webappclassloader.java

业界著名的tomcat服务器的最新6.0的源代码。

/*
 * 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.catalina.loader;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FilePermission;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessControlException;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Policy;
import java.security.PrivilegedAction;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Vector;
import java.util.jar.Attributes;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.Manifest;
import java.util.jar.Attributes.Name;

import javax.naming.NameClassPair;
import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.DirContext;

import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.util.StringManager;
import org.apache.naming.JndiPermission;
import org.apache.naming.resources.Resource;
import org.apache.naming.resources.ResourceAttributes;
import org.apache.tomcat.util.IntrospectionUtils;

/**
 * Specialized web application class loader.
 * <p>
 * This class loader is a full reimplementation of the 
 * <code>URLClassLoader</code> from the JDK. It is desinged to be fully
 * compatible with a normal <code>URLClassLoader</code>, although its internal
 * behavior may be completely different.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - This class loader faithfully follows 
 * the delegation model recommended in the specification. The system class 
 * loader will be queried first, then the local repositories, and only then 
 * delegation to the parent class loader will occur. This allows the web 
 * application to override any shared class except the classes from J2SE.
 * Special handling is provided from the JAXP XML parser interfaces, the JNDI
 * interfaces, and the classes from the servlet API, which are never loaded 
 * from the webapp repository.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - Due to limitations in Jasper 
 * compilation technology, any repository which contains classes from 
 * the servlet API will be ignored by the class loader.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - The class loader generates source
 * URLs which include the full JAR URL when a class is loaded from a JAR file,
 * which allows setting security permission at the class level, even when a
 * class is contained inside a JAR.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - Local repositories are searched in
 * the order they are added via the initial constructor and/or any subsequent
 * calls to <code>addRepository()</code> or <code>addJar()</code>.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - No check for sealing violations or
 * security is made unless a security manager is present.
 *
 * @author Remy Maucherat
 * @author Craig R. McClanahan
 * @version $Revision: 482586 $ $Date: 2006-12-05 11:55:38 +0100 (mar., 05 déc. 2006) $
 */
public class WebappClassLoader
    extends URLClassLoader
    implements Reloader, Lifecycle
 {

    protected static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog( WebappClassLoader.class );

    public static final boolean ENABLE_CLEAR_REFERENCES = 
        Boolean.valueOf(System.getProperty("org.apache.catalina.loader.WebappClassLoader.ENABLE_CLEAR_REFERENCES", "true")).booleanValue();
    
    protected class PrivilegedFindResource
        implements PrivilegedAction {

        protected File file;
        protected String path;

        PrivilegedFindResource(File file, String path) {
            this.file = file;
            this.path = path;
        }

        public Object run() {
            return findResourceInternal(file, path);
        }

    }


    // ------------------------------------------------------- Static Variables


    /**
     * The set of trigger classes that will cause a proposed repository not
     * to be added if this class is visible to the class loader that loaded
     * this factory class.  Typically, trigger classes will be listed for
     * components that have been integrated into the JDK for later versions,
     * but where the corresponding JAR files are required to run on
     * earlier versions.
     */
    protected static final String[] triggers = {
        "javax.servlet.Servlet"                     // Servlet API
    };


    /**
     * Set of package names which are not allowed to be loaded from a webapp
     * class loader without delegating first.
     */
    protected static final String[] packageTriggers = {
    };


    /**
     * The string manager for this package.
     */
    protected static final StringManager sm =
        StringManager.getManager(Constants.Package);

    
    /**
     * Use anti JAR locking code, which does URL rerouting when accessing
     * resources.
     */
    boolean antiJARLocking = false; 
    

