Java tutorial
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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package net.gleamynode.conversion.support.discovery.tools; import java.util.Enumeration; import net.gleamynode.conversion.support.discovery.ResourceClass; import net.gleamynode.conversion.support.discovery.ResourceClassIterator; import net.gleamynode.conversion.support.discovery.ResourceNameIterator; import net.gleamynode.conversion.support.discovery.resource.ClassLoaders; import net.gleamynode.conversion.support.discovery.resource.classes.DiscoverClasses; import net.gleamynode.conversion.support.discovery.resource.names.DiscoverServiceNames; /** * [this was ServiceDiscovery12... the 1.1 versus 1.2 issue * has been abstracted to org.apache.commons.discover.jdk.JDKHooks] * * <p>Implement the JDK1.3 'Service Provider' specification. * ( http://java.sun.com/j2se/1.3/docs/guide/jar/jar.html ) * </p> * * This class supports any VM, including JDK1.1, via * org.apache.commons.discover.jdk.JDKHooks. * * The caller will first configure the discoverer by adding ( in the desired * order ) all the places to look for the META-INF/services. Currently * we support loaders. * * The findResources() method will check every loader. * * @author Richard A. Sitze * @author Craig R. McClanahan * @author Costin Manolache * @author James Strachan */ public class Service { /** Construct a new service discoverer */ protected Service() { } /** * as described in * sun/jdk1.3.1/docs/guide/jar/jar.html#Service Provider, * Except this uses <code>Enumeration</code> * instead of <code>Interator</code>. * * @return Enumeration of class instances (<code>Object</code>) */ public static Enumeration providers(Class spiClass) { return providers(new SPInterface(spiClass), null); } /** * This version lets you specify constructor arguments.. * * @param spi SPI to look for and load. * @param classLoaders loaders to use in search. * If <code>null</code> then use ClassLoaders.getAppLoaders(). */ public static Enumeration providers(final SPInterface spi, ClassLoaders loaders) { if (loaders == null) { loaders = ClassLoaders.getAppLoaders(spi.getSPClass(), Service.class, true); } ResourceNameIterator servicesIter = (new DiscoverServiceNames(loaders)).findResourceNames(spi.getSPName()); final ResourceClassIterator services = (new DiscoverClasses(loaders)).findResourceClasses(servicesIter); return new Enumeration() { private Object object = null; public boolean hasMoreElements() { if (object == null) { object = getNextClassInstance(); } return object != null; } public Object nextElement() { Object obj = object; object = null; return obj; } private Object getNextClassInstance() { while (services.hasNext()) { ResourceClass info = services.nextResourceClass(); try { return spi.newInstance(info.loadClass()); } catch (Exception e) { // ignore } } return null; } }; } }