JNDI und Service-Auflösung

package at.aydin.lab.jndi.legacy;

import javax.naming.*;

// Design Pattern: Service Locator
// Zweck: Versteckt JNDI-Lookups, behält aber die Laufzeitabhängigkeit von String-Namen.
public final class JndiServiceLocator {
    private final Context context;
    public JndiServiceLocator(Context context) {
        this.context = context;
    }

    public <T> T resolve(String name, Class<T> type) {
        try {
            return type.cast(context.lookup(name));
        } catch (NamingException ex) {
            throw new IllegalStateException(ex);
        }
    }
}

package at.aydin.lab.jndi.legacy;

import javax.naming.*;
import java.util.*;

public final class MemoryContext extends InitialContext {
    private static final Map<String, Object> VALUES = new HashMap<>();
    public MemoryContext() throws NamingException {
        super(true);
    }

    @Override
    public Object lookup(String name) throws NamingException {
        Object value = VALUES.get(name);
        if (value == null) throw new NameNotFoundException(name);
        return value;
    }

    @Override
    public void bind(String name, Object obj) throws NamingException {
        if (VALUES.putIfAbsent(name, obj) != null) throw new NameAlreadyBoundException(name);
    }

    @Override
    public void rebind(String name, Object obj) {
        VALUES.put(name, obj);
    }

    @Override
    public void close() {
    }
}

package at.aydin.lab.jndi.modern;

// Design Pattern: Port
// Zweck: Fachcode kennt keinen JNDI-Namen und keine NamingException.
public interface GreetingPort {
    String greet(String name);
}

package at.aydin.lab.jndi.legacy;

public interface GreetingPort {
    String greet(String name);
}

package at.aydin.lab.jndi.modern;

// Design Pattern: Port
// Zweck: Fachcode kennt keinen JNDI-Namen und keine NamingException.
public interface GreetingPort {
    String greet(String name);
}

package at.aydin.lab.jndi.legacy;

public final class GreetingService implements GreetingPort {
    @Override
    public String greet(String name) {
        return "Hallo " + name;
    }
}

package at.aydin.lab.jndi.modern;

import org.springframework.stereotype.Service;

@Service
public class GreetingService implements GreetingPort {
    public String greet(String name) {
        return "Hallo " + name;
    }
}

package at.aydin.lab.jndi.legacy;

// Design Pattern: Service Locator
// Zweck: Zeigt die versteckte Laufzeitabhängigkeit auf JNDI-Name und Naming-Infrastruktur.
public final class LegacyGreetingUseCase {
    private final JndiServiceLocator locator;
    public LegacyGreetingUseCase(JndiServiceLocator locator) {
        this.locator = locator;
    }

    public String execute(String name) {
        GreetingPort port = locator.resolve("service/greeting", GreetingPort.class);
        return port.greet(name);
    }
}

package at.aydin.lab.jndi.modern;

import org.springframework.stereotype.Component;

@Component
public class GreetingUseCase {
    private final GreetingPort port;
    public GreetingUseCase(GreetingPort port) {
        this.port = port;
    }

    public String execute(String name) {
        return port.greet(name);
    }
}