org.sakaiproject.vm.VelocityServlet.java Source code

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Here is the source code for org.sakaiproject.vm.VelocityServlet.java

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/**********************************************************************************
 * $URL$
 * $Id$
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 *
 * Copyright (c) 2003, 2004, 2005, 2006, 2008 The Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.
 *
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package org.sakaiproject.vm;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;

import javax.servlet.ServletConfig;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.collections.ExtendedProperties;
import org.apache.velocity.Template;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.tools.view.servlet.VelocityViewServlet;

/**
 * <p>
 * Responds with the expansion of a Velocity Template. The template and context references are specified in the request.
 * </p>
 */
public class VelocityServlet extends VelocityViewServlet {

    /**
     * Called by the VelocityServlet init(). We want to set a set of properties so that templates will be found in the webapp root. This makes this easier to work with as an example, so a new user doesn't have to worry about config issues when first
     * figuring things out
     */
    protected ExtendedProperties loadConfiguration(ServletConfig config) throws IOException, FileNotFoundException {
        // This is to support old config property.
        String configPath = config.getInitParameter("properties");
        ExtendedProperties p;
        if (configPath != null && configPath.length() > 0) {
            p = new ExtendedProperties();
            if (!configPath.startsWith("/")) {
                configPath = "/" + configPath;
            }
            p.load(getServletContext().getResourceAsStream(configPath));
        } else {
            // load the properties as configured in the servlet init params
            p = super.loadConfiguration(config);
        }

        /*
         * first, we set the template path for the FileResourceLoader to the root of the webapp. This probably won't work under in a WAR under WebLogic, but should under tomcat :)
         */

        String path = config.getServletContext().getRealPath("/");

        if (path == null) {
            getVelocityEngine().getLog().debug(" VelocityServlet.loadConfiguration() : unable to "
                    + "get the current webapp root.  Using '/'. Please fix.");
            path = "/";
        }

        p.setProperty(Velocity.FILE_RESOURCE_LOADER_PATH, path);

        /**
         * and the same for the log file
         */
        p.setProperty("runtime.log", path + p.getProperty("runtime.log"));

        return p;
    }

    /**
     * <p>
     * main routine to handle a request. Called by VelocityServlet, your responsibility as programmer is to simply return a valid Template
     * </p>
     * 
     * @param ctx
     *        a Velocity Context object to be filled with data. Will be used for rendering this template
     * @return Template to be used for request
     */
    public Template handleRequest(HttpServletRequest request, HttpServletResponse response, Context ctx) {
        // Note: Velocity doesn't like dots in the context names, so we change them to '_'

        // load the context with attributes
        Enumeration e = request.getAttributeNames();
        while (e.hasMoreElements()) {
            String name = (String) e.nextElement();
            String vName = escapeVmName(name);
            Object value = request.getAttribute(name);

            ctx.put(vName, value);
            // log("--> context (attribute): " + vName + " = " + value);
        }

        // if the javax.servlet.include.servlet_path attribute exists, use this value as the template
        String templatePath = (String) request.getAttribute("javax.servlet.include.servlet_path");

        // if not there, try our special include
        if (templatePath == null) {
            templatePath = (String) request.getAttribute("sakai.vm.path");
        }

        // if not there, use the servletpath
        if (templatePath == null) {
            templatePath = request.getServletPath();
        }

        Template template = null;
        try {
            // log("--> template path: " + templatePath);
            template = getTemplate(templatePath);
        } catch (ParseErrorException ex) {
            log("Exception reading vm template: " + templatePath + " " + ex);
        } catch (ResourceNotFoundException ex) {
            log("Exception reading vm template: " + templatePath + " " + ex);
        } catch (Exception ex) {
            log("Exception reading vm template: " + templatePath + " " + ex);
        }

        return template;

    } // handleRequest

    /**
     * Change any characters that Velocity doesn't like in the name to '_' to make a valid Velocity name
     * 
     * @param name
     *        The name to convert.
     * @return The name converted to a valid Velocity name.
     */
    protected String escapeVmName(String name) {
        char[] chars = name.toCharArray();

        // make sure first character is valid (alpha)
        if (!Character.isLetter(chars[0])) {
            chars[0] = 'X';
        }

        // replace any other invalid characters
        for (int i = 1; i < chars.length; i++) {
            char c = chars[i];
            if (!(Character.isLetterOrDigit(c) || (c == '_') || (c == '-'))) {
                chars[i] = '_';
            }
        }

        return new String(chars);

    } // escapeVmName

} // class VelocityServlet