velocityviewservlet.java

一个用于java web页面开发的开源包

package org.apache.velocity.tools.view.servlet;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.collections.ExtendedProperties;
import org.apache.commons.lang.StringEscapeUtils;
import org.apache.velocity.Template;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.io.VelocityWriter;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.tools.generic.log.LogSystemCommonsLog;
import org.apache.velocity.tools.view.ToolboxManager;
import org.apache.velocity.tools.view.context.ChainedContext;
import org.apache.velocity.util.SimplePool;


/**
 * <p>A servlet to process Velocity templates. This is comparable to the
 * the JspServlet for JSP-based applications.</p>
 *
 * <p>The servlet provides the following features:</p>
 * <ul>
 *   <li>renders Velocity templates</li>
 *   <li>provides support for an auto-loaded, configurable toolbox</li>
 *   <li>provides transparent access to the servlet request attributes,
 *       servlet session attributes and servlet context attributes by
 *       auto-searching them</li>
 *   <li>logs to the logging facility of the servlet API</li>
 * </ul>
 *
 * <p>VelocityViewServlet supports the following configuration parameters
 * in web.xml:</p>
 * <dl>
 *   <dt>org.apache.velocity.toolbox</dt>
 *   <dd>Path and name of the toolbox configuration file. The path must be
 *     relative to the web application root directory. If this parameter is
 *     not found, the servlet will check for a toolbox file at
 *     '/WEB-INF/toolbox.xml'.</dd>
 *   <dt>org.apache.velocity.properties</dt>
 *   <dd>Path and name of the Velocity configuration file. The path must be
 *     relative to the web application root directory. If this parameter
 *     is not present, Velocity will check for a properties file at
 *     '/WEB-INF/velocity.properties'.  If no file is found there, then
 *     Velocity is initialized with the settings in the classpath at
 *     'org.apache.velocity.tools.view.servlet.velocity.properties'.</dd>
 * </dl>
 *
 * <p>There are methods you may wish to override to access, alter or control
 * any part of the request processing chain.  Please see the javadocs for
 * more information on :
 * <ul>
 * <li> {@link #loadConfiguration} : <br>for loading Velocity properties and
 *                                     configuring the Velocity runtime
 * <li> {@link #setContentType} : <br>for changing the content type on a request
 *                                  by request basis
 * <li> {@link #requestCleanup} : <br>post rendering resource or other cleanup
 * <li> {@link #error} : <br>error handling
 * </ul>
 * </p>
 *
 * @author Dave Bryson
 * @author <a href="mailto:[e-mail]">Jon S. Stevens</a>
 * @author <a href="mailto:[e-mail]">Gabe Sidler</a>
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @author <a href="mailto:[e-mail]">Kent Johnson</a>
 * @author <a href="mailto:[e-mail]">Daniel Rall</a>
 * @author Nathan Bubna
 *
 * @version $Id: VelocityViewServlet.java 488468 2006-12-19 00:19:30Z nbubna $
 */

public class VelocityViewServlet extends HttpServlet
{

    /** serial version id */
    private static final long serialVersionUID = -3329444102562079189L;

    /** The HTTP content type context key. */
    public static final String CONTENT_TYPE = "default.contentType";

    /** The default content type for the response */
    public static final String DEFAULT_CONTENT_TYPE = "text/html";

    /** Default encoding for the output stream */
    public static final String DEFAULT_OUTPUT_ENCODING = "ISO-8859-1";

    /**
     * Key used to access the ServletContext in
     * the Velocity application attributes.
     */
    public static final String SERVLET_CONTEXT_KEY =
        ServletContext.class.getName();

    /**
     * Default Runtime properties.
     */
    public static final String DEFAULT_TOOLS_PROPERTIES =
        "/org/apache/velocity/tools/view/servlet/velocity.properties";


    /**
     * Key used to access the toolbox configuration file path from the
     * Servlet or webapp init parameters ("org.apache.velocity.toolbox").
     */
    protected static final String TOOLBOX_KEY =
        "org.apache.velocity.toolbox";

