ComponentDisabler.java

/*
 * #%L
 * ACS AEM Commons Bundle
 * %%
 * Copyright (C) 2014 Adobe
 * %%
 * Licensed 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.
 * #L%
 */
package com.adobe.acs.commons.util.impl;

import java.util.Arrays;
import java.util.Map;

import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.ConfigurationPolicy;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferencePolicyOption;
import org.apache.felix.scr.annotations.Service;
import org.apache.sling.commons.osgi.PropertiesUtil;
import org.osgi.service.event.Event;
import org.osgi.service.event.EventHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Component disabler service
 * 
 * In Apache Felix the state of components and services is not persisted across restarts of its containing bundle.
 * For example, when you have a Bundle S containing a service S, and you manually stop the service S; after a
 * deactivate and activate of the bundle the service S is up again.
 * 
 * This service allows you to specify the names of components, which shouldn't be running. Whenever an OSGI service event is
 * fired, which services checks the status of this components and stops them if required.
 * 
 * Note 1: The component is always started, but this service takes care, that it is stopped immediately after. So if a behaviour
 * you don't like already happens during the activation of this service, you cannot prevent it using the mechanism here.
 * 
 * Note 2: Using this service should always be considered as a workaround. The primary focus should be to fix the component
 * you want to disable, so it's no longer required to disable it. If this component is part of Adobe AEM please raise a Daycare 
 * ticket for it.
 * 
 *
 */
@org.apache.felix.scr.annotations.Component(immediate = true, metatype = true,
        label = "ACS AEM Commons - OSGI Component Disabler", description = "Disables components by configuration",
        policy = ConfigurationPolicy.REQUIRE)
@Service()
@Property(name = "event.topics", value = { "org/osgi/framework/BundleEvent/STARTED",
        "org/osgi/framework/ServiceEvent/REGISTERED" }, propertyPrivate = true)
public class ComponentDisabler implements EventHandler {

    private static final Logger log = LoggerFactory.getLogger(ComponentDisabler.class);

    @Reference(policyOption = ReferencePolicyOption.GREEDY)
    private ComponentDisablerDriver componentDisabler;

    @Property(label = "Disabled components", description = "The names of the components/services you want to disable",
            cardinality = Integer.MAX_VALUE)
    private static final String DISABLED_COMPONENTS = "components";

    private String[] disabledComponents;

    @Activate
    protected void activate(Map<String, Object> properties) {
        disabledComponents = PropertiesUtil.toStringArray(properties.get(DISABLED_COMPONENTS), new String[0]);
        handleEvent(null);
    }

    @Override
    public void handleEvent(Event event) {
        // We don't care about the event, we just need iterate all configured
        // components and try to disable them
        log.trace("Disabling components and services {}", Arrays.toString(disabledComponents));

        for (String component : disabledComponents) {
            componentDisabler.disable(component);
        }
    }
}