yoko-osgi/src/main/java/org/apache/yoko/osgi/locator/BundleProviderLoader.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
 * under the License.
 */


package org.apache.yoko.osgi.locator;

import org.osgi.framework.Bundle;

/**
 * Holder class for located services information.
 */
public class BundleProviderLoader implements Comparable<BundleProviderLoader> {
    // the class name for this provider
    private final String providerId;
    // the mapped class name of the provider.
    private final String providerClass;
    // the hosting bundle.
    private final Bundle bundle;

    private final int priority;

    /**
     * Create a loader for this registered provider.
     *
     * @param providerId The provider ID
     * @param providerClass The mapped class name of the provider.
     * @param bundle    The hosting bundle.
     * @param priority
     */
    public BundleProviderLoader(String providerId, String providerClass, Bundle bundle, int priority) {
        this.providerId = providerId;
        this.providerClass = providerClass;
        this.bundle = bundle;
        this.priority = priority;
    }

    /**
     * Load a provider class.
     *
     * @return The provider class from the target bundle.
     * @exception Exception
     */
    public Class<?> loadClass() throws ClassNotFoundException {
        try {
//                log(LogService.LOG_DEBUG, "loading class for: " + this);
            return bundle.loadClass(providerClass);
        } catch (ClassNotFoundException e) {
//                log(LogService.LOG_DEBUG, "exception caught while loading " + this, e);
            throw e;
        }
    }

    /**
     * Create an instance of the registred service.
     *
     * @return The created instance.  A new instance is created on each call.
     * @exception Exception
     */
    public Object createInstance() throws Exception {
        // get the class object
        Class <?> cls = loadClass();
        try {
            // just create an instance using the default constructor
            return cls.newInstance();
        } catch (Exception e) {
//                log(LogService.LOG_DEBUG, "exception caught while creating " + this, e);
            throw e;
        } catch (Error e) {
//                log(LogService.LOG_DEBUG, "error caught while creating " + this, e);
            throw e;
        }
    }


    public String id() {
        return providerId;
    }

    @Override
    public String toString() {
        return "Provider interface=" + providerId + " , provider class=" + providerClass + ", bundle=" + bundle;
    }

    @Override
    public int hashCode() {
        return providerId.hashCode() + providerClass.hashCode() + (int)bundle.getBundleId();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof BundleProviderLoader) {
            return providerId.equals(((BundleProviderLoader)obj).providerId) &&
                   providerClass.equals(((BundleProviderLoader)obj).providerClass) &&
                   bundle.getBundleId() == ((BundleProviderLoader)obj).bundle.getBundleId();
        } else {
            return false;
        }
    }

    public int compareTo(BundleProviderLoader other) {
        return other.priority - priority;
    }
}