/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package com.sun.naming.internal;

import java.io.InputStream;

import java.io.IOException;

import java.net.URL;

import java.lang.ref.WeakReference;

import java.lang.reflect.Method;

import java.lang.reflect.InvocationTargetException;

import java.util.Enumeration;

import java.util.HashMap;

import java.util.Hashtable;

import java.util.Map;

import java.util.Properties;

import java.util.StringTokenizer;

import java.util.List;

import java.util.ArrayList;

import java.util.WeakHashMap;

import javax.naming.*;

/**

  * The ResourceManager class facilitates the reading of JNDI resource files.

  *

  * @author Rosanna Lee

  * @author Scott Seligman

  */

public final class ResourceManager {

    /*

     * Name of provider resource files (without the package-name prefix.)

     */

    private static final String PROVIDER_RESOURCE_FILE_NAME =

            "jndiprovider.properties";

    /*

     * Name of application resource files.

     */

    private static final String APP_RESOURCE_FILE_NAME = "jndi.properties";

    /*

     * Name of properties file in <java.home>/lib.

     */

    private static final String JRELIB_PROPERTY_FILE_NAME = "jndi.properties";

    /*

     * The standard JNDI properties that specify colon-separated lists.

     */

    private static final String[] listProperties = {

        Context.OBJECT_FACTORIES,

        Context.URL_PKG_PREFIXES,

        Context.STATE_FACTORIES,

        // The following shouldn't create a runtime dependence on ldap package.

        javax.naming.ldap.LdapContext.CONTROL_FACTORIES

    };

    private static final VersionHelper helper =

            VersionHelper.getVersionHelper();

    /*

     * A cache of the properties that have been constructed by

     * the ResourceManager.  A Hashtable from a provider resource

     * file is keyed on a class in the resource file's package.

     * One from application resource files is keyed on the thread's

     * context class loader.

     */

    private static final WeakHashMap propertiesCache = new WeakHashMap(11);

    /*

     * A cache of factory objects (ObjectFactory, StateFactory, ControlFactory).

     *

     * A two-level cache keyed first on context class loader and then

     * on propValue.  Value is a list of class or factory objects,

     * weakly referenced so as not to prevent GC of the class loader.

     * Used in getFactories().

     */

    private static final WeakHashMap factoryCache = new WeakHashMap(11);

    /*

     * A cache of URL factory objects (ObjectFactory).

     *

     * A two-level cache keyed first on context class loader and then

     * on classSuffix+propValue.  Value is the factory itself (weakly

     * referenced so as not to prevent GC of the class loader) or

     * NO_FACTORY if a previous search revealed no factory.  Used in

     * getFactory().

     */

    private static final WeakHashMap urlFactoryCache = new WeakHashMap(11);

    private static final WeakReference NO_FACTORY = new WeakReference(null);

    /**

     * A class to allow JNDI properties be specified as applet parameters

     * without creating a static dependency on java.applet.

     */

    private static class AppletParameter {

        private static final Class<?> clazz = getClass("java.applet.Applet");

        private static final Method getMethod =

            getMethod(clazz, "getParameter", String.class);

        private static Class<?> getClass(String name) {

            try {

                return Class.forName(name, true, null);

            } catch (ClassNotFoundException e) {

                return null;

            }

        }

        private static Method getMethod(Class<?> clazz,

                                        String name,

                                        Class<?>... paramTypes)

        {

            if (clazz != null) {

                try {

                    return clazz.getMethod(name, paramTypes);

                } catch (NoSuchMethodException e) {

                    throw new AssertionError(e);

                }

            } else {

                return null;

            }

        }

        /**

         * Returns the value of the applet's named parameter.

