of the Service Locator pattern.