ServiceLoader.java

package net.java.dev.weblets.util;

import net.java.dev.weblets.WebletException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * Service loader class, this is the central binding controller for our api and impl parts
 * 
 */
public class ServiceLoader {
	public static Class loadService(Class serviceRef) {
		BufferedReader reader = null;
		try {
			ClassLoader loader = Thread.currentThread().getContextClassLoader();
			String resource = "META-INF/services/" + serviceRef.getName();
			InputStream in = loader.getResourceAsStream(resource);
			if (in == null) { // we are in a different loader, some ear containers are at the ear level at this stage if it is a webapp context
				loader = serviceRef.getClassLoader();
				in = loader.getResourceAsStream(resource);
				if (in == null) {
					Log log = LogFactory.getLog(ServiceLoader.class);
					log.error(serviceRef + " Implementation class could not be found");
					// lets bomb out afterwards!!!
				}
			}
			reader = new BufferedReader(new InputStreamReader(in));
			String serviceClassName = reader.readLine();
			return loader.loadClass(serviceClassName);
		} catch (IOException e) {
			throw new WebletException("Error reading Weblet Service " + "service information " + serviceRef, e);
		} catch (ClassNotFoundException e) {
			throw new WebletException("Unable to load Weblet Service " + "implementation class " + serviceRef, e);
		} finally {
			if (reader != null)
				try {
					reader.close();
				} catch (IOException e) {
					throw new WebletException("Unable to load Weblet Service " + serviceRef, e);
				}
		}
	}

	public static Class loadService(String serviceRef) {
		BufferedReader reader = null;
		try {
			ClassLoader loader = Thread.currentThread().getContextClassLoader();
			String resource = "META-INF/services/" + serviceRef;
			InputStream in = loader.getResourceAsStream(resource);
			if (in == null) { // we are in a different loader, some ear containers are at the ear level at this stage if it is a webapp context
				loader = ServiceLoader.class.getClassLoader();
				in = loader.getResourceAsStream(resource);
				if (in == null) {
					Log log = LogFactory.getLog(ServiceLoader.class);
					log.error(serviceRef + " Implementation class could not be found");
					// lets bomb out afterwards!!!
				}
			}
			reader = new BufferedReader(new InputStreamReader(in));
			String serviceClassName = reader.readLine();
			return loader.loadClass(serviceClassName);
		} catch (IOException e) {
			throw new WebletException("Error reading Weblet Service " + "service information " + serviceRef, e);
		} catch (ClassNotFoundException e) {
			throw new WebletException("Unable to load Weblet Service " + "implementation class " + serviceRef, e);
		} finally {
			if (reader != null)
				try {
					reader.close();
				} catch (IOException e) {
					throw new WebletException("Unable to load Weblet Service " + serviceRef, e);
				}
		}
	}
}