    // ----------------------------------------------------------- Constructors


    /**
     * Construct a new ClassLoader with no defined repositories and no
     * parent ClassLoader.
     */
    public WebappClassLoader() {

        super(new URL[0]);
        this.parent = getParent();
        system = getSystemClassLoader();
        securityManager = System.getSecurityManager();

        if (securityManager != null) {
            refreshPolicy();
        }

    }


    /**
     * Construct a new ClassLoader with no defined repositories and no
     * parent ClassLoader.
     */
    public WebappClassLoader(ClassLoader parent) {

        super(new URL[0], parent);
                
        this.parent = getParent();
        
        system = getSystemClassLoader();
        securityManager = System.getSecurityManager();

        if (securityManager != null) {
            refreshPolicy();
        }
    }


    // ----------------------------------------------------- Instance Variables


    /**
     * Associated directory context giving access to the resources in this
     * webapp.
     */
    protected DirContext resources = null;


    /**
     * The cache of ResourceEntry for classes and resources we have loaded,
     * keyed by resource name.
     */
    protected HashMap resourceEntries = new HashMap();


    /**
     * The list of not found resources.
     */
    protected HashMap notFoundResources = new HashMap();


    /**
     * Should this class loader delegate to the parent class loader
     * <strong>before</strong> searching its own repositories (i.e. the
     * usual Java2 delegation model)?  If set to <code>false</code>,
     * this class loader will search its own repositories first, and
     * delegate to the parent only if the class or resource is not
     * found locally.
     */
    protected boolean delegate = false;


    /**
     * Last time a JAR was accessed.
     */
    protected long lastJarAccessed = 0L;


    /**
     * The list of local repositories, in the order they should be searched
     * for locally loaded classes or resources.
     */
    protected String[] repositories = new String[0];


     /**
      * Repositories URLs, used to cache the result of getURLs.
      */
     protected URL[] repositoryURLs = null;


    /**
     * Repositories translated as path in the work directory (for Jasper
     * originally), but which is used to generate fake URLs should getURLs be
     * called.
     */
    protected File[] files = new File[0];


    /**
     * The list of JARs, in the order they should be searched
     * for locally loaded classes or resources.
     */
    protected JarFile[] jarFiles = new JarFile[0];


    /**
     * The list of JARs, in the order they should be searched
     * for locally loaded classes or resources.
     */
    protected File[] jarRealFiles = new File[0];


    /**
     * The path which will be monitored for added Jar files.
     */
    protected String jarPath = null;


    /**
     * The list of JARs, in the order they should be searched
     * for locally loaded classes or resources.
     */
    protected String[] jarNames = new String[0];


    /**
     * The list of JARs last modified dates, in the order they should be
     * searched for locally loaded classes or resources.
     */
    protected long[] lastModifiedDates = new long[0];


    /**
     * The list of resources which should be checked when checking for
     * modifications.
     */
    protected String[] paths = new String[0];


    /**
     * A list of read File and Jndi Permission's required if this loader
     * is for a web application context.
     */
    protected ArrayList permissionList = new ArrayList();


    /**
     * Path where resources loaded from JARs will be extracted.
     */
    protected File loaderDir = null;


    /**
     * The PermissionCollection for each CodeSource for a web
     * application context.
     */
    protected HashMap loaderPC = new HashMap();


    /**
     * Instance of the SecurityManager installed.
     */
    protected SecurityManager securityManager = null;


    /**
     * The parent class loader.
     */
    protected ClassLoader parent = null;


    /**
     * The system class loader.
     */
    protected ClassLoader system = null;


    /**
     * Has this component been started?
     */
    protected boolean started = false;


    /**
     * Has external repositories.
     */
    protected boolean hasExternalRepositories = false;

    /**
     * need conversion for properties files
     */
    protected boolean needConvert = false;


    /**
     * All permission.
     */
    protected Permission allPermission = new java.security.AllPermission();


    // ------------------------------------------------------------- Properties


    /**
     * Get associated resources.
     */
    public DirContext getResources() {

        return this.resources;

    }


    /**
     * Set associated resources.
     */
    public void setResources(DirContext resources) {

        this.resources = resources;