Java tutorial
/* 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.activiti.content.engine; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.io.StringWriter; import java.lang.reflect.Method; import java.net.MalformedURLException; import java.net.URL; import java.util.ArrayList; import java.util.Enumeration; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set; import org.activiti.content.engine.impl.util.ReflectUtil; import org.activiti.engine.ActivitiException; import org.activiti.engine.EngineInfo; import org.apache.commons.io.IOUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public abstract class ContentEngines { private static Logger log = LoggerFactory.getLogger(ContentEngines.class); public static final String NAME_DEFAULT = "default"; protected static boolean isInitialized; protected static Map<String, ContentEngine> contentEngines = new HashMap<String, ContentEngine>(); protected static Map<String, EngineInfo> contentEngineInfosByName = new HashMap<String, EngineInfo>(); protected static Map<String, EngineInfo> contentEngineInfosByResourceUrl = new HashMap<String, EngineInfo>(); protected static List<EngineInfo> contentEngineInfos = new ArrayList<EngineInfo>(); /** * Initializes all dmn engines that can be found on the classpath for resources <code>activiti.dmn.cfg.xml</code> and for resources <code>activiti-dmn-context.xml</code> (Spring style * configuration). */ public synchronized static void init() { if (!isInitialized()) { if (contentEngines == null) { // Create new map to store content engines if current map is null contentEngines = new HashMap<String, ContentEngine>(); } ClassLoader classLoader = ContentEngines.class.getClassLoader(); Enumeration<URL> resources = null; try { resources = classLoader.getResources("activiti.content.cfg.xml"); } catch (IOException e) { throw new ActivitiException( "problem retrieving activiti.content.cfg.xml resources on the classpath: " + System.getProperty("java.class.path"), e); } // Remove duplicated configuration URL's using set. Some // classloaders may return identical URL's twice, causing duplicate startups Set<URL> configUrls = new HashSet<URL>(); while (resources.hasMoreElements()) { configUrls.add(resources.nextElement()); } for (Iterator<URL> iterator = configUrls.iterator(); iterator.hasNext();) { URL resource = iterator.next(); log.info("Initializing content engine using configuration '{}'", resource.toString()); initContentEngineFromResource(resource); } try { resources = classLoader.getResources("activiti-content-context.xml"); } catch (IOException e) { throw new ActivitiException( "problem retrieving activiti-content-context.xml resources on the classpath: " + System.getProperty("java.class.path"), e); } while (resources.hasMoreElements()) { URL resource = resources.nextElement(); log.info("Initializing content engine using Spring configuration '{}'", resource.toString()); initContentEngineFromSpringResource(resource); } setInitialized(true); } else { log.info("Content engines already initialized"); } } protected static void initContentEngineFromSpringResource(URL resource) { try { Class<?> springConfigurationHelperClass = ReflectUtil .loadClass("org.activiti.content.spring.SpringContentConfigurationHelper"); Method method = springConfigurationHelperClass.getDeclaredMethod("buildContentEngine", new Class<?>[] { URL.class }); ContentEngine contentEngine = (ContentEngine) method.invoke(null, new Object[] { resource }); String contentEngineName = contentEngine.getName(); EngineInfo contentEngineInfo = new EngineInfo(contentEngineName, resource.toString(), null); contentEngineInfosByName.put(contentEngineName, contentEngineInfo); contentEngineInfosByResourceUrl.put(resource.toString(), contentEngineInfo); } catch (Exception e) { throw new ActivitiException("couldn't initialize content engine from spring configuration resource " + resource.toString() + ": " + e.getMessage(), e); } } /** * Registers the given content engine. No {@link ContentEngineInfo} will be available for this content engine. An engine that is registered will be closed when the {@link ContentEngines#destroy()} is called. */ public static void registerContentEngine(ContentEngine contentEngine) { contentEngines.put(contentEngine.getName(), contentEngine); } /** * Unregisters the given dmn engine. */ public static void unregister(ContentEngine formEngine) { contentEngines.remove(formEngine.getName()); } private static