Here’s a code difference between Google Guice and PicoContainer to demonstrate their approach to Dependency Injection (DI).
1. Google Guice Example (Annotation-Based DI)
Steps:
- Define an interface and its implementation.
- Use
@Injectto specify dependencies. - Create a Guice module for binding.
- Use an injector to get an instance.
import com.google.inject.*;
// Step 1: Define an interface
interface Service {
void serve();
}
// Step 2: Implement the interface
class MyService implements Service {
public void serve() {
System.out.println("Service is running...");
}
}
// Step 3: Create a Guice module to bind the implementation
class MyModule extends AbstractModule {
@Override
protected void configure() {
bind(Service.class).to(MyService.class);
}
}
// Step 4: Inject the dependency using Guice
class Client {
private final Service service;
@Inject // Guice will automatically inject the dependency
public Client(Service service) {
this.service = service;
}
public void doSomething() {
service.serve();
}
}
// Step 5: Main method to run the code
public class GuiceExample {
public static void main(String[] args) {
Injector injector = Guice.createInjector(new MyModule());
Client client = injector.getInstance(Client.class);
client.doSomething();
}
}
Key Points in Guice:
- Uses annotations (
@Inject) for injection. - Uses a module (
AbstractModule) to define dependencies. - The injector (
Guice.createInjector(...)) resolves dependencies at runtime.
2. PicoContainer Example (Constructor-Based DI, No Annotations)
Steps:
- Define an interface and its implementation.
- Use constructor injection to inject dependencies.
- Register classes in PicoContainer and retrieve instances.
import org.picocontainer.*;
interface Service {
void serve();
}
class MyService implements Service {
public void serve() {
System.out.println("Service is running...");
}
}
class Client {
private final Service service;
// No annotations, constructor injection only
public Client(Service service) {
this.service = service;
}
public void doSomething() {
service.serve();
}
}
public class PicoExample {
public static void main(String[] args) {
MutablePicoContainer pico = new DefaultPicoContainer();
// Register dependencies
pico.addComponent(Service.class, MyService.class);
pico.addComponent(Client.class);
// Retrieve the Client instance with dependencies injected
Client client = pico.getComponent(Client.class);
client.doSomething();
}
}
Key Points in PicoContainer:
- Uses constructor injection only (no
@Injectannotation). - No separate binding module like Guice.
- Dependencies are registered manually using
pico.addComponent(...).
Code Difference Summary
| Feature | Google Guice | PicoContainer |
|---|---|---|
| Configuration | Uses modules (AbstractModule) |
Directly registers classes in the container |
| Injection Type | Supports constructor, field, and method injection | Constructor injection only |
| Annotations | Uses @Inject for DI |
No annotations required |
| Binding | Defined in a module using bind(...) |
Defined using pico.addComponent(...) |
| Dependency Resolution | Uses Injector.getInstance(Class.class) |
Uses pico.getComponent(Class.class) |
| Scalability | Suitable for large enterprise projects | Suitable for small lightweight projects |
Which One Should You Use?
- Use Google Guice if you prefer annotation-based DI, scalable dependency management, and AOP support.
- Use PicoContainer if you want a lightweight, constructor-based DI with minimal configuration.
Let me know if you need further clarification! 🚀
