✔ Services dynamisch laden

package de.tutorials.appserver;

import java.io.File;
import java.io.FilenameFilter;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ServiceLoader;

public class Server {

  String defaultPluginsLocation = "c:/temp/projects/plugins/";
  String pluginsLocation = System.getProperty("de.tutorials.pluginsLocation", defaultPluginsLocation);


  public static void main(String[] args) throws Exception {
    new Server().boot();
  }


  private void boot() throws Exception {
    registerPlugins();
    run();
  }


  private void run() {
    ServiceLoader<Application> applications = ServiceLoader.load(Application.class);
    System.out.println("Starting applications");
    for (Application application : applications) {
      application.start();
    }
  }


  void registerPlugins() throws MalformedURLException {
    File pluginsFolder = new File(pluginsLocation);

    File[] plugins = pluginsFolder.listFiles(new FilenameFilter() {
      @Override
      public boolean accept(File dir, String name) {
        return name.endsWith(".jar");
      }
    });

    URL[] pluginUrls = new URL[plugins.length];
    for (int i = 0; i < pluginUrls.length; i++) {
      File pluginFile = plugins[i];
      System.out.println("Found plugin: " + pluginFile);
      pluginUrls[i] = pluginFile.toURI().toURL();
    }

    addToClassPathOf((URLClassLoader) Thread.currentThread().getContextClassLoader(), pluginUrls);
  }


  void addToClassPathOf(URLClassLoader urlClassLoader, URL... urls) {
    try {
      Method addUrlMethod = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
      addUrlMethod.setAccessible(true);
      for (URL url : urls) {
        try {
          addUrlMethod.invoke(urlClassLoader, url);
        } catch (Exception e) {
          System.err.println(String.format("could not add: %s to classpath", url));
        }
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}