xmltoolboxmanager.java

一个用于java web页面开发的开源包

package org.apache.velocity.tools.view;

/*
 * 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.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.RuleSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


/**
 * A ToolboxManager for loading a toolbox from xml.
 *
 * <p>A toolbox manager is responsible for automatically filling the Velocity
 * context with a set of view tools. This class provides the following
 * features:</p>
 * <ul>
 *   <li>configurable through an XML-based configuration file</li>
 *   <li>assembles a set of view tools (the toolbox) on request</li>
 *   <li>supports any class with a public constructor without parameters
 *     to be used as a view tool</li>
 *   <li>supports adding primitive data values to the context(String,Number,Boolean)</li>
 * </ul>
 *
 *
 * <p><strong>Configuration</strong></p>
 * <p>The toolbox manager is configured through an XML-based configuration
 * file. The configuration file is passed to the {@link #load(java.io.InputStream input)}
 * method. The format is shown in the following example:</p>
 * <pre>
 * &lt;?xml version="1.0"?&gt;
 * &lt;toolbox&gt;
 *   &lt;tool&gt;
 *      &lt;key&gt;date&lt;/key&gt;
 *      &lt;class&gt;org.apache.velocity.tools.generic.DateTool&lt;/class&gt;
 *   &lt;/tool&gt;
 *   &lt;data type="Number"&gt;
 *      &lt;key&gt;luckynumber&lt;/key&gt;
 *      &lt;value&gt;1.37&lt;/value&gt;
 *   &lt;/data&gt;
 *   &lt;data type="String"&gt;
 *      &lt;key&gt;greeting&lt;/key&gt;
 *      &lt;value&gt;Hello World!&lt;/value&gt;
 *   &lt;/data&gt;
 * &lt;/toolbox&gt;
 * </pre>
 *
 *
 * @author Nathan Bubna
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @author <a href="mailto:[e-mail]">Henning P. Schmiedehausen</a>
 * @version $Id: XMLToolboxManager.java 479724 2006-11-27 18:49:37Z nbubna $
 */
public class XMLToolboxManager implements ToolboxManager
{
    protected static final Log LOG = LogFactory.getLog(XMLToolboxManager.class);

    private List toolinfo;
    private Map data;

    private static RuleSet ruleSet = new ToolboxRuleSet();


    /**
     * Default constructor
     */
    public XMLToolboxManager()
    {
        toolinfo = new ArrayList();
        data = new HashMap();
    }


    // ------------------------------- ToolboxManager interface ------------


    public void addTool(ToolInfo info)
    {
        System.out.println("addTool("+info);
        if (validateToolInfo(info))
        {
            toolinfo.add(info);
            if (LOG.isDebugEnabled())
            {
                LOG.debug("Added "+info.getClassname()+" to the toolbox as "+info.getKey());
            }
        }
    }

    public void addData(ToolInfo info)
    {
        if (validateToolInfo(info))
        {
            data.put(info.getKey(), info.getInstance(null));
            if (LOG.isDebugEnabled())
            {
                LOG.debug("Added '"+info.getInstance(null)+"' to the toolbox as "+info.getKey());
            }
        }
    }

    /**
     * Checks whether an object described by a ToolInfo passes
     * some basic sanity checks.
     *
     * @param info A ToolInfo object
     *
     * @return true if the ToolInfo is valid
     */
    protected boolean validateToolInfo(ToolInfo info)
    {
        if (info == null)
        {
            LOG.error("ToolInfo is null!");
            return false;
        }
        if (info.getKey() == null || info.getKey().length() == 0)
        {
            LOG.error("Tool has no key defined!");
            return false;
        }
        if (info.getClassname() == null)
        {
            LOG.error("Tool " + info.getKey() + " has no Class definition!");
            return false;
        }
        return true;
    }


    public Map getToolbox(Object initData)
    {
        Map toolbox = new HashMap(data);
        Iterator i = toolinfo.iterator();
        while(i.hasNext())
        {
            ToolInfo info = (ToolInfo)i.next();
            toolbox.put(info.getKey(), info.getInstance(initData));
        }
        return toolbox;
    }


    // ------------------------------- toolbox loading methods ------------

    /**
     * <p>Reads an XML document from the specified file path
     * and sets up the toolbox from that. If the file does not
     * exist, an {@link IllegalArgumentException} will be thrown.</p>
     *
     * @param path the path to the file to be read from
     * @since VelocityTools 1.3
     */
    public void load(String path) throws Exception
    {
        if (path == null)
        {
            throw new IllegalArgumentException("Path value cannot be null");
        }

        File file = new File(path);
        if (!file.exists())
        {
            throw new IllegalArgumentException("Could not find toolbox config file at: "+path);
        }

        // ok, load the file
        load(new FileInputStream(file));
    }

    /**
     * <p>Reads an XML document from an {@link InputStream}
     * and sets up the toolbox from that.</p>
     *
     * @param input the InputStream to read from
     */
    public void load(InputStream input) throws Exception
    {
        LOG.trace("Loading toolbox...");

        Digester digester = new Digester();
        digester.setValidating(false);
        digester.setUseContextClassLoader(true);
        digester.push(this);
        digester.addRuleSet(getRuleSet());
        digester.parse(input);

        LOG.trace("Toolbox loaded.");
    }


    /**
     * <p>Retrieves the rule set Digester should use to parse and load
     * the toolbox for this manager.</p>
     *
     * <p>The DTD corresponding to the default ToolboxRuleSet is:
     * <pre>
     *  &lt;?xml version="1.0"?&gt;
     *  &lt;!ELEMENT toolbox (tool*,data*,#PCDATA)&gt;
     *  &lt;!ELEMENT tool    (key,class,parameter*,#PCDATA)&gt;
     *  &lt;!ELEMENT data    (key,value)&gt;
     *      &lt;!ATTLIST data type (string|number|boolean) "string"&gt;
     *  &lt;!ELEMENT key     (#CDATA)&gt;
     *  &lt;!ELEMENT class   (#CDATA)&gt;
     *  &lt;!ELEMENT parameter (EMPTY)&gt;
     *      &lt;!ATTLIST parameter name CDATA #REQUIRED&gt;
     *      &lt;!ATTLIST parameter value CDATA #REQUIRED&gt;
     *  &lt;!ELEMENT value   (#CDATA)&gt;
     * </pre></p>
     *
     * @since VelocityTools 1.1
     */
    protected RuleSet getRuleSet()
    {
        return ruleSet;
    }

}