org.ops4j.pax.wicket.internal.DelegatingClassResolver Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of org.ops4j.pax.wicket.service Show documentation
Pax Wicket Service is an OSGi extension of the Wicket framework, allowing for dynamic loading and unloading of Wicket components and pageSources.
There is a newer version: 5.0.0
Show newest version
/**
 * Copyright OPS4J
 *
 * 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 org.ops4j.pax.wicket.internal;

import static org.ops4j.lang.NullArgumentException.validateNotEmpty;
import static org.ops4j.lang.NullArgumentException.validateNotNull;
import static org.ops4j.pax.wicket.api.Constants.APPLICATION_NAME;
import static org.osgi.framework.Constants.OBJECTCLASS;

import java.net.URL;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.wicket.application.IClassResolver;
import org.osgi.framework.BundleContext;
import org.osgi.framework.Filter;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public final class DelegatingClassResolver implements IClassResolver {

    private static final Logger LOGGER = LoggerFactory.getLogger(DelegatingClassResolver.class);

    private final BundleContext context;
    private final String applicationName;
    private final List resolvers;

    private ClassResolverTracker tracker;

    public DelegatingClassResolver(BundleContext context, String applicationName) throws IllegalArgumentException {
        validateNotNull(context, "context");
        validateNotEmpty(applicationName, "applicationName");
        this.context = context;
        this.applicationName = applicationName;
        resolvers = new ArrayList();
    }

    public final void intialize() throws IllegalStateException {
        synchronized (this) {
            if (tracker != null) {
                throw new IllegalStateException(
                    "DelegatingClassResolver [" + this + "] had been initialized.");
            }
            tracker = new ClassResolverTracker(context, applicationName);
            tracker.open();
        }
    }

    public void dispose() throws IllegalStateException {
        synchronized (this) {
            if (tracker == null) {
                throw new IllegalStateException(
                    "DelegatingClassResolver [" + this + "] had not been initialized.");
            }
            tracker.close();
            tracker = null;
        }
    }

    public Class resolveClass(final String classname) throws ClassNotFoundException {
        synchronized (resolvers) {
            LOGGER.trace("Try to resolve {} from {} resolvers", classname, resolvers.size());
            for (IClassResolver resolver : resolvers) {
                try {
                    Class candidate = resolver.resolveClass(classname);
                    if (candidate != null) {
                        return candidate;
                    }
                } catch (ClassNotFoundException e) {
                    LOGGER.info("ClassResolver {} could not find class: {}", resolver, classname);
                } catch (RuntimeException e) {
                    LOGGER.warn("ClassResolver {} threw an unexpected exception.", resolver, e);
                }
            }
        }
        throw new ClassNotFoundException(String.format("Class [%s] can't be resolved.", classname));
    }

    public Iterator getResources(String name) {
        synchronized (resolvers) {
            ArrayList collectedResources = new ArrayList();
            for (IClassResolver resolver : resolvers) {
                try {
                    Iterator iterator = resolver.getResources(name);
                    if (iterator == null) {
                        continue;
                    }
                    while (iterator.hasNext()) {
                        collectedResources.add(iterator.next());
                    }
                } catch (RuntimeException e) {
                    LOGGER.warn("ClassResolver {} threw an unexpected exception.", resolver, e);
                    return collectedResources.iterator();
                }
            }
            return collectedResources.iterator();
        }
    }

    private final class ClassResolverTracker extends ServiceTracker {

        private final String m_applicationName;

        ClassResolverTracker(BundleContext context, String applicationName) {
            super(context, createFilter(context, applicationName), null);
            m_applicationName = applicationName;
        }

        @Override
        public final Object addingService(ServiceReference reference) {
            IClassResolver resolver = (IClassResolver) super.addingService(reference);
            synchronized (resolvers) {
                resolvers.add(resolver);
            }
            return resolver;
        }

        @Override
        public final void modifiedService(ServiceReference reference, Object service) {
            Object objAppName = reference.getProperty(APPLICATION_NAME);
            if (objAppName != null) {
                Class nameClass = objAppName.getClass();
                if (String.class.isAssignableFrom(nameClass)) {
                    if (!nameClass.isArray()) {
                        String appName = (String) objAppName;
                        if (m_applicationName.equals(appName)) {
                            return;
                        }
                    } else {
                        String[] appNames = (String[]) objAppName;
                        for (String appName : appNames) {
                            if (m_applicationName.equals(appName)) {
                                return;
                            }
                        }
                    }
                }
            }
            removedService(reference, service);
        }

        @Override
        public final void removedService(ServiceReference reference, Object service) {
            IClassResolver resolver = (IClassResolver) service;
            synchronized (resolvers) {
                resolvers.remove(resolver);
            }
            super.removedService(reference, service);
        }
    }

    private static Filter createFilter(BundleContext context, String applicationName) {
        String filterStr = "(&(" + OBJECTCLASS + "=" + IClassResolver.class.getName() + ")(" + APPLICATION_NAME + "="
                + applicationName + "))";
        try {
            return context.createFilter(filterStr);
        } catch (InvalidSyntaxException e) {
            String message = APPLICATION_NAME + "[" + applicationName + "] has an invalid format. ";
            throw new IllegalArgumentException(message);
        }
    }
}