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Contains the entire NEBA core implementation, i.e. the framework that interprets the NEBA API annotations and provides implementations for the service and lifecycle callback interfaces provided in the NEBA API. This package must not export anything as its implementation details are entirely private.

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/**
 * Copyright 2013 the original author or authors.
 * 
 * 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.
 **/

package io.neba.core.sling;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.resource.LoginException;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.api.resource.ResourceResolver;
import org.apache.sling.api.resource.ResourceResolverFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;

import javax.annotation.PreDestroy;

/**
 * Serves as a facade to
 * {@link ResourceResolverFactory#getAdministrativeResourceResolver(java.util.Map) administrative resource resolvers}.
 * Handles the lifecycle of the underlying {@link ResourceResolverFactory}, i.e.
 * re-obtains the administrative resolver when the factory changes.
 *
 * @author Olaf Otto
 */
@Service
public class AdministrativeResourceResolver {

    private final Logger logger = LoggerFactory.getLogger(getClass());

    private ResourceResolver resolver;

    public void bind(ResourceResolverFactory factory) throws LoginException {
        if (factory == null) {
            throw new IllegalArgumentException("Method argument resourceResolverFactory must not be null.");
        }
        this.resolver = factory.getAdministrativeResourceResolver(null);
    }

    /**
     * @param ignored can be null.
     * @see #closeResourceResolver()
     */
    public void unbind(@SuppressWarnings("unused") ResourceResolverFactory ignored) {
        closeResourceResolver();
    }

    /**
     * Closes and removes the reference to the current administrative resource resolver, as any resolver instance obtained
     * before a factory changed is malfunctioning, even if {@link ResourceResolver#isLive()} is true. Does
     * also discard the reference to the factory as it is a service proxy and may not be accessed before it is
     * {@link #bind(ResourceResolverFactory) bound} again, as this would result in a deadlock.
     */
    @PreDestroy
    public void closeResourceResolver() {
        if (this.resolver != null && this.resolver.isLive()) {
            this.resolver.close();
        }
        this.resolver = null;
    }

    /**
     * @see ResourceResolver#resolve(String)
     */
    public Resource resolve(String path) {
        return getResolver().resolve(path);
    }

    /**
     * @see org.apache.sling.api.resource.ResourceResolver#resolve(javax.servlet.http.HttpServletRequest, String)
     */
    public Resource resolve(SlingHttpServletRequest request, String path) {
        return getResolver().resolve(request, path);
    }

    /**
     * @see ResourceResolver#getResource(String)
     */
    public Resource get(String path) {
        return getResolver().getResource(path);
    }

    /**
     * Exposes the administrative resource resolver. Warning: The returned resource resolver
     * will seize to function if its factory changes and must thus not be retained.
     *
     * @return never null.
     */
    public ResourceResolver getResolver() {
        if (this.resolver == null) {
            // Logging and throwing is required since subsequent issues hide original exceptions thrown
            // in code synchronously executed in resource resolver factory re-starts.
            IllegalStateException e = new IllegalStateException(
                    "The resource resolver is unavailable - is resource resolution attempted during a resource resolver factory restart? " +
                    "Accessing a resource resolver factory while it is restarting is unsupported, as it would result in a deadlock.");
            logger.error("Unable to provide an administrative resource resolver.", e);
            throw e;
        }
        return resolver;
    }
}