    /**
     * This is the string that is looked for when getInitParameter is
     * called ("org.apache.velocity.properties").
     */
    protected static final String INIT_PROPS_KEY =
        "org.apache.velocity.properties";

    /**
     * Default toolbox configuration file path. If no alternate value for
     * this is specified, the servlet will look here.
     */
    protected static final String DEFAULT_TOOLBOX_PATH =
        "/WEB-INF/toolbox.xml";

    /**
     * Default velocity properties file path. If no alternate value for
     * this is specified, the servlet will look here.
     */
    protected static final String DEFAULT_PROPERTIES_PATH =
        "/WEB-INF/velocity.properties";

    /** A reference to the toolbox manager. */
    protected ToolboxManager toolboxManager = null;


    /** Cache of writers */
    private static SimplePool writerPool = new SimplePool(40);

    /* The engine used to process templates. */
    private VelocityEngine velocity = null;

    /**
     * The default content type.  When necessary, includes the
     * character set to use when encoding textual output.
     */
    private String defaultContentType;

    /**
     * Whether we've logged a deprecation warning for
     * ServletResponse's <code>getOutputStream()</code>.
     * @since VelocityTools 1.1
     */
    private boolean warnOfOutputStreamDeprecation = true;



    /**
     * <p>Initializes servlet, toolbox and Velocity template engine.
     * Called by the servlet container on loading.</p>
     *
     * <p>NOTE: If no charset is specified in the default.contentType
     * property (in your velocity.properties) and you have specified
     * an output.encoding property, then that will be used as the
     * charset for the default content-type of pages served by this
     * servlet.</p>
     *
     * @param config servlet configuation
     */
    public void init(ServletConfig config) throws ServletException
    {
        super.init(config);

        // do whatever we have to do to init Velocity
        initVelocity(config);

        // init this servlet's toolbox (if any)
        initToolbox(config);

        // we can get these now that velocity is initialized
        defaultContentType =
            (String)getVelocityProperty(CONTENT_TYPE, DEFAULT_CONTENT_TYPE);

        String encoding =
            (String)getVelocityProperty(RuntimeConstants.OUTPUT_ENCODING,
                                        DEFAULT_OUTPUT_ENCODING);

        // For non Latin-1 encodings, ensure that the charset is
        // included in the Content-Type header.
        if (!DEFAULT_OUTPUT_ENCODING.equalsIgnoreCase(encoding))
        {
            int index = defaultContentType.lastIndexOf("charset");
            if (index < 0)
            {
                // the charset specifier is not yet present in header.
                // append character encoding to default content-type
                defaultContentType += "; charset=" + encoding;
            }
            else
            {
                // The user may have configuration issues.
                velocity.warn("VelocityViewServlet: Charset was already " +
                              "specified in the Content-Type property.  " +
                              "Output encoding property will be ignored.");
            }
        }

        velocity.info("VelocityViewServlet: Default content-type is: " +
                      defaultContentType);
    }


    /**
     * Looks up an init parameter with the specified key in either the
     * ServletConfig or, failing that, in the ServletContext.
     */
    protected String findInitParameter(ServletConfig config, String key)
    {
        // check the servlet config
        String param = config.getInitParameter(key);

        if (param == null || param.length() == 0)
        {
            // check the servlet context
            ServletContext servletContext = config.getServletContext();
            param = servletContext.getInitParameter(key);
        }
        return param;
    }


    /**
     * Simplifies process of getting a property from VelocityEngine,
     * because the VelocityEngine interface sucks compared to the singleton's.
     * Use of this method assumes that {@link #initVelocity(ServletConfig)}
     * has already been called.
     */
    protected String getVelocityProperty(String key, String alternate)
    {
        String prop = (String)velocity.getProperty(key);
        if (prop == null || prop.length() == 0)
        {
            return alternate;
        }
        return prop;
    }


    /**
     * Returns the underlying VelocityEngine being used.
     */
    protected VelocityEngine getVelocityEngine()
    {
        return velocity;
    }

    /**
     * Sets the underlying VelocityEngine
     */
    protected void setVelocityEngine(VelocityEngine ve)