Needle

Ultra-lightweight dependency injection for Java.
Minimal overhead, annotation-driven, zero config.

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Features

• Lightweight – tiny footprint, fast startup, no XML config
• Annotation-driven – @Component, @Wired, @Named, @PreDestroy
• Automatic resolution – scans classpath, resolves graphs, handles cycles
• Constructor & field injection – @Wired on fields or constructor params
• Method components – @Component on factory methods for programmatic wiring
• Shutdown hooks – automatic @PreDestroy cleanup via runtime hook

Getting Started

Install

Add dependency (Maven Central):

<dependency>
    <groupId>dev.pixelib.needle</groupId>
    <artifactId>needle</artifactId>
    <version>1.1.0</version>
</dependency>

Quick start

public class App {
    static void main(String[] args) {
        Needle needle = Needle.init(App.class);
    }
}

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More examples

Component classes

@Component
public class ExampleService {
    @Wired
    private Database db;
}

Named components

@Component
@Named("main")
public class MainDatabase implements Database { }

@Component
@Named("backup")
public class BackupDatabase implements Database { }

Factory / method components

@Component
public class AppConfig {
    @Component
    Database createDatabase() {
        return new Database("jdbc:...");
    }
}

Constructor injection

@Component
public class OrderService {
    private final PaymentGateway gateway;

    public OrderService(PaymentGateway gateway) {
        this.gateway = gateway;
    }
}

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Requirements

• Java 21+

Build

mvn clean test

JaCoCo coverage report generated at target/site/jacoco/index.html.

Contributing

PRs welcome. Keep it lightweight.

License

GNU General Public License v3.0 — see LICENSE.