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.form.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.engine.ActivitiException; import org.activiti.engine.EngineInfo; import org.activiti.form.engine.impl.util.ReflectUtil; import org.apache.commons.io.IOUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public abstract class FormEngines { private static Logger log = LoggerFactory.getLogger(FormEngines.class); public static final String NAME_DEFAULT = "default"; protected static boolean isInitialized; protected static Map<String, FormEngine> formEngines = new HashMap<String, FormEngine>(); protected static Map<String, EngineInfo> formEngineInfosByName = new HashMap<String, EngineInfo>(); protected static Map<String, EngineInfo> formEngineInfosByResourceUrl = new HashMap<String, EngineInfo>(); protected static List<EngineInfo> formEngineInfos = 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 (formEngines == null) { // Create new map to store dmn engines if current map is null formEngines = new HashMap<String, FormEngine>(); } ClassLoader classLoader = FormEngines.class.getClassLoader(); Enumeration<URL> resources = null; try { resources = classLoader.getResources("activiti.form.cfg.xml"); } catch (IOException e) { throw new ActivitiException("problem retrieving activiti.form.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 form engine using configuration '{}'", resource.toString()); initFormEngineFromResource(resource); } try { resources = classLoader.getResources("activiti-form-context.xml"); } catch (IOException e) { throw new ActivitiException( "problem retrieving activiti-form-context.xml resources on the classpath: " + System.getProperty("java.class.path"), e); } while (resources.hasMoreElements()) { URL resource = resources.nextElement(); log.info("Initializing form engine using Spring configuration '{}'", resource.toString()); initFormEngineFromSpringResource(resource); } setInitialized(true); } else { log.info("Form engines already initialized"); } } protected static void initFormEngineFromSpringResource(URL resource) { try { Class<?> springConfigurationHelperClass = ReflectUtil .loadClass("org.activiti.form.spring.SpringFormConfigurationHelper"); Method method = springConfigurationHelperClass.getDeclaredMethod("buildContentEngine", new Class<?>[] { URL.class }); FormEngine formEngine = (FormEngine) method.invoke(null, new Object[] { resource }); String formEngineName = formEngine.getName(); EngineInfo formEngineInfo = new EngineInfo(formEngineName, resource.toString(), null); formEngineInfosByName.put(formEngineName, formEngineInfo); formEngineInfosByResourceUrl.put(resource.toString(), formEngineInfo); } catch (Exception e) { throw new ActivitiException("couldn't initialize form engine from spring configuration resource " + resource.toString() + ": " + e.getMessage(), e); } } /** * Registers the given dmn engine. No {@link FormEngineInfo} will be available for this dmn engine. An engine that is registered will be closed when the {@link FormEngines#destroy()} is called. */ public static void registerFormEngine(FormEngine formEngine) { formEngines.put(formEngine.getName(), formEngine); } /** * Unregisters the given dmn engine. */ public static void unregister(FormEngine formEngine) { formEngines.remove(formEngine.getName()); } private static EngineInfo initFormEngineFromResource(URL resourceUrl) { EngineInfo formEngineInfo = formEngineInfosByResourceUrl.get(resourceUrl.toString()); // if there is an existing dmn engine info if (formEngineInfo != null) { // remove that dmn engine from the member fields formEngineInfos.remove(formEngineInfo); if (formEngineInfo.getException() == null) { String formEngineName = formEngineInfo.getName(); formEngines.remove(formEngineName); formEngineInfosByName.remove(formEngineName); } formEngineInfosByResourceUrl.remove(formEngineInfo.getResourceUrl()); } String resourceUrlString = resourceUrl.toString(); try { log.info("initializing dmn engine for resource {}", resourceUrl); FormEngine formEngine = buildFormEngine(resourceUrl); String formEngineName = formEngine.getName(); log.info("initialised form engine {}", formEngineName); formEngineInfo = new EngineInfo(formEngineName, resourceUrlString, null); formEngines.put(formEngineName, formEngine); formEngineInfosByName.put(formEngineName, formEngineInfo); } catch (Throwable e) { log.error("Exception while initializing form engine: {}", e.getMessage(), e); formEngineInfo = new EngineInfo(null, resourceUrlString, getExceptionString(e)); } formEngineInfosByResourceUrl.put(resourceUrlString, formEngineInfo); formEngineInfos.add(formEngineInfo); return formEngineInfo; } private static String getExceptionString(Throwable e) { StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw); e.printStackTrace(pw); return sw.toString(); } protected static FormEngine buildFormEngine(URL resource) { InputStream inputStream = null; try { inputStream = resource.openStream(); FormEngineConfiguration formEngineConfiguration = FormEngineConfiguration .createFormEngineConfigurationFromInputStream(inputStream); return formEngineConfiguration.buildFormEngine(); } 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> getFormEngineInfos() { return formEngineInfos; } /** * Get initialization results. Only info will we available for form engines which were added in the {@link FormEngines#init()}. No {@link FormEngineInfo} is available for engines which were * registered programmatically. */ public static EngineInfo getFormEngineInfo(String formEngineName) { return formEngineInfosByName.get(formEngineName); } public static FormEngine getDefaultFormEngine() { return getFormEngine(NAME_DEFAULT); } /** * obtain a dmn engine by name. * * @param dmnEngineName * is the name of the dmn engine or null for the default dmn engine. */ public static FormEngine getFormEngine(String formEngineName) { if (!isInitialized()) { init(); } return formEngines.get(formEngineName); } /** * retries to initialize a dmn engine that previously failed. */ public static EngineInfo retry(String resourceUrl) { log.debug("retying initializing of resource {}", resourceUrl); try { return initFormEngineFromResource(new URL(resourceUrl)); } catch (MalformedURLException e) { throw new ActivitiException("invalid url: " + resourceUrl, e); } } /** * provides access to dmn engine to application clients in a managed server environment. */ public static Map<String, FormEngine> getFormEngines() { return formEngines; } /** * closes all dmn engines. This method should be called when the server shuts down. */ public synchronized static void destroy() { if (isInitialized()) { Map<String, FormEngine> engines = new HashMap<String, FormEngine>(formEngines); formEngines = new HashMap<String, FormEngine>(); for (String formEngineName : engines.keySet()) { FormEngine formEngine = engines.get(formEngineName); try { formEngine.close(); } catch (Exception e) { log.error("exception while closing {}", (formEngineName == null ? "the default form engine" : "form engine " + formEngineName), e); } } formEngineInfosByName.clear(); formEngineInfosByResourceUrl.clear(); formEngineInfos.clear(); setInitialized(false); } } public static boolean isInitialized() { return isInitialized; } public static void setInitialized(boolean isInitialized) { FormEngines.isInitialized = isInitialized; } }