EngineInfo initContentEngineFromResource(URL resourceUrl) { EngineInfo contentEngineInfo = contentEngineInfosByResourceUrl.get(resourceUrl.toString()); // if there is an existing dmn engine info if (contentEngineInfo != null) { // remove that dmn engine from the member fields contentEngineInfos.remove(contentEngineInfo); if (contentEngineInfo.getException() == null) { String contentEngineName = contentEngineInfo.getName(); contentEngines.remove(contentEngineName); contentEngineInfosByName.remove(contentEngineName); } contentEngineInfosByResourceUrl.remove(contentEngineInfo.getResourceUrl()); } String resourceUrlString = resourceUrl.toString(); try { log.info("initializing content engine for resource {}", resourceUrl); ContentEngine contentEngine = buildFormEngine(resourceUrl); String contentEngineName = contentEngine.getName(); log.info("initialised content engine {}", contentEngineName); contentEngineInfo = new EngineInfo(contentEngineName, resourceUrlString, null); contentEngines.put(contentEngineName, contentEngine); contentEngineInfosByName.put(contentEngineName, contentEngineInfo); } catch (Throwable e) { log.error("Exception while initializing content engine: {}", e.getMessage(), e); contentEngineInfo = new EngineInfo(null, resourceUrlString, getExceptionString(e)); } contentEngineInfosByResourceUrl.put(resourceUrlString, contentEngineInfo); contentEngineInfos.add(contentEngineInfo); return contentEngineInfo; } private static String getExceptionString(Throwable e) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); e.printStackTrace(pw); return sw.toString(); } protected static ContentEngine buildFormEngine(URL resource) { InputStream inputStream = null; try { inputStream = resource.openStream(); ContentEngineConfiguration contentEngineConfiguration = ContentEngineConfiguration .createContentEngineConfigurationFromInputStream(inputStream); return contentEngineConfiguration.buildContentEngine(); } catch (IOException e) { throw new ActivitiException("couldn't open resource stream: " + e.getMessage(), e); } finally { IOUtils.closeQuietly(inputStream); } } /** Get initialization results. */ public static List<EngineInfo> getContentEngineInfos() { return contentEngineInfos; } /** * Get initialization results. Only info will we available for form engines which were added in the {@link ContentEngines#init()}. No {@link FormEngineInfo} is available for engines which were * registered programmatically. */ public static EngineInfo getContentEngineInfo(String contentEngineName) { return contentEngineInfosByName.get(contentEngineName); } public static ContentEngine getDefaultContentEngine() { return getContentEngine(NAME_DEFAULT); } /** * obtain a content engine by name. * * @param contentEngineName * is the name of the content engine or null for the default content engine. */ public static ContentEngine getContentEngine(String contentEngineName) { if (!isInitialized()) { init(); } return contentEngines.get(contentEngineName); } /** * retries to initialize a content engine that previously failed. */ public static EngineInfo retry(String resourceUrl) { log.debug("retying initializing of resource {}", resourceUrl); try { return initContentEngineFromResource(new URL(resourceUrl)); } catch (MalformedURLException e) { throw new ActivitiException("invalid url: " + resourceUrl, e); } } /** * provides access to content engine to application clients in a managed server environment. */ public static Map<String, ContentEngine> getContentEngines() { return contentEngines; } /** * closes all dmn engines. This method should be called when the server shuts down. */ public synchronized static void destroy() { if (isInitialized()) { Map<String, ContentEngine> engines = new HashMap<String, ContentEngine>(contentEngines); contentEngines = new HashMap<String, ContentEngine>(); for (String contentEngineName : engines.keySet()) { ContentEngine contentEngine = engines.get(contentEngineName); try { contentEngine.close(); } catch (Exception e) { log.error("exception while closing {}", (contentEngineName == null ? "the default content engine" : "content engine " + contentEngineName), e); } } contentEngineInfosByName.clear(); contentEngineInfosByResourceUrl.clear(); contentEngineInfos.clear(); setInitialized(false); } } public static boolean isInitialized() { return isInitialized; } public static void setInitialized(boolean isInitialized) { ContentEngines.isInitialized = isInitialized; } }