Service Registry und ServiceLoader

<?xml version="1.0" encoding="UTF-8"?>
        <project xmlns="http://maven.apache.org/POM/4.0.0"
                 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
            <modelVersion>4.0.0</modelVersion>
            <parent>
                <groupId>at.aydin.academy</groupId>
                <artifactId>29osgiserviceregistry-pair</artifactId>
                <version>1.0.0</version>
                <relativePath>../pom.xml</relativePath>
            </parent>
            <artifactId>osgi-registry-legacy</artifactId>
            <packaging>jar</packaging>
            <name>OSGi Registry Legacy</name>

            <dependencies>

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <scope>test</scope>
</dependency>

            </dependencies>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-compiler-plugin</artifactId>
                    </plugin>

                </plugins>
            </build>
        </project>

package at.aydin.lab.osgi.legacy;

public interface PaymentService {
    String pay(int cents);
}

package at.aydin.lab.osgi.legacy;

import java.util.*;

// Design Pattern: Service Registry
// Zweck: Dienste können dynamisch registriert, ersetzt und entfernt werden.
public final class ServiceRegistry {
    private final Map<Class<?>, Object> services = new HashMap<>();
    public <T> void register(Class<T> type, T service) {
        services.put(type, service);
    }

    public void unregister(Class<?> type) {
        services.remove(type);
    }

    public <T> Optional<T> find(Class<T> type) {
        return Optional.ofNullable(type.cast(services.get(type)));
    }
}

package at.aydin.lab.osgi.legacy;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class ServiceRegistryTest {
    @Test
    void supportsLifecycle() {
        var r = new ServiceRegistry();
        r.register(PaymentService.class, c -> "PAID " + c);
        assertEquals("PAID 100", r.find(PaymentService.class).orElseThrow().pay(100));
        r.unregister(PaymentService.class);
        assertTrue(r.find(PaymentService.class).isEmpty());
    }
}