0.自定义注解

@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Downloader {

    String value();

}

1.声明采集器

public interface Collector {

    CollectResponse collect(CollectRequest request);

}

2.定义默认采集器,使用自定义注解修饰

@Downloader("default")
public class DefaultCollector implements Collector {

    @Override
    public CollectResponse collect(CollectRequest request) {
        return CollectResponse.create(request);
    }

}

3.定义工厂，管理Collector(核心用的扫描代码包+反射+注解值的对应关系)

public class CollectorFactory {

    protected Reflections reflections;

    private final Map<String, Collector> downloaders;

    public CollectorFactory() {
        this.reflections = new Reflections(
                ConfigurationBuilder.build("delta.fetch.collector", Thread.currentThread().getContextClassLoader())
                        .setMetadataAdapter(new CollectorJavaReflectionAdapter())
                        .setExpandSuperTypes(false));
        this.downloaders = new ConcurrentHashMap<>();
        loadDownloaderBean(reflections);
    }

    private void loadDownloaderBean(Reflections reflections) {
        Set<Class<?>> downloaderBeans = reflections.getTypesAnnotatedWith(Downloader.class);
        for (Class<?> downloaderBean : downloaderBeans) {
            addDownloaderBean(downloaderBean);
        }
    }

    private void addDownloaderBean(Class<?> spiderBeanClass) {
        Downloader downloader = spiderBeanClass.getAnnotation(Downloader.class);
        String name = downloader.value();
        try {
            downloaders.put(name.toLowerCase(Locale.ROOT), (Collector) spiderBeanClass.newInstance());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public Collector matchDownloader(CollectRequest request) {
        String serviceCode = request.getCollector();
        return downloaders.getOrDefault(serviceCode.toLowerCase(Locale.ROOT), new DefaultCollector());
    }
}

3.1 依赖

public class CollectorJavaReflectionAdapter extends JavaReflectionAdapter {

    @Override
    public Class<?> getOfCreateClassObject(Vfs.File file) throws Exception {
        return getOfCreateClassObject(file, Thread.currentThread().getContextClassLoader());
    }
}

4.基于注解+工厂的使用

private void processRequest(CollectRequest request) {
        Collector collector = collectorFactory.matchDownloader(request);
        // ......
    }