         */

        static Object get(Object applet, String name) {

            // if clazz is null then applet cannot be an Applet.

            if (clazz == null || !clazz.isInstance(applet))

                throw new ClassCastException(applet.getClass().getName());

            try {

                return getMethod.invoke(applet, name);

            } catch (InvocationTargetException e) {

                throw new AssertionError(e);

            } catch (IllegalAccessException iae) {

                throw new AssertionError(iae);

            }

        }

    }

    // There should be no instances of this class.

    private ResourceManager() {

    }

    // ---------- Public methods ----------

    /*

     * Given the environment parameter passed to the initial context

     * constructor, returns the full environment for that initial

     * context (never null).  This is based on the environment

     * parameter, the applet parameters (where appropriate), the

     * system properties, and all application resource files.

     *

     * <p> This method will modify <tt>env</tt> and save

     * a reference to it.  The caller may no longer modify it.

     *

     * @param env       environment passed to initial context constructor.

     *                  Null indicates an empty environment.

     *

     * @throws NamingException if an error occurs while reading a

     *          resource file

     */

    public static Hashtable getInitialEnvironment(Hashtable env)

            throws NamingException

    {

        String[] props = VersionHelper.PROPS;   // system/applet properties

        if (env == null) {

            env = new Hashtable(11);

        }

        Object applet = env.get(Context.APPLET);

        // Merge property values from env param, applet params, and system

        // properties.  The first value wins:  there's no concatenation of

        // colon-separated lists.

        // Read system properties by first trying System.getProperties(),

        // and then trying System.getProperty() if that fails.  The former

        // is more efficient due to fewer permission checks.

        //

        String[] jndiSysProps = helper.getJndiProperties();

        for (int i = 0; i < props.length; i++) {

            Object val = env.get(props[i]);

            if (val == null) {

                if (applet != null) {

                    val = AppletParameter.get(applet, props[i]);

                }

                if (val == null) {

                    // Read system property.

                    val = (jndiSysProps != null)

                        ? jndiSysProps[i]

                        : helper.getJndiProperty(i);

                }

                if (val != null) {

                    env.put(props[i], val);

                }

            }

        }

        // Merge the above with the values read from all application

        // resource files.  Colon-separated lists are concatenated.

        mergeTables(env, getApplicationResources());

        return env;

    }

    /**

      * Retrieves the property from the environment, or from the provider

      * resource file associated with the given context.  The environment

      * may in turn contain values that come from applet parameters,

      * system properties, or application resource files.

      *

      * If <tt>concat</tt> is true and both the environment and the provider

      * resource file contain the property, the two values are concatenated

      * (with a ':' separator).

      *

      * Returns null if no value is found.

      *

      * @param propName The non-null property name

      * @param env      The possibly null environment properties

      * @param ctx      The possibly null context

      * @param concat   True if multiple values should be concatenated

      * @return the property value, or null is there is none.

      * @throws NamingException if an error occurs while reading the provider

      * resource file.

      */

    public static String getProperty(String propName, Hashtable env,

        Context ctx, boolean concat)

            throws NamingException {

        String val1 = (env != null) ? (String)env.get(propName) : null;

        if ((ctx == null) ||

            ((val1 != null) && !concat)) {

            return val1;

        }

        String val2 = (String)getProviderResource(ctx).get(propName);

        if (val1 == null) {

            return val2;

        } else if ((val2 == null) || !concat) {

            return val1;

        } else {

            return (val1 + ":" + val2);

        }

    }

    /**

     * Retrieves an enumeration of factory classes/object specified by a

     * property.

     *

     * The property is gotten from the environment and the provider

     * resource file associated with the given context and concantenated.

     * See getProperty(). The resulting property value is a list of class names.

     *<p>

     * This method then loads each class using the current thread's context

     * class loader and keeps them in a list. Any class that cannot be loaded

     * is ignored. The resulting list is then cached in a two-level

     * hash table, keyed first by the context class loader and then by

     * the property's value.

     * The next time threads of the same context class loader call this

     * method, they can use the cached list.

     *<p>

     * After obtaining the list either from the cache or by creating one from

     * the property value, this method then creates and returns a

     * FactoryEnumeration using the list. As the FactoryEnumeration is

     * traversed, the cached Class object in the list is instantiated and

     * replaced by an instance of the factory object itself.  Both class

     * objects and factories are wrapped in weak references so as not to

     * prevent GC of the class loader.

