1 /*

     2  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Oracle designates this

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

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package javax.naming.ldap;

    27 

    28 import javax.naming.NamingException;

    29 import javax.naming.Context;

    30 

    31 import java.util.Hashtable;

    32 

    33 import com.sun.naming.internal.FactoryEnumeration;

    34 import com.sun.naming.internal.ResourceManager;

    35 

    36 

    37 /**

    38   * This abstract class represents a factory for creating LDAPv3 controls.

    39   * LDAPv3 controls are defined in

    40   * <A HREF="http://www.ietf.org/rfc/rfc2251.txt">RFC 2251</A>.

    41   *<p>

    42   * When a service provider receives a response control, it uses control

    43   * factories to return the specific/appropriate control class implementation.

    44   *

    45   * @author Rosanna Lee

    46   * @author Scott Seligman

    47   * @author Vincent Ryan

    48   *

    49   * @see Control

    50   * @since 1.3

    51   */

    52 

    53 public abstract class ControlFactory {

    54     /**

    55      * Creates a new instance of a control factory.

    56      */

    57     protected ControlFactory() {

    58     }

    59 

    60     /**

    61       * Creates a control using this control factory.

    62       *<p>

    63       * The factory is used by the service provider to return controls

    64       * that it reads from the LDAP protocol as specialized control classes.

    65       * Without this mechanism, the provider would be returning

    66       * controls that only contained data in BER encoded format.

    67       *<p>

    68       * Typically, {@code ctl} is a "basic" control containing

    69       * BER encoded data. The factory is used to create a specialized

    70       * control implementation, usually by decoding the BER encoded data,

    71       * that provides methods to access that data in a type-safe and friendly

    72       * manner.

    73       * <p>

    74       * For example, a factory might use the BER encoded data in

    75       * basic control and return an instance of a VirtualListReplyControl.

    76       *<p>

    77       * If this factory cannot create a control using the argument supplied,

    78       * it should return null.

    79       * A factory should only throw an exception if it is sure that

    80       * it is the only intended factory and that no other control factories

    81       * should be tried. This might happen, for example, if the BER data

    82       * in the control does not match what is expected of a control with

    83       * the given OID. Since this method throws {@code NamingException},

    84       * any other internally generated exception that should be propagated

    85       * must be wrapped inside a {@code NamingException}.

    86       *

    87       * @param ctl A non-null control.

    88       *

    89       * @return A possibly null Control.

    90       * @exception NamingException If {@code ctl} contains invalid data that prevents it

    91       * from being used to create a control. A factory should only throw

    92       * an exception if it knows how to produce the control (identified by the OID)

    93       * but is unable to because of, for example invalid BER data.

    94       */

    95     public abstract Control getControlInstance(Control ctl) throws NamingException;

    96 

    97     /**

    98       * Creates a control using known control factories.

    99       * <p>

   100       * The following rule is used to create the control:

   101       *<ul>

   102       * <li> Use the control factories specified in

   103       *    the {@code LdapContext.CONTROL_FACTORIES} property of the

   104       *    environment, and of the provider resource file associated with

   105       *    {@code ctx}, in that order.

   106       *    The value of this property is a colon-separated list of factory

   107       *    class names that are tried in order, and the first one that succeeds

   108       *    in creating the control is the one used.

   109       *    If none of the factories can be loaded,

   110       *    return {@code ctl}.

   111       *    If an exception is encountered while creating the control, the

   112       *    exception is passed up to the caller.

   113       *</ul>

   114       * <p>

   115       * Note that a control factory must be public and must have a public

   116       * constructor that accepts no arguments.

   117       * In cases where the factory is in a named module then it must be in a

   118       * package which is exported by that module to the {@code java.naming}

   119       * module.

   120       *

   121       * @param ctl The non-null control object containing the OID and BER data.

   122       * @param ctx The possibly null context in which the control is being created.

   123       * If null, no such information is available.

   124       * @param env The possibly null environment of the context. This is used

   125       * to find the value of the {@code LdapContext.CONTROL_FACTORIES} property.

   126       * @return A control object created using {@code ctl}; or

   127       *         {@code ctl} if a control object cannot be created using

   128       *         the algorithm described above.

   129       * @exception NamingException if a naming exception was encountered

   130       *         while attempting to create the control object.

   131       *         If one of the factories accessed throws an

   132       *         exception, it is propagated up to the caller.

   133       * If an error was encountered while loading

   134       * and instantiating the factory and object classes, the exception

   135       * is wrapped inside a {@code NamingException} and then rethrown.

   136       */

   137     public static Control getControlInstance(Control ctl, Context ctx,

   138                                              Hashtable<?,?> env)

   139         throws NamingException {

   140 

   141         // Get object factories list from environment properties or

   142         // provider resource file.

   143         FactoryEnumeration factories = ResourceManager.getFactories(

   144             LdapContext.CONTROL_FACTORIES, env, ctx);

   145 

   146         if (factories == null) {

   147             return ctl;

   148         }

   149 

   150         // Try each factory until one succeeds

   151         Control answer = null;

   152         ControlFactory factory;

   153         while (answer == null && factories.hasMore()) {

   154             factory = (ControlFactory)factories.next();

   155             answer = factory.getControlInstance(ctl);

   156         }

   157 

   158         return (answer != null)? answer : ctl;

   159     }

   160 }