WebResourceScriptCompilerProviderImpl.java

package org.apache.sling.webresource.impl;

import java.util.ArrayList;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.List;

import javax.jcr.Node;

import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.ReferencePolicy;
import org.apache.felix.scr.annotations.Service;
import org.apache.sling.webresource.WebResourceInventoryManager;
import org.apache.sling.webresource.WebResourceScriptCompiler;
import org.apache.sling.webresource.WebResourceScriptCompilerProvider;
import org.apache.sling.webresource.compiler.impl.AbstractNoOpCompiler;
import org.apache.sling.webresource.exception.WebResourceCompilerNotFoundException;
import org.osgi.service.event.Event;
import org.osgi.service.event.EventAdmin;

@Component(label = "Web Resource Compiler Provider Service", immediate = true)
@Service
@Reference(name = "WebResourceCompilerProvider", referenceInterface = WebResourceScriptCompiler.class, cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE, policy = ReferencePolicy.DYNAMIC)
public class WebResourceScriptCompilerProviderImpl implements
		WebResourceScriptCompilerProvider {

	private List<WebResourceScriptCompiler> webResourceScriptCompilerList = new ArrayList<WebResourceScriptCompiler>();

	private WebResourceScriptCompiler[] webResourceScriptCompilers;

	@Reference
	private EventAdmin eventAdmin;

	public WebResourceScriptCompiler getWebResourceCompilerForNode(
			Node sourceNode) throws WebResourceCompilerNotFoundException {
		WebResourceScriptCompiler result = null;

		WebResourceScriptCompiler[] serviceProviders = getWebResourceCompilerProviders();

		if (serviceProviders != null) {
			for (WebResourceScriptCompiler currentService : serviceProviders) {
				// Select the first service that can compile a web resource with
				// this
				// extension
				if (currentService.canCompileNode(sourceNode)) {
					result = currentService;
					break;
				}
			}
		}

		if (result == null) {
			throw new WebResourceCompilerNotFoundException(
					"No Compiler Found for this Web Resource Extension");
		}

		return result;
	}

	/**
	 * 
	 * Bind Compiler Providers
	 * 
	 * @param webResourceCompilerService
	 */
	protected void bindWebResourceCompilerProvider(
			WebResourceScriptCompiler webResourceCompilerService) {
		synchronized (this.webResourceScriptCompilerList) {
			this.webResourceScriptCompilerList.add(webResourceCompilerService);
			this.webResourceScriptCompilers = null;
		}

		if (!(webResourceCompilerService instanceof AbstractNoOpCompiler)) {
			Dictionary<String, Object> properties = new Hashtable<String, Object>();
			Event event = new Event(
					WebResourceInventoryManager.COMPILE_ALL_EVENT, properties);
			this.eventAdmin.postEvent(event);
		}
	}

	/**
	 * 
	 * Unbind Compiler Providers
	 * 
	 * @param webResourceCompilerService
	 */
	protected void unbindWebResourceCompilerProvider(
			WebResourceScriptCompiler webResourceCompilerService) {
		synchronized (this.webResourceScriptCompilerList) {
			this.webResourceScriptCompilerList
					.remove(webResourceCompilerService);
			this.webResourceScriptCompilers = null;
		}
	}

	/**
	 * 
	 * Return list of available compilers
	 * 
	 * @return
	 */
	private WebResourceScriptCompiler[] getWebResourceCompilerProviders() {
		WebResourceScriptCompiler[] list = this.webResourceScriptCompilers;

		if (list == null) {
			synchronized (this.webResourceScriptCompilerList) {
				this.webResourceScriptCompilers = this.webResourceScriptCompilerList
						.toArray(new WebResourceScriptCompiler[this.webResourceScriptCompilerList
								.size()]);
				list = this.webResourceScriptCompilers;
			}
		}

		return list;
	}

}