     *<p>

     * Note that multiple threads can be accessing the same cached list

     * via FactoryEnumeration, which locks the list during each next().

     * The size of the list will not change,

     * but a cached Class object might be replaced by an instantiated factory

     * object.

     *

     * @param propName  The non-null property name

     * @param env       The possibly null environment properties

     * @param ctx       The possibly null context

     * @return An enumeration of factory classes/objects; null if none.

     * @exception NamingException If encounter problem while reading the provider

     * property file.

     * @see javax.naming.spi.NamingManager#getObjectInstance

     * @see javax.naming.spi.NamingManager#getStateToBind

     * @see javax.naming.spi.DirectoryManager#getObjectInstance

     * @see javax.naming.spi.DirectoryManager#getStateToBind

     * @see javax.naming.ldap.ControlFactory#getControlInstance

     */

    public static FactoryEnumeration getFactories(String propName, Hashtable env,

        Context ctx) throws NamingException {

        String facProp = getProperty(propName, env, ctx, true);

        if (facProp == null)

            return null;  // no classes specified; return null

        // Cache is based on context class loader and property val

        ClassLoader loader = helper.getContextClassLoader();

        Map perLoaderCache = null;

        synchronized (factoryCache) {

            perLoaderCache = (Map) factoryCache.get(loader);

            if (perLoaderCache == null) {

                perLoaderCache = new HashMap(11);

                factoryCache.put(loader, perLoaderCache);

            }

        }

        synchronized (perLoaderCache) {

            List factories = (List) perLoaderCache.get(facProp);

            if (factories != null) {

                // Cached list

                return factories.size() == 0 ? null

                    : new FactoryEnumeration(factories, loader);

            } else {

                // Populate list with classes named in facProp; skipping

                // those that we cannot load

                StringTokenizer parser = new StringTokenizer(facProp, ":");

                factories = new ArrayList(5);

                while (parser.hasMoreTokens()) {

                    try {

                        // System.out.println("loading");

                        String className = parser.nextToken();

                        Class c = helper.loadClass(className, loader);

                        factories.add(new NamedWeakReference(c, className));

                    } catch (Exception e) {

                        // ignore ClassNotFoundException, IllegalArgumentException

                    }

                }

                // System.out.println("adding to cache: " + factories);

                perLoaderCache.put(facProp, factories);

                return new FactoryEnumeration(factories, loader);

            }

        }

    }

    /**

     * Retrieves a factory from a list of packages specified in a

     * property.

     *

     * The property is gotten from the environment and the provider

     * resource file associated with the given context and concatenated.

     * classSuffix is added to the end of this list.

     * See getProperty(). The resulting property value is a list of package

     * prefixes.

     *<p>

     * This method then constructs a list of class names by concatenating

     * each package prefix with classSuffix and attempts to load and

     * instantiate the class until one succeeds.

     * Any class that cannot be loaded is ignored.

     * The resulting object is then cached in a two-level hash table,

     * keyed first by the context class loader and then by the property's

     * value and classSuffix.

     * The next time threads of the same context class loader call this

     * method, they use the cached factory.

     * If no factory can be loaded, NO_FACTORY is recorded in the table

     * so that next time it'll return quickly.

     *

     * @param propName  The non-null property name

     * @param env       The possibly null environment properties

     * @param ctx       The possibly null context

     * @param classSuffix The non-null class name

     *                  (e.g. ".ldap.ldapURLContextFactory).

     * @param defaultPkgPrefix The non-null default package prefix.

     *        (e.g., "com.sun.jndi.url").

     * @return An factory object; null if none.

     * @exception NamingException If encounter problem while reading the provider

     * property file, or problem instantiating the factory.

