digestingplugin.java

structs源码

/*
 * $Id: DigestingPlugIn.java 471754 2006-11-06 14:55:09Z husted $
 *
 * 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.
 */
package org.apache.struts.plugins;

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.RuleSet;
import org.apache.commons.digester.xmlrules.DigesterLoader;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.PlugIn;
import org.apache.struts.config.ModuleConfig;
import org.apache.struts.util.RequestUtils;
import org.xml.sax.SAXException;

import javax.servlet.ServletException;

import java.io.File;
import java.io.IOException;

import java.net.URL;
import java.net.URLConnection;

/**
 * <p>An implementation of <code>PlugIn</code> which can be configured to
 * instantiate a graph of objects using the Commons Digester and place the
 * root object of that graph into the Application context.</p>
 *
 * @version $Rev: 471754 $
 * @see org.apache.struts.action.PlugIn
 * @since Struts 1.2
 */
public class DigestingPlugIn implements PlugIn {
    /**
     * Commons Logging instance.
     */
    private static Log log = LogFactory.getLog(DigestingPlugIn.class);
    protected static final String SOURCE_CLASSPATH = "classpath";
    protected static final String SOURCE_FILE = "file";
    protected static final String SOURCE_SERVLET = "servlet";
    protected String configPath = null;
    protected String configSource = SOURCE_SERVLET;
    protected String digesterPath = null;
    protected String digesterSource = SOURCE_SERVLET;
    protected String key = null;
    protected ModuleConfig moduleConfig = null;
    protected String rulesets = null;
    protected ActionServlet servlet = null;
    protected boolean push = false;

    /**
     * Constructor for DigestingPlugIn.
     */
    public DigestingPlugIn() {
        super();
    }

    /**
     * Receive notification that our owning module is being shut down.
     */
    public void destroy() {
        this.servlet = null;
        this.moduleConfig = null;
    }

    /**
     * <p>Initialize a <code>Digester</code> and use it to parse a
     * configuration file, resulting in a root object which will be placed
     * into the ServletContext.</p>
     *
     * @param servlet ActionServlet that is managing all the modules in this
     *                web application
     * @param config  ModuleConfig for the module with which this plug-in is
     *                associated
     * @throws ServletException if this <code>PlugIn</code> cannot be
     *                          successfully initialized
     */
    public void init(ActionServlet servlet, ModuleConfig config)
        throws ServletException {
        this.servlet = servlet;
        this.moduleConfig = config;

        Object obj = null;

        Digester digester = this.initializeDigester();

        if (this.push) {
            log.debug("push == true; pushing plugin onto digester stack");
            digester.push(this);
        }

        try {
            log.debug("XML data file: [path: " + this.configPath + ", source: "
                + this.configSource + "]");

            URL configURL =
                this.getConfigURL(this.configPath, this.configSource);

            if (configURL == null) {
                throw new ServletException(
                    "Unable to locate XML data file at [path: "
                    + this.configPath + ", source: " + this.configSource + "]");
            }

            URLConnection conn = configURL.openConnection();

            conn.setUseCaches(false);
            conn.connect();
            obj = digester.parse(conn.getInputStream());
        } catch (IOException e) {
            // TODO Internationalize msg
            log.error("Exception processing config", e);
            throw new ServletException(e);
        } catch (SAXException e) {
            // TODO Internationalize msg
            log.error("Exception processing config", e);
            throw new ServletException(e);
        }

        this.storeGeneratedObject(obj);
    }

    /**
     * Initialize the <code>Digester</code> which will be used to process the
     * main configuration.
     *
     * @return a Digester, ready to use.
     * @throws ServletException
     */
    protected Digester initializeDigester()
        throws ServletException {
        Digester digester = null;

        if ((this.digesterPath != null) && (this.digesterSource != null)) {
            try {
                log.debug("Initialize digester from XML [path: "
                    + this.digesterPath + "; source: " + this.digesterSource
                    + "]");
                digester =
                    this.digesterFromXml(this.digesterPath, this.digesterSource);
            } catch (IOException e) {
                // TODO Internationalize msg
                log.error("Exception instantiating digester from XML ", e);
                throw new ServletException(e);
            }
        } else {
            log.debug("No XML rules for digester; call newDigesterInstance()");
            digester = this.newDigesterInstance();
        }

        this.applyRuleSets(digester);

        return digester;
    }

    /**
     * <p>Instantiate a <code>Digester</code>.</p> <p>Subclasses may wish to
     * override this to provide a subclass of Digester, or to configure the
     * Digester using object methods.</p>
     *
     * @return a basic instance of <code>org.apache.commons.digester.Digester</code>
     */
    protected Digester newDigesterInstance() {
        return new Digester();
    }

    /**
     * <p>Instantiate a Digester from an XML input stream using the Commons
     * <code>DigesterLoader</code>.</p>
     *
     * @param path   the path to the digester rules XML to be found using
     *               <code>source</code>
     * @param source a string indicating the lookup method to be used with
     *               <code>path</code>
     * @return a configured Digester
     * @throws FileNotFoundException
     * @throws MalformedURLException
     * @see #getConfigURL(String, String)
     */
    protected Digester digesterFromXml(String path, String source)
        throws IOException {
        URL configURL = this.getConfigURL(path, source);

        if (configURL == null) {
            throw new NullPointerException("No resource '" + path
                + "' found in '" + source + "'");
        }

        return DigesterLoader.createDigester(configURL);
    }

    /**
     * Instantiate any <code>RuleSet</code> classes defined in the
     * <code>rulesets</code> property and use them to add rules to our
     * <code>Digester</code>.
     *
     * @param digester the Digester instance to add RuleSet objects to.
     * @throws ServletException
     */
    protected void applyRuleSets(Digester digester)
        throws ServletException {
        if ((this.rulesets == null) || (this.rulesets.trim().length() == 0)) {
            return;
        }

        rulesets = rulesets.trim();

        String ruleSet = null;

        while (rulesets.length() > 0) {
            int comma = rulesets.indexOf(",");

            if (comma < 0) {
                ruleSet = rulesets.trim();
                rulesets = "";
            } else {
                ruleSet = rulesets.substring(0, comma).trim();
                rulesets = rulesets.substring(comma + 1).trim();
            }

            if (log.isDebugEnabled()) {
                // TODO Internationalize msg
                log.debug("Configuring custom Digester Ruleset of type "
                    + ruleSet);
            }