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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.tuscany.sca.extensibility;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* Service discovery for Tuscany based on J2SE Jar service provider spec.
* Services are described using configuration files in META-INF/services.
* Service description specifies a class name followed by optional properties.
*
*
* @version $Rev$ $Date$
*/
public final class ServiceDiscovery implements ServiceDiscoverer {
private final static ServiceDiscovery INSTANCE = new ServiceDiscovery();
private ServiceDiscoverer discoverer;
private ServiceDiscovery() {
super();
}
/**
* Get an instance of Service discovery, one instance is created per
* ClassLoader that this class is loaded from
*
* @return
*/
public static ServiceDiscovery getInstance() {
return INSTANCE;
}
public ServiceDiscoverer getServiceDiscoverer() {
if (discoverer != null) {
return discoverer;
}
try {
// FIXME: This is a hack to trigger the activation of the extensibility-equinox bundle in OSGi
Class.forName("org.apache.tuscany.sca.extensibility.equinox.EquinoxServiceDiscoverer");
if (discoverer != null) {
return discoverer;
}
} catch (Throwable e) {
}
discoverer = new ContextClassLoaderServiceDiscoverer();
return discoverer;
}
public void setServiceDiscoverer(ServiceDiscoverer sd) {
if (discoverer != null) {
throw new IllegalStateException("The ServiceDiscoverer cannot be reset");
}
discoverer = sd;
}
public Collection<ServiceDeclaration> getServiceDeclarations(String name) throws IOException {
return getServiceDeclarations(name, false);
}
public Collection<ServiceDeclaration> getServiceDeclarations(String name, boolean byRanking) throws IOException {
Collection<ServiceDeclaration> declarations = getServiceDiscoverer().getServiceDeclarations(name);
if (!byRanking) {
return declarations;
}
if (!declarations.isEmpty()) {
List<ServiceDeclaration> declarationList = new ArrayList<ServiceDeclaration>(declarations);
Collections.sort(declarationList, ServiceComparator.DESCENDING_ORDER);
return declarationList;
} else {
return Collections.emptyList();
}
}
/**
* Get the service declaration. If there are more than one services, the one with highest ranking will
* be returned.
*/
public ServiceDeclaration getServiceDeclaration(final String name) throws IOException {
// ServiceDeclaration service = getServiceDiscoverer().getFirstServiceDeclaration(name);
// return service;
Collection<ServiceDeclaration> declarations = getServiceDeclarations(name, true);
if (!declarations.isEmpty()) {
List<ServiceDeclaration> declarationList = new ArrayList<ServiceDeclaration>(declarations);
Collections.sort(declarationList, ServiceComparator.DESCENDING_ORDER);
return declarationList.get(0);
} else {
return null;
}
}
/**
* Compare service declarations by ranking
*/
private static class ServiceComparator implements Comparator<ServiceDeclaration> {
private final static Comparator<ServiceDeclaration> DESCENDING_ORDER = new ServiceComparator();
public int compare(ServiceDeclaration o1, ServiceDeclaration o2) {
int rank1 = 0;
String r1 = o1.getAttributes().get("ranking");
if (r1 != null) {
rank1 = Integer.parseInt(r1);
}
int rank2 = 0;
String r2 = o2.getAttributes().get("ranking");
if (r2 != null) {
rank2 = Integer.parseInt(r2);
}
return rank2 - rank1; // descending
}
}
}
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