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Tomcat example source code file (VirtualDirContext.java)

This example Tomcat source code file (VirtualDirContext.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

arraylist, file, file, hashtable, io, list, map, naming, namingexception, override, override, string, string, stringtokenizer, stringtokenizer, util, web-inf

The Tomcat VirtualDirContext.java source code

/*
 * 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.naming.resources;

import java.io.File;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;

import javax.naming.NamingException;
import javax.naming.directory.Attributes;

import org.apache.naming.NamingEntry;

/**
 * Extended FileDirContext implementation that will allow loading of tld files
 * from the META-INF directory (or subdirectories) in classpath. This will fully
 * mimic the behavior of compressed jars also when using unjarred resources. Tld
 * files can be loaded indifferently from WEB-INF webapp dir (or subdirs) or
 * from META-INF dir from jars available in the classpath: using this DirContext
 * implementation you will be able to use unexpanded jars during development and
 * to make any tld in them virtually available to the webapp.
 *
 * Sample context xml configuration:
 *
 * <code>
 * <Context docBase="\webapps\mydocbase">
 *   <Resources className="org.apache.naming.resources.VirtualDirContext"
 *              virtualClasspath="\dir\classes;\somedir\somejar.jar"/>
 * </Resources>
 * </code>
 *
 *
 * <strong>This is not meant to be used for production.
 * Its meant to ease development with IDE's without the
 * need for fully republishing jars in WEB-INF/lib</strong>
 *
 *
 * @author Fabrizio Giustina
 * @version $Id: $
 */
public class VirtualDirContext extends FileDirContext {

    /**
     * Map containing generated virtual names for tld files under WEB-INF and
     * the actual file reference.
     */
    private Map<String, File> virtualMappings;

    /**
     * Map containing a mapping for tag files that should be loaded from the
     * META-INF dir of referenced jar files.
     */
    private Map<String, File> tagfileMappings;

    /**
     * <code>; separated list of virtual path elements.
     */
    private String virtualClasspath;

    /**
     * <code>virtualClasspath attribute that will be automatically set
     * from the <code>Context virtualClasspath attribute
     * from the context xml file.
     * @param path <code>; separated list of path elements.
     */
    public void setVirtualClasspath(String path) {
        virtualClasspath = path;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void allocate() {
        super.allocate();

        virtualMappings = new Hashtable<String, File>();
        tagfileMappings = new Hashtable<String, File>();

        // looks into any META-INF dir found in classpath entries for tld files.
        StringTokenizer tkn = new StringTokenizer(virtualClasspath, ";");
        while (tkn.hasMoreTokens()) {
            File file = new File(tkn.nextToken(), "META-INF");

            if (!file.exists() || !file.isDirectory()) {
                continue;
            }
            scanForTlds(file);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void release() {
        super.release();
        virtualMappings = null;
    }

    @Override
    public Attributes getAttributes(String name) throws NamingException {

        // handle "virtual" tlds
        if (name.startsWith("/WEB-INF/") && name.endsWith(".tld")) {
            String tldName = name.substring(name.lastIndexOf("/") + 1);
            if (virtualMappings.containsKey(tldName)) {
                return new FileResourceAttributes(virtualMappings.get(tldName));
            }
        } else if (name.startsWith("/META-INF/tags") && name.endsWith(".tag")
                || name.endsWith(".tagx")) {

            // already loaded tag file
            if (tagfileMappings.containsKey(name)) {
                return new FileResourceAttributes(tagfileMappings.get(name));
            }

            // unknown tagfile, search for it in virtualClasspath
            StringTokenizer tkn = new StringTokenizer(virtualClasspath, ";");
            while (tkn.hasMoreTokens()) {
                File file = new File(tkn.nextToken(), name);
                if (file.exists()) {
                    tagfileMappings.put(name, file);
                    return new FileResourceAttributes(file);
                }
            }
        }

        return super.getAttributes(name);
    }

    @Override
    @SuppressWarnings("unchecked")
    protected ArrayList list(File file) {
        ArrayList entries = super.list(file);

        // adds virtual tlds for WEB-INF listing
        if ("WEB-INF".equals(file.getName())) {
            entries.addAll(getVirtualNamingEntries());
        }

        return entries;
    }

    @Override
    public Object lookup(String name) throws NamingException {

        // handle "virtual" tlds
        if (name.startsWith("/WEB-INF/") && name.endsWith(".tld")) {
            String tldName = name.substring(name.lastIndexOf("/") + 1);
            if (virtualMappings.containsKey(tldName)) {
                return new FileResource(virtualMappings.get(tldName));
            }
        } else if (name.startsWith("/META-INF/tags") && name.endsWith(".tag")
                || name.endsWith(".tagx")) {

            // already loaded tag file: we are sure that getAttributes() has
            // already been called if we are here
            File tagFile = tagfileMappings.get(name);
            if (tagFile != null) {
                return new FileResource(tagFile);
            }
        }

        return super.lookup(name);
    }

    /**
     * Scan a given dir for tld files. Any found tld will be added to the
     * virtualMappings.
     * @param dir Dir to scan for tlds
     */
    private void scanForTlds(File dir) {

        File[] files = dir.listFiles();
        for (int j = 0; j < files.length; j++) {
            File file = files[j];

            if (file.isDirectory()) {
                scanForTlds(file);
            } else if (file.getName().endsWith(".tld")) {
                // just generate a random name using the current timestamp, name
                // doesn't matter since it needs to be referenced by URI
                String virtualTldName = "~" + System.currentTimeMillis() + "~"
                        + file.getName();
                virtualMappings.put(virtualTldName, file);
            }
        }

    }

    /**
     * Returns a list of virtual naming entries.
     * @return list of naming entries, containing tlds in virtualMappings
     */
    private List<NamingEntry> getVirtualNamingEntries() {
        List<NamingEntry> virtual = new ArrayList();

        for (String name : virtualMappings.keySet()) {

            File file = virtualMappings.get(name);
            NamingEntry entry = new NamingEntry(name, new FileResource(file),
                    NamingEntry.ENTRY);
            virtual.add(entry);
        }
        return virtual;
    }

}

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