Java tutorial
/* * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved. * 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 * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * 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. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.naming.spi; import java.util.Hashtable; import javax.naming.*; /** * This interface represents a factory for creating an object. *<p> * The JNDI framework allows for object implementations to * be loaded in dynamically via <em>object factories</em>. * For example, when looking up a printer bound in the name space, * if the print service binds printer names to References, the printer * Reference could be used to create a printer object, so that * the caller of lookup can directly operate on the printer object * after the lookup. * <p>An {@code ObjectFactory} is responsible * for creating objects of a specific type. In the above example, * you may have a PrinterObjectFactory for creating Printer objects. *<p> * An object factory must implement the {@code ObjectFactory} interface. * In addition, the factory class must be public and must have a * public constructor that accepts no parameters. * Note that in cases where the factory is in a named module then it must be * in a package which is exported by that module to the {@code java.naming} * module. *<p> * The {@code getObjectInstance()} method of an object factory may * be invoked multiple times, possibly using different parameters. * The implementation is thread-safe. *<p> * The mention of URL in the documentation for this class refers to * a URL string as defined by RFC 1738 and its related RFCs. It is * any string that conforms to the syntax described therein, and * may not always have corresponding support in the java.net.URL * class or Web browsers. * * @author Rosanna Lee * @author Scott Seligman * * @see NamingManager#getObjectInstance * @see NamingManager#getURLContext * @see ObjectFactoryBuilder * @see StateFactory * @since 1.3 */ public interface ObjectFactory { /** * Creates an object using the location or reference information * specified. * <p> * Special requirements of this object are supplied * using {@code environment}. * An example of such an environment property is user identity * information. *<p> * {@code NamingManager.getObjectInstance()} * successively loads in object factories and invokes this method * on them until one produces a non-null answer. When an exception * is thrown by an object factory, the exception is passed on to the caller * of {@code NamingManager.getObjectInstance()} * (and no search is made for other factories * that may produce a non-null answer). * An object factory should only throw an exception if it is sure that * it is the only intended factory and that no other object factories * should be tried. * If this factory cannot create an object using the arguments supplied, * it should return null. *<p> * A <em>URL context factory</em> is a special ObjectFactory that * creates contexts for resolving URLs or objects whose locations * are specified by URLs. The {@code getObjectInstance()} method * of a URL context factory will obey the following rules. * <ol> * <li>If {@code obj} is null, create a context for resolving URLs of the * scheme associated with this factory. The resulting context is not tied * to a specific URL: it is able to handle arbitrary URLs with this factory's * scheme id. For example, invoking {@code getObjectInstance()} with * {@code obj} set to null on an LDAP URL context factory would return a * context that can resolve LDAP URLs * such as "ldap://ldap.wiz.com/o=wiz,c=us" and * "ldap://ldap.umich.edu/o=umich,c=us". * <li> * If {@code obj} is a URL string, create an object (typically a context) * identified by the URL. For example, suppose this is an LDAP URL context * factory. If {@code obj} is "ldap://ldap.wiz.com/o=wiz,c=us", * getObjectInstance() would return the context named by the distinguished * name "o=wiz, c=us" at the LDAP server ldap.wiz.com. This context can * then be used to resolve LDAP names (such as "cn=George") * relative to that context. * <li> * If {@code obj} is an array of URL strings, the assumption is that the * URLs are equivalent in terms of the context to which they refer. * Verification of whether the URLs are, or need to be, equivalent is up * to the context factory. The order of the URLs in the array is * not significant. * The object returned by getObjectInstance() is like that of the single * URL case. It is the object named by the URLs. * <li> * If {@code obj} is of any other type, the behavior of * {@code getObjectInstance()} is determined by the context factory * implementation. * </ol> * * <p> * The {@code name} and {@code environment} parameters * are owned by the caller. * The implementation will not modify these objects or keep references * to them, although it may keep references to clones or copies. * * <p> * <b>Name and Context Parameters.</b> * <a id=NAMECTX></a> * * The {@code name} and {@code nameCtx} parameters may * optionally be used to specify the name of the object being created. * {@code name} is the name of the object, relative to context * {@code nameCtx}. * If there are several possible contexts from which the object * could be named -- as will often be the case -- it is up to * the caller to select one. A good rule of thumb is to select the * "deepest" context available. * If {@code nameCtx} is null, {@code name} is relative * to the default initial context. If no name is being specified, the * {@code name} parameter should be null. * If a factory uses {@code nameCtx} it should synchronize its use * against concurrent access, since context implementations are not * guaranteed to be thread-safe. * * @param obj The possibly null object containing location or reference * information that can be used in creating an object. * @param name The name of this object relative to {@code nameCtx}, * or null if no name is specified. * @param nameCtx The context relative to which the {@code name} * parameter is specified, or null if {@code name} is * relative to the default initial context. * @param environment The possibly null environment that is used in * creating the object. * @return The object created; null if an object cannot be created. * @exception Exception if this object factory encountered an exception * while attempting to create an object, and no other object factories are * to be tried. * * @see NamingManager#getObjectInstance * @see NamingManager#getURLContext */ public Object getObjectInstance(Object obj, Name name, Context nameCtx, Hashtable<?, ?> environment) throws Exception; }