     *

     * @see javax.naming.spi.NamingManager#getURLContext

     * @see javax.naming.spi.NamingManager#getURLObject

     */

    public static Object getFactory(String propName, Hashtable env, Context ctx,

        String classSuffix, String defaultPkgPrefix) throws NamingException {

        // Merge property with provider property and supplied default

        String facProp = getProperty(propName, env, ctx, true);

        if (facProp != null)

            facProp += (":" + defaultPkgPrefix);

        else

            facProp = defaultPkgPrefix;

        // Cache factory based on context class loader, class name, and

        // property val

        ClassLoader loader = helper.getContextClassLoader();

        String key = classSuffix + " " + facProp;

        Map perLoaderCache = null;

        synchronized (urlFactoryCache) {

            perLoaderCache = (Map) urlFactoryCache.get(loader);

            if (perLoaderCache == null) {

                perLoaderCache = new HashMap(11);

                urlFactoryCache.put(loader, perLoaderCache);

            }

        }

        synchronized (perLoaderCache) {

            Object factory = null;

            WeakReference factoryRef = (WeakReference) perLoaderCache.get(key);

            if (factoryRef == NO_FACTORY) {

                return null;

            } else if (factoryRef != null) {

                factory = factoryRef.get();

                if (factory != null) {  // check if weak ref has been cleared

                    return factory;

                }

            }

            // Not cached; find first factory and cache

            StringTokenizer parser = new StringTokenizer(facProp, ":");

            String className;

            while (factory == null && parser.hasMoreTokens()) {

                className = parser.nextToken() + classSuffix;

                try {

                    // System.out.println("loading " + className);

                    factory = helper.loadClass(className, loader).newInstance();

                } catch (InstantiationException e) {

                    NamingException ne =

                        new NamingException("Cannot instantiate " + className);

                    ne.setRootCause(e);

                    throw ne;

                } catch (IllegalAccessException e) {

                    NamingException ne =

                        new NamingException("Cannot access " + className);

                    ne.setRootCause(e);

                    throw ne;

                } catch (Exception e) {

                    // ignore ClassNotFoundException, IllegalArgumentException,

                    // etc.

                }

            }

            // Cache it.

            perLoaderCache.put(key, (factory != null)

                                        ? new WeakReference(factory)

                                        : NO_FACTORY);

            return factory;

        }

    }

    // ---------- Private methods ----------

    /*

     * Returns the properties contained in the provider resource file

     * of an object's package.  Returns an empty hash table if the

     * object is null or the resource file cannot be found.  The

     * results are cached.

     *

     * @throws NamingException if an error occurs while reading the file.

     */

    private static Hashtable getProviderResource(Object obj)

            throws NamingException

    {

        if (obj == null) {

            return (new Hashtable(1));

        }

        synchronized (propertiesCache) {

            Class c = obj.getClass();

            Hashtable props = (Hashtable)propertiesCache.get(c);

            if (props != null) {

                return props;

            }

            props = new Properties();

            InputStream istream =

                helper.getResourceAsStream(c, PROVIDER_RESOURCE_FILE_NAME);

            if (istream != null) {

                try {

                    ((Properties)props).load(istream);

                } catch (IOException e) {

                    NamingException ne = new ConfigurationException(

                            "Error reading provider resource file for " + c);

                    ne.setRootCause(e);

                    throw ne;

                }

            }

            propertiesCache.put(c, props);

            return props;

        }

    }

    /*

     * Returns the Hashtable (never null) that results from merging

     * all application resource files available to this thread's

     * context class loader.  The properties file in <java.home>/lib

     * is also merged in.  The results are cached.

     *

     * SECURITY NOTES:

     * 1.  JNDI needs permission to read the application resource files.

     * 2.  Any class will be able to use JNDI to view the contents of

     * the application resource files in its own classpath.  Give

     * careful consideration to this before storing sensitive

     * information there.

     *

     * @throws NamingException if an error occurs while reading a resource

     *  file.

     */

    private static Hashtable getApplicationResources() throws NamingException {

        ClassLoader cl = helper.getContextClassLoader();