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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 <tt>ObjectFactory</tt> 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 <tt>ObjectFactory</tt> interface.
* In addition, the factory class must be public and must have a
* public constructor that accepts no parameters.
*<p>
* The <tt>getObjectInstance()</tt> 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</code>.
* An example of such an environment property is user identity
* information.
*<p>
* <tt>NamingManager.getObjectInstance()</tt>
* 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 <tt>NamingManager.getObjectInstance()</tt>
* (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 <tt>getObjectInstance()</tt> method
* of a URL context factory will obey the following rules.
* <ol>
* <li>If <code>obj</code> 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 <tt>getObjectInstance()</tt> with
* <code>obj</code> 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</code> 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</code> 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</code> 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</code> is of any other type, the behavior of
* <tt>getObjectInstance()</tt> is determined by the context factory
* implementation.
* </ol>
*
* <p>
* The <tt>name</tt> and <tt>environment</tt> 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 name=NAMECTX></a>
*
* The <code>name</code> and <code>nameCtx</code> parameters may
* optionally be used to specify the name of the object being created.
* <code>name</code> is the name of the object, relative to context
* <code>nameCtx</code>.
* 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</code> is null, <code>name</code> is relative
* to the default initial context. If no name is being specified, the
* <code>name</code> parameter should be null.
* If a factory uses <code>nameCtx</code> it should synchronize its use
* against concurrent access, since context implementations are not
* guaranteed to be thread-safe.
* <p>
*
* @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</code>,
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