1 /*
2 * Copyright 1999-2004 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.naming.spi;
27
28 import java.util.Hashtable;
29
30 import javax.naming;
31
32 /**
33 * This interface represents a factory for creating an object.
34 *<p>
35 * The JNDI framework allows for object implementations to
36 * be loaded in dynamically via <em>object factories</em>.
37 * For example, when looking up a printer bound in the name space,
38 * if the print service binds printer names to References, the printer
39 * Reference could be used to create a printer object, so that
40 * the caller of lookup can directly operate on the printer object
41 * after the lookup.
42 * <p>An <tt>ObjectFactory</tt> is responsible
43 * for creating objects of a specific type. In the above example,
44 * you may have a PrinterObjectFactory for creating Printer objects.
45 *<p>
46 * An object factory must implement the <tt>ObjectFactory</tt> interface.
47 * In addition, the factory class must be public and must have a
48 * public constructor that accepts no parameters.
49 *<p>
50 * The <tt>getObjectInstance()</tt> method of an object factory may
51 * be invoked multiple times, possibly using different parameters.
52 * The implementation is thread-safe.
53 *<p>
54 * The mention of URL in the documentation for this class refers to
55 * a URL string as defined by RFC 1738 and its related RFCs. It is
56 * any string that conforms to the syntax described therein, and
57 * may not always have corresponding support in the java.net.URL
58 * class or Web browsers.
59 *
60 * @author Rosanna Lee
61 * @author Scott Seligman
62 *
63 * @see NamingManager#getObjectInstance
64 * @see NamingManager#getURLContext
65 * @see ObjectFactoryBuilder
66 * @see StateFactory
67 * @since 1.3
68 */
69
70 public interface ObjectFactory {
71 /**
72 * Creates an object using the location or reference information
73 * specified.
74 * <p>
75 * Special requirements of this object are supplied
76 * using <code>environment</code>.
77 * An example of such an environment property is user identity
78 * information.
79 *<p>
80 * <tt>NamingManager.getObjectInstance()</tt>
81 * successively loads in object factories and invokes this method
82 * on them until one produces a non-null answer. When an exception
83 * is thrown by an object factory, the exception is passed on to the caller
84 * of <tt>NamingManager.getObjectInstance()</tt>
85 * (and no search is made for other factories
86 * that may produce a non-null answer).
87 * An object factory should only throw an exception if it is sure that
88 * it is the only intended factory and that no other object factories
89 * should be tried.
90 * If this factory cannot create an object using the arguments supplied,
91 * it should return null.
92 *<p>
93 * A <em>URL context factory</em> is a special ObjectFactory that
94 * creates contexts for resolving URLs or objects whose locations
95 * are specified by URLs. The <tt>getObjectInstance()</tt> method
96 * of a URL context factory will obey the following rules.
97 * <ol>
98 * <li>If <code>obj</code> is null, create a context for resolving URLs of the
99 * scheme associated with this factory. The resulting context is not tied
100 * to a specific URL: it is able to handle arbitrary URLs with this factory's
101 * scheme id. For example, invoking <tt>getObjectInstance()</tt> with
102 * <code>obj</code> set to null on an LDAP URL context factory would return a
103 * context that can resolve LDAP URLs
104 * such as "ldap://ldap.wiz.com/o=wiz,c=us" and
105 * "ldap://ldap.umich.edu/o=umich,c=us".
106 * <li>
107 * If <code>obj</code> is a URL string, create an object (typically a context)
108 * identified by the URL. For example, suppose this is an LDAP URL context
109 * factory. If <code>obj</code> is "ldap://ldap.wiz.com/o=wiz,c=us",
110 * getObjectInstance() would return the context named by the distinguished
111 * name "o=wiz, c=us" at the LDAP server ldap.wiz.com. This context can
112 * then be used to resolve LDAP names (such as "cn=George")
113 * relative to that context.
114 * <li>
115 * If <code>obj</code> is an array of URL strings, the assumption is that the
116 * URLs are equivalent in terms of the context to which they refer.
117 * Verification of whether the URLs are, or need to be, equivalent is up
118 * to the context factory. The order of the URLs in the array is
119 * not significant.
120 * The object returned by getObjectInstance() is like that of the single
121 * URL case. It is the object named by the URLs.
122 * <li>
123 * If <code>obj</code> is of any other type, the behavior of
124 * <tt>getObjectInstance()</tt> is determined by the context factory
125 * implementation.
126 * </ol>
127 *
128 * <p>
129 * The <tt>name</tt> and <tt>environment</tt> parameters
130 * are owned by the caller.
131 * The implementation will not modify these objects or keep references
132 * to them, although it may keep references to clones or copies.
133 *
134 * <p>
135 * <b>Name and Context Parameters.</b>
136 * <a name=NAMECTX></a>
137 *
138 * The <code>name</code> and <code>nameCtx</code> parameters may
139 * optionally be used to specify the name of the object being created.
140 * <code>name</code> is the name of the object, relative to context
141 * <code>nameCtx</code>.
142 * If there are several possible contexts from which the object
143 * could be named -- as will often be the case -- it is up to
144 * the caller to select one. A good rule of thumb is to select the
145 * "deepest" context available.
146 * If <code>nameCtx</code> is null, <code>name</code> is relative
147 * to the default initial context. If no name is being specified, the
148 * <code>name</code> parameter should be null.
149 * If a factory uses <code>nameCtx</code> it should synchronize its use
150 * against concurrent access, since context implementations are not
151 * guaranteed to be thread-safe.
152 * <p>
153 *
154 * @param obj The possibly null object containing location or reference
155 * information that can be used in creating an object.
156 * @param name The name of this object relative to <code>nameCtx</code>,
157 * or null if no name is specified.
158 * @param nameCtx The context relative to which the <code>name</code>
159 * parameter is specified, or null if <code>name</code> is
160 * relative to the default initial context.
161 * @param environment The possibly null environment that is used in
162 * creating the object.
163 * @return The object created; null if an object cannot be created.
164 * @exception Exception if this object factory encountered an exception
165 * while attempting to create an object, and no other object factories are
166 * to be tried.
167 *
168 * @see NamingManager#getObjectInstance
169 * @see NamingManager#getURLContext
170 */
171 public Object getObjectInstance(Object obj, Name name, Context nameCtx,
172 Hashtable<?,?> environment)
173 throws Exception;
174 }
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