/*

  * Copyright 2000-2004 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.commons.scaffold.http;

 import java.io.BufferedInputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import java.util.Map;

 import java.util.Properties;

 import javax.servlet.ServletException;

 import javax.servlet.UnavailableException;

 import javax.servlet.http.HttpServlet;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 /**

  * Base servlet for loading application resources.

  * 

  * @author Ted Husted

  * @author Steve Raeburn

  */

 public class ResourceServlet extends HttpServlet {

     // TODO: Externalize messages using commons resources. 

     //       Previous suggestion was to use MessageResources, but this would 

     //       create a dependency on Struts. A better option would be to use 

     //       Commons Resources, which Struts will eventually migrate to.

     // ------------------------------------------------------- Class variables

     /**

      * Commons logging instance

      */

     private static Log log = LogFactory.getLog(ResourceServlet.class);

     // ------------------------------------------------------ Logging Messages

     private static final String INIT_FAILED_EVENT =

         "ResourceServlet: init() failed.";

     private static final String RELOAD_EVENT = 

         "Reloading ResourceServlet";

     private static final String DESTROY_EVENT = 

         "Destroying ResourceServlet";

     private static final String RESOURCE_LOADING =

         "Loading resources from path: ";

     private static final String RESOURCE_NOT_FOUND = 

         "Resources not found";

     // --------------------------------------------------- Parameter Utilities

     /**

      * Check for a parameter and returns a default value if not found.

      *

      * @param parameter The attribute name to look for

      * @param defaultValue The default to return if the parameter is not found

      * @return The customized value or the default value

      */

     public String getInitString(String parameter, String defaultValue) {

         String stringValue = getServletConfig().getInitParameter(parameter);

         if (null == stringValue)

             return defaultValue;

         return stringValue;

     }

     /**

      * Check for a parameter and returns a default value if not found,

      * or if the value does not convert to an <code>int</code>.

      *

      * @param parameter The attribute name to look for

      * @defaultValue The default to return if the parameter is not found

      * @return The customized value or the default value

      */

     public int getInitInt(String parameter, int defaultValue) {

         String stringValue = null;

         int intValue = defaultValue;

         try {

             stringValue = getServletConfig().getInitParameter(parameter);

             intValue = Integer.parseInt(stringValue);

         } catch (Throwable t) {

             intValue = defaultValue;

         }

         return intValue;

     }

     /**

      * Return a map of this servlet's initialization parameters.

      *

      * @return A map of this servlet's initialization parameters.

      * @fixme Not tested yet

      */

     public Map getInitParameters() {

         // :FIXME: Not tested yet.

         java.util.Enumeration names =

             getServletConfig().getInitParameterNames();

         java.util.HashMap map = new java.util.HashMap();

         while (names.hasMoreElements()) {

             String name = (String) names.nextElement();

             String value = getServletConfig().getInitParameter(name);

             map.put(name, value);

         }

         return map;

     }

     // --------------------------------------------------- Internal Properties

     /**

      * The parameter to check for a new path to the default properties

      * ["default"].

      */

     private static final String DEFAULT_PARAMETER = "default";

     /**

      * The default path to use if parameter is not set

      *["resources/default.properties"].

      */

     private static final String DEFAULT_PATH = "resources/default.properties";

     /**

      * The default attribute for the application properties.

      * The properties are exposed in the servlet context

      * under this attribute name

      * [lang.Tokens.PROPERTIES_KEY].

      */

     private static final String DEFAULT_ATTRIBUTE =

         org.apache.commons.scaffold.lang.Tokens.PROPERTIES_KEY;

     /**

      * Our default properties object.

      * <p>

      * The default properties can be used to store applications

      * settings that do not need to be localized and may

      * not even be displayed to the user.

      */

     Properties properties = null;

     /**

      * Set the default properties object.

      */

     public void setProperties(Properties properties) {

         this.properties = properties;

     }

     /**

      * Return the default properties object.

      *

      * @return The default properties object

      */

     public Properties getProperties() {

         return this.properties;

     }

     /**

      * A utility method for loading a Properties file

      * specified by an initialization parameter.

