src/main/java/org/apache/sling/scripting/sightly/impl/engine/ExtensionRegistryService.java

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 ~ 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
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package org.apache.sling.scripting.sightly.impl.engine;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;

import org.apache.sling.commons.osgi.PropertiesUtil;
import org.apache.sling.scripting.sightly.extension.RuntimeExtension;
import org.osgi.framework.ServiceReference;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import org.osgi.service.component.annotations.ReferenceCardinality;
import org.osgi.service.component.annotations.ReferencePolicy;

/**
 * Aggregator for all runtime extensions.
 */
@Component(service = ExtensionRegistryService.class)
public class ExtensionRegistryService {

    private volatile Map<String, RuntimeExtension> mapping = new HashMap<>();
    private final Map<String, TreeSet<RuntimeExtensionReference>> extensions = new HashMap<>();

    public Map<String, RuntimeExtension> extensions() {
        return mapping;
    }

    @Reference(
            policy = ReferencePolicy.DYNAMIC,
            service = RuntimeExtension.class,
            cardinality = ReferenceCardinality.MULTIPLE
            )
    @SuppressWarnings("unused")
    protected void bindExtensionService(ServiceReference<RuntimeExtension> serviceReference, RuntimeExtension runtimeExtension) {
        RuntimeExtensionReference rer = new RuntimeExtensionReference(serviceReference, runtimeExtension);
        synchronized (extensions) {
            Set<RuntimeExtensionReference> namedExtensions = extensions.computeIfAbsent(rer.getName(), key -> new TreeSet<>());
            if (namedExtensions.add(rer)) {
                mapping = getRuntimeExtensions();
            }
        }
    }

    @SuppressWarnings("unused")
    protected void unbindExtensionService(ServiceReference<RuntimeExtension> serviceReference) {
        synchronized (extensions) {
            String name = PropertiesUtil.toString(serviceReference.getProperty(RuntimeExtension.NAME), "");
            Set<RuntimeExtensionReference> namedExtensions = extensions.get(name);
            boolean changed = false;
            if (namedExtensions != null) {
                for (RuntimeExtensionReference runtimeExtensionReference : namedExtensions) {
                    if (serviceReference.equals(runtimeExtensionReference.getServiceReference())) {
                        namedExtensions.remove(runtimeExtensionReference);
                        if (namedExtensions.isEmpty()) {
                            extensions.remove(name);
                        }
                        changed = true;
                        break;
                    }
                }
            }
            if (changed) {
                mapping = getRuntimeExtensions();
            }
        }
    }

    private Map<String, RuntimeExtension> getRuntimeExtensions() {
        HashMap<String, RuntimeExtension> replacement = new HashMap<>();
        for (Map.Entry<String, TreeSet<RuntimeExtensionReference>> entry : extensions.entrySet()) {
            replacement.put(entry.getKey(), entry.getValue().last().getService());
        }
        return Collections.unmodifiableMap(replacement);
    }


}