/*
* Copyright 2007-2008 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 org.impalaframework.osgi.startup;
import java.net.URL;
import java.util.List;
import org.impalaframework.osgi.spring.ImpalaOsgiApplicationContext;
import org.impalaframework.osgi.util.OsgiUtils;
import org.impalaframework.startup.ContextStarter;
import org.osgi.framework.BundleContext;
import org.springframework.context.ApplicationContext;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.osgi.context.BundleContextAware;
import org.springframework.osgi.context.support.OsgiBundleXmlApplicationContext;
import org.springframework.osgi.util.BundleDelegatingClassLoader;
import org.springframework.util.Assert;
/**
* Implementation of {@link ContextStarter} designed to bootstrap Impala in
* an OSGi environment.
*/
public class OsgiContextStarter implements ContextStarter, BundleContextAware {
private BundleContext bundleContext;
public void setBundleContext(BundleContext bundleContext) {
this.bundleContext = bundleContext;
}
/**
* Finds bundle resources corresponding with the specified location list.
* Unlike {@link OsgiBundleXmlApplicationContext}, finds resources not just in the host
* bundle but in any bundle which contains the locations. Uses the host bundle's class
* loader as the Thread's context class loader during the {@link ApplicationContext}
* startup cycle.
*/
public ApplicationContext startContext(List<String> locations) {
Assert.notNull(locations);
Thread currentThread = Thread.currentThread();
ClassLoader oldTCCL = currentThread.getContextClassLoader();
try {
ClassLoader classLoader =
BundleDelegatingClassLoader.createBundleClassLoaderFor(bundleContext.getBundle());
currentThread.setContextClassLoader(classLoader);
final Resource[] resources = getResourcesForLocations(locations);
return newApplicationContext(resources);
} finally {
currentThread.setContextClassLoader(oldTCCL);
}
}
private Resource[] getResourcesForLocations(List<String> locations) {
//should cycle through bundles in reverse, so that most recently
//loaded bundles are encountered first. However, does
//not guarantee that any resource is loaded from any particular bundle.
//Instead, relies on sensible naming conventions for Impala bootstrap bundles.
URL[] urls = OsgiUtils.findResources(bundleContext, locations.toArray(new String[locations.size()]));
Resource[] resources = new Resource[urls.length];
for (int i = 0; i < resources.length; i++) {
resources[i] = new UrlResource(urls[i]);
}
return resources;
}
private ApplicationContext newApplicationContext(Resource[] resources) {
ImpalaOsgiApplicationContext applicationContext = new ImpalaOsgiApplicationContext();
applicationContext.setConfigResources(resources);
applicationContext.setBundleContext(bundleContext);
applicationContext.refresh();
return applicationContext;
}
}