      *

      * The initialization parameter should specify the

      * package and folder for the Properties in system

      * path format (resources/custom.properties).

      *

      * @param parameter The name of the initialization

      * parameter

      * @param defaultPath The path to use if the

      * parameter is not found

      * @param attribute If not null, store in

      * application scope under this attribute name

      */

     public Properties loadProperties(

         String parameter,

         String defaultPath,

         String attribute)

         throws ServletException {

         String path = getInitString(parameter, defaultPath);

         if (log.isDebugEnabled()) {

             log.debug(RESOURCE_LOADING);

             log.debug(path);

         }

         InputStream is = null;

         is = this.getClass().getClassLoader().getResourceAsStream(path);

         if (null == is)

             throw new UnavailableException(RESOURCE_NOT_FOUND);

         Properties p = null;

         BufferedInputStream bis = new BufferedInputStream(is);

         try {

             p = new Properties();

             p.load(bis);

             bis.close();

             is.close();

         } catch (IOException e) {

             p = null;

         } finally {

             is = null;

             bis = null;

         }

         if ((null != p) && (null != attribute)) {

             this.getServletContext().setAttribute(attribute, p);

         }

         if (log.isDebugEnabled()) {

             log.debug(p.toString());

         }

         return p;

     }

     /**

      * Initialize the default properties for this application.

      * <p>

      * Use the <code>default</code> initialization parameter to specify

      * another path. Otherwise ["resources/default.properties"] is used.

      * <p>

      * If the default properties will not be used or specified,

      * override this method with one that does not try to load the

      * default properties.

      *

      * @exception IOException if an input/output error is encountered

      * @exception ServletException if we cannot initialize these resources

      * @todo The PROPERTIES_KEY could be made configurable,

      * but the BaseAction would need to be notified.

      */

     protected void initDefault() throws IOException, ServletException {

         setProperties(

             loadProperties(DEFAULT_PARAMETER, DEFAULT_PATH, DEFAULT_ATTRIBUTE));

     }

     /**

      * Release any default resources created at initialization

      */

     protected void destroyDefault() {

         setProperties(null);

     }

     // --------------------------------------------------- HttpServlet Methods

     /**

      * Initialize this servlet by caling three extension points:

      * <ul>

      * <li><code>initLogging</code></li>

      * <li><code>initDefault</code></li>

      * <li><code>initCustom</code></li>

      * </ul>

      * The main extension point is <code><b>initCustom</b></code>

      * The default implementation does nothing.

      * The other two methods have reasonable default behaviors that most

      * subclasses could use as-is.

      * This may be called again from <code>reload</code> and should be

      * "re-enterant".

      *

      * @exception ServletException if we cannot configure ourselves

      * correctly

      */

     public void init() throws ServletException {

         try {

             initDefault();

             // initMessages();

             initCustom();

         } catch (IOException e) {

             throw new UnavailableException(INIT_FAILED_EVENT);

         }

     }

     /**

      * Gracefully shut down this controller servlet, releasing any resources

      * that were allocated at initialization.

      */

     public void destroy() {

         if (log.isDebugEnabled()) {

             log.debug(DESTROY_EVENT);

         }

         destroyCustom();

         // destroyMessages();

         destroyDefault();

     }

     // ------------------------------------------------------ Extension Points

     /**

      * Initialize the custom properties or objects for this application.

      *

      * @exception IOException if an input/output error is encountered

      * @exception ServletException if we cannot initialize these resources

      */

     protected void initCustom() throws IOException, ServletException {

         // Override with custom initializations

     }

     /**

      * Release any custom resources created at initialization

      */

     protected void destroyCustom() {

         // override to provide functionality if needed

     }

     // -------------------------------------------------------- Public Methods

     /**

      * Reload the configuration of this controller servlet from our

      * underlying configuration files.

      *

      * @exception IOException if an input/output error occurs

      * @exception ServletException if a servlet exception occurs

      */

     public void reload() throws IOException, ServletException {

         if (log.isDebugEnabled()) {

             log.debug(RELOAD_EVENT);

         }

         // Re-initialize

         init();

     }

 } // end ResourceServlet