Java tutorial
/* * \$Header\$ * \$Revision\$ * \$Date\$ * * Copyright 2004 The Apache Software Foundation. * * 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.apache.struts.chain.servlet; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.chain.Command; import org.apache.commons.chain.Context; import org.apache.commons.chain.web.servlet.ServletWebContext; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.struts.chain.Constants; import org.apache.struts.config.ForwardConfig; import org.apache.struts.tiles.ComponentContext; import org.apache.struts.tiles.ComponentDefinition; import org.apache.struts.tiles.Controller; import org.apache.struts.tiles.FactoryNotFoundException; import org.apache.struts.tiles.DefinitionsUtil; import org.apache.struts.tiles.TilesUtil; import org.apache.struts.upload.MultipartRequestWrapper; /** * <p>Command class intended to perform responsibilities of the * TilesRequestProcessor in Struts 1.1. Does not actually dispatch requests, * but simply prepares the chain context for a later forward as * appropriate. Should be added to a chain before something which * would handle a conventional ForwardConfig.</p> * * <p>This class will never have any effect on the chain unless a * <code>TilesDefinitionFactory</code> can be found; however it does not * consider the absence of a definition factory to be a fatal error; the * command simply returns false and lets the chain continue.</p> * * <p>To initialize the <code>TilesDefinitionFactory</code>, use * <code>org.apache.struts.chain.legacy.TilesPlugin</code>. This class * is a simple extension to <code>org.apache.struts.tiles.TilesPlugin</code> * which simply does not interfere with your choice of <code>RequestProcessor</code> * implementation. * </p> * * */ public class TilesPreProcessor implements Command { // ------------------------------------------------------ Instance Variables private static final Log log = LogFactory.getLog(TilesPreProcessor.class); private String forwardConfigKey = Constants.FORWARD_CONFIG_KEY; private String includeKey = Constants.INCLUDE_KEY; private String moduleConfigKey = Constants.MODULE_CONFIG_KEY; // -------------------------------------------------------------- Properties /** * <p>Return the context attribute key under which the * <code>ForwardConfig</code> for the currently selected application * action is stored.</p> */ public String getForwardConfigKey() { return (this.forwardConfigKey); } /** * <p>Set the context attribute key under which the * <code>ForwardConfig</code> for the currently selected application * action is stored.</p> * * @param forwardConfigKey The new context attribute key */ public void setForwardConfigKey(String forwardConfigKey) { this.forwardConfigKey = forwardConfigKey; } /** * <p>Return the context attribute key under which the * include uri for the currently selected application * action is stored.</p> */ public String getIncludeKey() { return (this.includeKey); } /** * <p>Set the context attribute key under which the * include uri for the currently selected application * action is stored.</p> * * @param includeKey The new context attribute key */ public void setIncludeKey(String includeKey) { this.includeKey = includeKey; } // ---------------------------------------------------------- Public Methods /** * <p>If the current <code>ForwardConfig</code> is using "tiles", * perform necessary pre-processing to set up the <code>TilesContext</code> * and substitute a new <code>ForwardConfig</code> which is understandable * to a <code>RequestDispatcher</code>.</p> * * <p>Note that if the command finds a previously existing * <code>ComponentContext</code> in the request, then it * infers that it has been called from within another tile, * so instead of changing the <code>ForwardConfig</code> in the chain * <code>Context</code>, the command uses <code>RequestDispatcher</code> * to <em>include</em> the tile, and returns true, indicating that the processing * chain is complete.</p> * * @param context The <code>Context</code> for the current request * * @return <code>false</code> in most cases, but true if we determine * that we're processing in "include" mode. */ public boolean execute(Context context) throws Exception { // Is there a Tiles Definition to be processed? ForwardConfig forwardConfig = (ForwardConfig) context.get(getForwardConfigKey()); if (forwardConfig == null || forwardConfig.getPath() == null) { log.debug("No forwardConfig or no path, so pass to next command."); return (false); } ServletWebContext swcontext = (ServletWebContext) context; ComponentDefinition definition = null; try { definition = TilesUtil.getDefinition(forwardConfig.getPath(), swcontext.getRequest(), swcontext.getContext()); } catch (FactoryNotFoundException ex) { // this is not a serious error, so log at low priority log.debug("Tiles DefinitionFactory not found, so pass to next command."); return false; } // Do we do a forward (original behavior) or an include ? boolean doInclude = false; ComponentContext tileContext = null; // Get current tile context if any. // If context exists, we will do an include tileContext = ComponentContext.getContext(swcontext.getRequest()); doInclude = (tileContext != null); // Controller associated to a definition, if any Controller controller = null; // Computed uri to include String uri = null; if (definition != null) { // We have a "forward config" definition. // We use it to complete missing attribute in context. // We also get uri, controller. uri = definition.getPath(); controller = definition.getOrCreateController(); if (tileContext == null) { tileContext = new ComponentContext(definition.getAttributes()); ComponentContext.setContext(tileContext, swcontext.getRequest()); } else { tileContext.addMissing(definition.getAttributes()); } } // Process definition set in Action, if any. This may override the // values for uri or controller found using the ForwardConfig, and // may augment the tileContext with additional attributes. // :FIXME: the class DefinitionsUtil is deprecated, but I can't find // the intended alternative to use. definition = DefinitionsUtil.getActionDefinition(swcontext.getRequest()); if (definition != null) { // We have a definition. // We use it to complete missing attribute in context. // We also overload uri and controller if set in definition. if (definition.getPath() != null) { log.debug("Override forward uri " + uri + " with action uri " + definition.getPath()); uri = definition.getPath(); } if (definition.getOrCreateController() != null) { log.debug("Override forward controller with action controller"); controller = definition.getOrCreateController(); } if (tileContext == null) { tileContext = new ComponentContext(definition.getAttributes()); ComponentContext.setContext(tileContext, swcontext.getRequest()); } else { tileContext.addMissing(definition.getAttributes()); } } if (uri == null) { log.debug("no uri computed, so pass to next command"); return false; } // Execute controller associated to definition, if any. if (controller != null) { log.trace("Execute controller: " + controller); controller.execute(tileContext, swcontext.getRequest(), swcontext.getResponse(), swcontext.getContext()); } // If request comes from a previous Tile, do an include. // This allows to insert an action in a Tile. if (doInclude) { log.info("Tiles process complete; doInclude with " + uri); doInclude(swcontext, uri); return (true); } else { // create an "instant" forward config which can be used // by an AbstractPerformForward later as if our ForwardConfig // were the one actually returned by an executing Action log.info("Tiles process complete; forward to " + uri); // :FIXME: How do we need to coordinate the "context-relative" value // with other places it might be set. For now, hardcode to true. context.put(getForwardConfigKey(), new ForwardConfig("tiles-chain", uri, false, true)); return (false); } } // ------------------------------------------------------- Protected Methods /** * <p>Do an include of specified URI using a <code>RequestDispatcher</code>.</p> * * @param swcontext a chain servlet/web context * @param uri Context-relative URI to include */ protected void doInclude(ServletWebContext swcontext, String uri) throws IOException, ServletException { HttpServletRequest request = swcontext.getRequest(); // Unwrap the multipart request, if there is one. if (request instanceof MultipartRequestWrapper) { request = ((MultipartRequestWrapper) request).getRequest(); } HttpServletResponse response = swcontext.getResponse(); RequestDispatcher rd = swcontext.getContext().getRequestDispatcher(uri); if (rd == null) { response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Error getting RequestDispatcher for " + uri); return; } rd.include(request, response); } }