KZTG ServiceLoader.java

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.reflect.Constructor;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;

/**
 * Very simple replacement of {@link java.util.ServiceLoader} (from Java-6).
 *
 * @author Oifan
 *
 */
public class ServiceLoader {

    /**
     * Replacement of {@link java.util.ServiceLoader#load(Class)} method (from Java-6).
     * @param <S>
     * @param ifc
     * @return
     * @throws Exception
     */
    public static <S> Iterable<S> load(Class<S> ifc) {
        try {
            ClassLoader ldr = Thread.currentThread().getContextClassLoader();
            Enumeration<URL> e = ldr.getResources("META-INF/services/" + ifc.getName());
            Collection<S> services = new ArrayList<S>();
            while (e.hasMoreElements()) {
                URL url = e.nextElement();
                InputStream is = url.openStream();
                try {
                    BufferedReader r = new BufferedReader(new InputStreamReader(is, "UTF-8"));
                    while (true) {
                        String line = r.readLine();
                        if (line == null)
                            break;
                        int comment = line.indexOf('#');
                        if (comment >= 0)
                            line = line.substring(0, comment);
                        String name = line.trim();
                        if (name.length() == 0)
                            continue;
                        Class<?> clz = Class.forName(name, true, ldr);
                        Class<? extends S> impl = clz.asSubclass(ifc);
                        Constructor<? extends S> ctor = impl.getConstructor();
                        S svc = ctor.newInstance();
                        services.add(svc);
                    }
                } finally {
                    is.close();
                }
            }
            return services;
        } catch (RuntimeException e) {
            throw e;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

}