geronimo-jsonb_1.0_spec/src/main/java/javax/json/bind/spi/JsonbProvider.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 javax.json.bind.spi;

import javax.json.bind.JsonbBuilder;
import javax.json.bind.JsonbException;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.List;
import java.util.ServiceLoader;

public abstract class JsonbProvider {
    private static final String DEFAULT_PROVIDER = "org.apache.johnzon.jsonb.JohnzonProvider";

    public static JsonbProvider provider() {
        if (System.getSecurityManager() != null) {
            return AccessController.doPrivileged((PrivilegedAction<JsonbProvider>) () -> doLoadProvider(null));
        }
        return doLoadProvider(null);
    }

    public static JsonbProvider provider(final String providerFqn) {
        if (providerFqn == null) {
            throw new IllegalArgumentException();
        }

        if (System.getSecurityManager() != null) {
            return AccessController.doPrivileged((PrivilegedAction<JsonbProvider>) () -> doLoadProvider(providerFqn));
        }
        return doLoadProvider(providerFqn);
    }

    private static JsonbProvider doLoadProvider(final String providerFqn) {

        final ClassLoader tccl = Thread.currentThread().getContextClassLoader();
        try {
            final Class<?> clazz = Class.forName("org.apache.geronimo.osgi.locator.ProviderLocator");
            final Method getServices = clazz.getDeclaredMethod("getServices", String.class, Class.class, ClassLoader.class);
            final List<JsonbProvider> osgiProviders = (List<JsonbProvider>) getServices.invoke(null, JsonbProvider.class.getName(), JsonbProvider.class, tccl);
            if (osgiProviders != null && !osgiProviders.isEmpty()) {
                return osgiProviders.iterator().next();
            }
        } catch (final Throwable e) {
            // locator not available, try normal mode
        }

        for (final JsonbProvider provider : ServiceLoader.load(JsonbProvider.class)) {
            if (providerFqn == null) {
                return provider;
            }
            else if (providerFqn.equals(provider.getClass().getName())) {
                return provider;
            }
        }

        if (providerFqn != null) {
            final String msg = providerFqn + " not found";
            throw new JsonbException(msg, new ClassNotFoundException(msg));
        }

        try {
            return JsonbProvider.class.cast(Thread.currentThread().getContextClassLoader().loadClass(DEFAULT_PROVIDER).newInstance());
        } catch (final ClassNotFoundException cnfe) {
            throw new JsonbException(DEFAULT_PROVIDER + " not found", cnfe);
        } catch (final Exception x) {
            throw new JsonbException(DEFAULT_PROVIDER + " couldn't be instantiated: " + x, x);
        }
    }


    public abstract JsonbBuilder create();
}