001 /*
002 * Copyright 1999-2004 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.naming.spi;
027
028 import java.util.Hashtable;
029
030 import javax.naming.*;
031
032 /**
033 * This interface represents a factory for creating an object.
034 *<p>
035 * The JNDI framework allows for object implementations to
036 * be loaded in dynamically via <em>object factories</em>.
037 * For example, when looking up a printer bound in the name space,
038 * if the print service binds printer names to References, the printer
039 * Reference could be used to create a printer object, so that
040 * the caller of lookup can directly operate on the printer object
041 * after the lookup.
042 * <p>An <tt>ObjectFactory</tt> is responsible
043 * for creating objects of a specific type. In the above example,
044 * you may have a PrinterObjectFactory for creating Printer objects.
045 *<p>
046 * An object factory must implement the <tt>ObjectFactory</tt> interface.
047 * In addition, the factory class must be public and must have a
048 * public constructor that accepts no parameters.
049 *<p>
050 * The <tt>getObjectInstance()</tt> method of an object factory may
051 * be invoked multiple times, possibly using different parameters.
052 * The implementation is thread-safe.
053 *<p>
054 * The mention of URL in the documentation for this class refers to
055 * a URL string as defined by RFC 1738 and its related RFCs. It is
056 * any string that conforms to the syntax described therein, and
057 * may not always have corresponding support in the java.net.URL
058 * class or Web browsers.
059 *
060 * @author Rosanna Lee
061 * @author Scott Seligman
062 * @version 1.17 07/05/05
063 *
064 * @see NamingManager#getObjectInstance
065 * @see NamingManager#getURLContext
066 * @see ObjectFactoryBuilder
067 * @see StateFactory
068 * @since 1.3
069 */
070
071 public interface ObjectFactory {
072 /**
073 * Creates an object using the location or reference information
074 * specified.
075 * <p>
076 * Special requirements of this object are supplied
077 * using <code>environment</code>.
078 * An example of such an environment property is user identity
079 * information.
080 *<p>
081 * <tt>NamingManager.getObjectInstance()</tt>
082 * successively loads in object factories and invokes this method
083 * on them until one produces a non-null answer. When an exception
084 * is thrown by an object factory, the exception is passed on to the caller
085 * of <tt>NamingManager.getObjectInstance()</tt>
086 * (and no search is made for other factories
087 * that may produce a non-null answer).
088 * An object factory should only throw an exception if it is sure that
089 * it is the only intended factory and that no other object factories
090 * should be tried.
091 * If this factory cannot create an object using the arguments supplied,
092 * it should return null.
093 *<p>
094 * A <em>URL context factory</em> is a special ObjectFactory that
095 * creates contexts for resolving URLs or objects whose locations
096 * are specified by URLs. The <tt>getObjectInstance()</tt> method
097 * of a URL context factory will obey the following rules.
098 * <ol>
099 * <li>If <code>obj</code> is null, create a context for resolving URLs of the
100 * scheme associated with this factory. The resulting context is not tied
101 * to a specific URL: it is able to handle arbitrary URLs with this factory's
102 * scheme id. For example, invoking <tt>getObjectInstance()</tt> with
103 * <code>obj</code> set to null on an LDAP URL context factory would return a
104 * context that can resolve LDAP URLs
105 * such as "ldap://ldap.wiz.com/o=wiz,c=us" and
106 * "ldap://ldap.umich.edu/o=umich,c=us".
107 * <li>
108 * If <code>obj</code> is a URL string, create an object (typically a context)
109 * identified by the URL. For example, suppose this is an LDAP URL context
110 * factory. If <code>obj</code> is "ldap://ldap.wiz.com/o=wiz,c=us",
111 * getObjectInstance() would return the context named by the distinguished
112 * name "o=wiz, c=us" at the LDAP server ldap.wiz.com. This context can
113 * then be used to resolve LDAP names (such as "cn=George")
114 * relative to that context.
115 * <li>
116 * If <code>obj</code> is an array of URL strings, the assumption is that the
117 * URLs are equivalent in terms of the context to which they refer.
118 * Verification of whether the URLs are, or need to be, equivalent is up
119 * to the context factory. The order of the URLs in the array is
120 * not significant.
121 * The object returned by getObjectInstance() is like that of the single
122 * URL case. It is the object named by the URLs.
123 * <li>
124 * If <code>obj</code> is of any other type, the behavior of
125 * <tt>getObjectInstance()</tt> is determined by the context factory
126 * implementation.
127 * </ol>
128 *
129 * <p>
130 * The <tt>name</tt> and <tt>environment</tt> parameters
131 * are owned by the caller.
132 * The implementation will not modify these objects or keep references
133 * to them, although it may keep references to clones or copies.
134 *
135 * <p>
136 * <b>Name and Context Parameters.</b>
137 * <a name=NAMECTX></a>
138 *
139 * The <code>name</code> and <code>nameCtx</code> parameters may
140 * optionally be used to specify the name of the object being created.
141 * <code>name</code> is the name of the object, relative to context
142 * <code>nameCtx</code>.
143 * If there are several possible contexts from which the object
144 * could be named -- as will often be the case -- it is up to
145 * the caller to select one. A good rule of thumb is to select the
146 * "deepest" context available.
147 * If <code>nameCtx</code> is null, <code>name</code> is relative
148 * to the default initial context. If no name is being specified, the
149 * <code>name</code> parameter should be null.
150 * If a factory uses <code>nameCtx</code> it should synchronize its use
151 * against concurrent access, since context implementations are not
152 * guaranteed to be thread-safe.
153 * <p>
154 *
155 * @param obj The possibly null object containing location or reference
156 * information that can be used in creating an object.
157 * @param name The name of this object relative to <code>nameCtx</code>,
158 * or null if no name is specified.
159 * @param nameCtx The context relative to which the <code>name</code>
160 * parameter is specified, or null if <code>name</code> is
161 * relative to the default initial context.
162 * @param environment The possibly null environment that is used in
163 * creating the object.
164 * @return The object created; null if an object cannot be created.
165 * @exception Exception if this object factory encountered an exception
166 * while attempting to create an object, and no other object factories are
167 * to be tried.
168 *
169 * @see NamingManager#getObjectInstance
170 * @see NamingManager#getURLContext
171 */
172 public Object getObjectInstance(Object obj, Name name,
173 Context nameCtx, Hashtable<?, ?> environment)
174 throws Exception;
175 }
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