Java tutorial
/** * Copyright (C) 2012 JBoss Inc * * 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.jbpm.formModeler.service.bb.mvc.controller; import org.apache.commons.lang3.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.jbpm.formModeler.service.Application; import org.jbpm.formModeler.service.bb.mvc.components.ControllerStatus; import org.jbpm.formModeler.service.bb.mvc.components.CurrentComponentRenderer; import org.jbpm.formModeler.service.bb.mvc.controller.responses.ShowCurrentScreenResponse; import org.jbpm.formModeler.service.error.ErrorManager; import org.jbpm.formModeler.service.error.ErrorReport; import org.jbpm.formModeler.service.error.ErrorReportHandler; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; /** * Application end point for HTTP requests. It provides the following features:<ul> * <li> Perform application initialization and ending. * <li> Analyze the requests received and dispatch to the proper execution method.</ul> */ public class ControllerServlet extends HttpServlet { private static transient Logger log = LoggerFactory.getLogger(ControllerServlet.class); public final static String INIT_PARAM_CFG_DIR = "base.cfg.dir"; public final static String INIT_PARAM_APP_DIR = "base.app.dir"; private static Application theApp; private static boolean initSuccess = true; private static Throwable initException; protected void initError() { // Write some data to file, allowing external checking of what went wrong. File outputFile = new File(Application.lookup().getBaseAppDirectory() + "/ControllerError.txt"); FileWriter writer = null; try { StringWriter sw = new StringWriter(); initException.printStackTrace(new PrintWriter(sw)); writer = new FileWriter(outputFile); writer.write(initException.getMessage() + "\n" + sw.toString()); outputFile.deleteOnExit(); sw.close(); } catch (IOException e1) { log.error("Error writing to log file: ", e1); } finally { if (writer != null) { try { writer.close(); } catch (IOException e2) { log.error("Error closing log file: ", e2); } } } } protected void initApp() throws ServletException { try { String baseAppDir = getInitParameter(INIT_PARAM_APP_DIR); if (baseAppDir == null) { baseAppDir = new File(getServletContext().getRealPath("/")).getPath(); baseAppDir = StringUtils.replace(baseAppDir, "\\", "/"); log.info("Application Directory: " + baseAppDir); } String baseCfgDir = getInitParameter(INIT_PARAM_CFG_DIR); if (baseCfgDir == null) { baseCfgDir = baseAppDir + "/WEB-INF/etc"; log.info("Application Config Directory: " + baseCfgDir); } theApp = Application.lookup(); theApp.setBaseAppDirectory(baseAppDir); theApp.setBaseCfgDirectory(baseCfgDir); theApp.start(); initSuccess = true; } catch (Throwable e) { log.error("Error initializing application. Marking it as uninitialized ", e); initException = e; initSuccess = false; initError(); } } /** * Process incoming HTTP requests * * @param request Object that encapsulates the request to the servlet. * @param response Object that encapsulates the response from the servlet. */ public final void service(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException { if (theApp == null) initApp(); if (initSuccess) { try { HTTPSettings settings = HTTPSettings.lookup(); request.setCharacterEncoding(settings.getEncoding()); } catch (UnsupportedEncodingException e) { log.error("Error: ", e); } // Init the request context. ControllerServletHelper helper = ControllerServletHelper.lookup(); synchronized (helper) { CommandRequest cmdRq = helper.initThreadLocal(request, response); ControllerStatus.lookup().setRequest(cmdRq); try { // Process the request (control layer) processTheRequest(cmdRq); // Render the view (presentation layer) processTheView(cmdRq); } finally { // Clear the request context. helper.clearThreadLocal(request, response); } } } else { log.error("Received request, but application servlet hasn't been properly initialized. Ignoring."); response.sendError(500, "Application incorrectly initialized."); } } protected void processTheRequest(CommandRequest request) { try { // Process the request. RequestProcessor.lookup().run(); // Ensure GETs URIs are fully processed. if ("GET".equalsIgnoreCase(request.getRequestObject().getMethod())) { ControllerStatus.lookup().compareConsumedUri(); } } catch (Throwable e) { // Display the error. displayTheError(e); } } protected void processTheView(CommandRequest request) { try { if (log.isDebugEnabled()) log.debug("Rendering response. Id=" + Thread.currentThread().getName()); CommandResponse cmdResponse = ControllerStatus.lookup().getResponse(); cmdResponse.execute(request); } catch (Throwable e) { log.error( "Error painting response. User might have seen something ugly in the browser if he is still there.", e); } } protected void displayTheError(Throwable t) { // Get the error generated during the thread's execution. ErrorReport report = ErrorManager.lookup().getErrorReport(); // Initialize the error handler bean. ErrorReportHandler errorHandler = ErrorReportHandler.lookup(); errorHandler.setWidth(1000); errorHandler.setHeight(400); errorHandler.setErrorReport(report); // Force the current screen to be refreshed so the error report will be displayed. CurrentComponentRenderer.lookup().setCurrentComponent(errorHandler); ControllerStatus controllerStatus = ControllerStatus.lookup(); controllerStatus.setResponse(new ShowCurrentScreenResponse()); } }