DirObjectFactory


1   /*
2    * @(#)DirObjectFactory.java    1.11 04/07/16
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.naming.spi;
9   
10  import java.util.Hashtable  ;
11  import javax.naming.*;
12  import javax.naming.directory.Attributes  ;
13  
14  /**
15    * This interface represents a factory for creating an object given
16    * an object and attributes about the object.
17    *<p>
18    * The JNDI framework allows for object implementations to
19    * be loaded in dynamically via <em>object factories</em>. See
20    * <tt>ObjectFactory</tt> for details.
21    * <p>
22    * A <tt>DirObjectFactory</tt> extends <tt>ObjectFactory</tt> by allowing 
23    * an <tt>Attributes</tt> instance
24    * to be supplied to the <tt>getObjectInstance()</tt> method.
25    * <tt>DirObjectFactory</tt> implementations are intended to be used by <tt>DirContext</tt>
26    * service providers. The service provider, in addition reading an
27    * object from the directory, might already have attributes that
28    * are useful for the object factory to check to see whether the
29    * factory is supposed to process the object. For instance, an LDAP-style
30    * service provider might have read the "objectclass" of the object.
31    * A CORBA object factory might be interested only in LDAP entries
32    * with "objectclass=corbaObject". By using the attributes supplied by
33    * the LDAP service provider, the CORBA object factory can quickly
34    * eliminate objects that it need not worry about, and non-CORBA object
35    * factories can quickly eliminate CORBA-related LDAP entries.
36    *
37    * @author Rosanna Lee
38    * @author Scott Seligman
39    * @version 1.11 04/07/16
40    *
41    * @see NamingManager#getObjectInstance
42    * @see DirectoryManager#getObjectInstance
43    * @see ObjectFactory
44    * @since 1.3
45    */
46  
47  public interface DirObjectFactory extends ObjectFactory   {
48  /**
49   * Creates an object using the location or reference information, and attributes
50   * specified.  
51   * <p>
52   * Special requirements of this object are supplied
53   * using <code>environment</code>.
54   * An example of such an environment property is user identity
55   * information. 
56   *<p>
57   * <tt>DirectoryManager.getObjectInstance()</tt>
58   * successively loads in object factories. If it encounters a <tt>DirObjectFactory</tt>,
59   * it will invoke <tt>DirObjectFactory.getObjectInstance()</tt>; 
60   * otherwise, it invokes
61   * <tt>ObjectFactory.getObjectInstance()</tt>. It does this until a factory
62   * produces a non-null answer.  
63   * <p> When an exception
64   * is thrown by an object factory, the exception is passed on to the caller
65   * of <tt>DirectoryManager.getObjectInstance()</tt>. The search for other factories
66   * that may produce a non-null answer is halted. 
67   * An object factory should only throw an exception if it is sure that
68   * it is the only intended factory and that no other object factories
69   * should be tried.
70   * If this factory cannot create an object using the arguments supplied,
71   * it should return null. 
72    *<p>Since <tt>DirObjectFactory</tt> extends <tt>ObjectFactory</tt>, it 
73    * effectively
74    * has two <tt>getObjectInstance()</tt> methods, where one differs from the other by
75    * the attributes argument. Given a factory that implements <tt>DirObjectFactory</tt>,
76    * <tt>DirectoryManager.getObjectInstance()</tt> will only
77    * use the method that accepts the attributes argument, while 
78    * <tt>NamingManager.getObjectInstance()</tt> will only use the one that does not accept
79    * the attributes argument.
80   *<p>
81   * See <tt>ObjectFactory</tt> for a description URL context factories and other
82   * properties of object factories that apply equally to <tt>DirObjectFactory</tt>.
83   *<p>
84   * The <tt>name</tt>, <tt>attrs</tt>, and <tt>environment</tt> parameters
85   * are owned by the caller.
86   * The implementation will not modify these objects or keep references
87   * to them, although it may keep references to clones or copies.
88   *
89   * @param obj The possibly null object containing location or reference 
90   *      information that can be used in creating an object.
91   * @param name The name of this object relative to <code>nameCtx</code>,
92   *      or null if no name is specified.
93   * @param nameCtx The context relative to which the <code>name</code>
94   *      parameter is specified, or null if <code>name</code> is
95   *      relative to the default initial context.
96   * @param environment The possibly null environment that is used in
97   *      creating the object.
98   * @param attrs The possibly null attributes containing some of <tt>obj</tt>'s
99   * attributes. <tt>attrs</tt> might not necessarily have all of <tt>obj</tt>'s
100  * attributes. If the object factory requires more attributes, it needs
101  * to get it, either using <tt>obj</tt>, or <tt>name</tt> and <tt>nameCtx</tt>.
102  *  The factory must not modify attrs.
103  * @return The object created; null if an object cannot be created.
104  * @exception Exception If this object factory encountered an exception
105  * while attempting to create an object, and no other object factories are
106  * to be tried.
107  *
108  * @see DirectoryManager#getObjectInstance
109  * @see NamingManager#getURLContext
110  */
111     public Object   getObjectInstance(Object   obj, Name name, Context nameCtx,
112                     Hashtable  <?,?> environment,
113                     Attributes   attrs) 
114     throws Exception  ;
115 }
116
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