/* * ModuleLoader - A generic, policy-driven class loader. * Copyright (c) 2004, Richard S. Hall * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * *   * Redistributions of source code must retain the above copyright *     notice, this list of conditions and the following disclaimer. *   * Redistributions in binary form must reproduce the above copyright *     notice, this list of conditions and the following disclaimer in *     the documentation and/or other materials provided with the *     distribution. *   * Neither the name of the ungoverned.org nor the names of its *     contributors may be used to endorse or promote products derived *     from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * Contact: Richard S. Hall (heavy@ungoverned.org) * Contributor(s): ***/package org.ungoverned.moduleloader;import java.util.*;/** * <p> * The <tt>ModuleManager</tt> class is the core facility for defining a * re-usable, policy-driven class loader for applications that require * flexible class loading mechanisms. The <tt>ModuleManager</tt> is not * class loader itself, but it supports the concept of a * <a href="Module.html"><tt>Module</tt></a>, * which is a unit of organization for application classes and resources. * The <tt>ModuleManager</tt> has only a handful of methods that allow * an application to add, remove, reset, and query modules; the intent * is to place as few assumptions in the <tt>ModuleManager</tt> as possible. * </p> * <p> * The idea is simple, allow the application to map itself into modules * however it sees fit and let the <tt>ModuleManager</tt> assume the * responsibility of managing the modules and loading classes and resources * from them as necessary via <a href="ModuleClassLoader.html"><tt>ModuleClassLoader</tt></a>s * that are associated with each module. In order to achieve this goal, though, the * <tt>ModuleManager</tt> must make at least one assumption on behalf of * the application. This assumption is that the loading of classes and resources * from the available modules must happen using a search algorithm * that is particular to the application itself. As a result of this assumption, * the <tt>ModuleManager</tt> requires that the application provide a concrete * implementation of the <a href="SearchPolicy.html"><tt>SearchPolicy</tt></a> * interface. * </p> * <p> * The search policy allows the <tt>ModuleLoader</tt> to let applications inject * their own particular class loading policies, without dictating strict or * constraining base assumptions. Of course, it is likely that many applications * will use the same or very similar search policies. Because of this, another * goal of the <tt>ModuleLoader</tt> approach is to foster a common library of * search policies that applications are free to use or customize as they see * fit. These common search policies are analagous to patterns, where each search * policy is viewable as a <i>class loading pattern</i>. Some initial search * policies included with the <tt>ModuleLoader</tt> are * <a href="search/ExhaustiveSearchPolicy.html"><tt>ExhaustiveSearchPolicy</tt></a>, * <a href="search/SelfContainedSearchPolicy.html"><tt>SelfContainedSearchPolicy</tt></a>, and * <a href="search/ImportSearchPolicy.html"><tt>ImportSearchPolicy</tt></a>. * </p> * <p> * Due to the fact that class loaders are tied to security and resource loading, * the search policy alone is not sufficient for the <tt>ModuleLoader</tt> to * perform its function. To fulfill these other purposes, the <tt>ModuleLoader</tt> * introduces another policy interface, called the <a href="URLPolicy.html"><tt>URLPolicy</tt></a>. * The <tt>URLPolicy</tt> allows the application to inject its particular policy * for to purposes: * </p> * <ol> *   <li>Creating the <tt>URL</tt> associated with loading a resource, such as *       the <tt>URL</tt> returned from a call to <tt>Class.getResource()</tt>. *   </li> *   <li>Creating the <tt>URL</tt> that will be associated with a class's *       <tt>CodeSource</tt> when defining the class for purposes of security *       and assigning permissions. *   </li> * </ol> * <p> * The <tt>ModuleLoader</tt> defines a default <tt>URLPolicy</tt>, called * <a href="DefaultURLPolicy.html"><tt>DefaultURLPolicy</tt></a>, that provides * a simple <tt>URLStreamHandler</tt> for accessing resources inside of modules * and that returns <tt>null</tt> for the <tt>CodeSource</tt> <tt>URL</tt>. * Applications only need to supply their own <tt>URLPolicy</tt> if the default * one does not provide the appropriate behavior. * </p> * <p> * It is possible for an application to create multiple instances of the * <tt>ModuleManager</tt> within a single JVM, but it is not possible to * share modules across multiple <tt>ModuleManager</tt>s. A given <tt>ModuleManager</tt> * can only have one <tt>SelectionPolicy</tt> and one <tt>URLPolicy</tt>. * </p> * @see org.ungoverned.moduleloader.Module * @see org.ungoverned.moduleloader.ModuleClassLoader * @see org.ungoverned.moduleloader.SearchPolicy * @see org.ungoverned.moduleloader.URLPolicy * @see org.ungoverned.moduleloader.DefaultURLPolicy**/public class ModuleManager{    private List m_moduleList = new ArrayList();    private Map m_moduleMap = new HashMap();    private SearchPolicy m_searchPolicy = null;    private URLPolicy m_urlPolicy = null;    private ModuleListener[] m_listeners = null;    private static final ModuleListener[] m_noListeners = new ModuleListener[0];    /**     * <p>     * Constructs a <tt>ModuleManager</tt> instance using the specified     * search policy and the default <tt>URL</tt> policy.     * </p>     * @param searchPolicy the search policy that the instance should use.     * @see org.ungoverned.moduleloader.SearchPolicy    **/    public ModuleManager(SearchPolicy searchPolicy)    {        this(searchPolicy, null);    }    /**     * <p>     * Constructs a <tt>ModuleManager</tt> instance using the specified     * search policy and the specified <tt>URL</tt> policy.     * </p>     * @param searchPolicy the search policy that the instance should use.     * @param urlPolicy the <tt>URL</tt> policy that the instance should use.     * @see org.ungoverned.moduleloader.SearchPolicy     * @see org.ungoverned.moduleloader.URLPolicy    **/    public ModuleManager(SearchPolicy searchPolicy, URLPolicy urlPolicy)    {        m_listeners = m_noListeners;        m_searchPolicy = searchPolicy;        m_searchPolicy.setModuleManager(this);        if (urlPolicy == null)        {            m_urlPolicy = new DefaultURLPolicy();        }        else        {            m_urlPolicy = urlPolicy;        }    }    /**     * <p>     * Returns the <tt>URL</tt> policy used by this instance.     * </p>     * @return the <tt>URL</tt> policy used by this instance.     * @see org.ungoverned.moduleloader.URLPolicy    **/    public URLPolicy getURLPolicy()    {        return m_urlPolicy;    }    /**     * <p>     * Returns the search policy used by this instance.     * </p>     * @return the search policy used by this instance.     * @see org.ungoverned.moduleloader.SearchPolicy    **/    public SearchPolicy getSearchPolicy()    {        return m_searchPolicy;    }    /**     * <p>     * Returns an array of all modules being managed by the     * <tt>ModuleManager</tt> instance. The array contains a snapshot of     * all modules in the <tt>ModuleManager</tt> at the time when this     * method was called.     * </p>     * @return an array of all modules being managed by the <tt>ModuleManager</tt>     *         instance.     * @see org.ungoverned.moduleloader.Module    **/    public synchronized Module[] getModules()    {        Module[] modules = new Module[m_moduleList.size()];        return (Module[]) m_moduleList.toArray(modules);    }    /**     * <p>     * Returns a module associated with the specified identifier.     * </p>     * @param id the identifier for the module to be retrieved.     * @return the module associated with the identifier or <tt>null</tt>.     * @see org.ungoverned.moduleloader.Module    **/    public synchronized Module getModule(String id)    {        return (Module) m_moduleMap.get(id);    }    /**     * <p>     * Adds a module to the module manager. The module will have the specified     * unique identifier, with the associated attributes, resource sources, and     * library sources. If the identifier is not unique, then an exception is     * thrown.     * </p>     * @param id the unique identifier of the new module.     * @param attributes an array of key-value attribute pairs to     *        associate with the module.     * @param resSources an array of <tt>ResourceSource</tt>s to associate     *        with the module.     * @param libSources an array of <tt>LibrarySource</tt>s to associate     *        with the module.     * @return the newly created module.     * @throws java.lang.IllegalArgumentException if the module identifier     *         is not unique.     * @see org.ungoverned.moduleloader.Module     * @see org.ungoverned.moduleloader.ResourceSource     * @see org.ungoverned.moduleloader.LibrarySource    **/    public Module addModule(String id, Object[][] attributes,        ResourceSource[] resSources, LibrarySource[] libSources)    {        Module module = null;        // Use a synchronized block instead of synchronizing the        // method, so we can fire our event outside of the block.        synchronized (this)        {            if (m_moduleMap.get(id) == null)            {                module = new Module(this, id, attributes, resSources, libSources);                m_moduleList.add(module);                m_moduleMap.put(id, module);            }            else            {                throw new IllegalArgumentException("Module ID must be unique.");            }        }        // Fire event here instead of inside synchronized block.        fireModuleAdded(module);        return module;    }    /**     * <p>