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This interface represents a factory for creating objects.
The JNDI framework allows for object implementations to be loaded in dynamically via "object factories." 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.
An ObjectFactory is responsible for creating objects of a specific type. In the above example, you may have a PrinterObjectFactory for creating Printer objects.
Each object factory must export the ObjectFactory interface. In addition, the factory class must be public and must have a public constructor that accepts no arguments.
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.
NamingManager.getObjectInstance(java.lang.Object, javax.naming.Name, javax.naming.Context, java.util.Hashtable)
,
NamingManager.getURLContext(java.lang.String, java.util.Hashtable)
,
ObjectFactoryBuilder
Method Summary | |
java.lang.Object |
getObjectInstance(java.lang.Object obj,
Name name,
Context nameCtx,
java.util.Hashtable environment)
Creates an object using the location or reference information specified. |
Method Detail |
public java.lang.Object getObjectInstance(java.lang.Object obj, Name name, Context nameCtx, java.util.Hashtable environment) throws java.lang.Exception
Special requirements of this object are supplied
using environment
.
An example of such an environment property is user identity
information.
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 NamingManager.getObjectInstance(). The search for other factories that may produce a non-null answer is halted. 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.
A URL context factory is a special ObjectFactory that creates contexts for resolving URLs or contexts whose location is specified by URLs. If the ObjectFactory is a URL context factory, it must use the following rules.
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 getObjectInstance() with
obj
set to null on a LDAP URL context factory would return a
context that can resolve LDAP urls
(e.g. "ldap://ldap.wiz.com/o=wiz,c=us",
"ldap://ldap.umich.edu/o=umich,c=us", ...).
obj
is URL string, create a object (typically a context)
identified by the obj
. Suppose this is an LDAP URL context
factory. If obj
is "ldap://ldap.wiz.com/o=wiz,c=us",
getObjectInstance() would return a 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 relative to that context
(e.g. cn=George).
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 a context for resolving names relative to the
context named by the URLs.
obj
is of any other type, the behavior of getObjectInstance()
is determined by the context factory.
The name
and nameCtx
parameters may
optionally be used to specify the name of the object being created.
name
is the name of the object, relative to context
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 nameCtx
is null, name
is relative
to the default initial context. If no name is being specified, the
name
parameter should be null.
obj
- The possibly null object containing location or reference
information that can be used in creating an object.name
- The name of this object relative to nameCtx
.
Specifying a name is optional; if it is
omitted, name
should be null.nameCtx
- The context relative to which the name
parameter is specified. If null, name
is
relative to the default initial context.environment
- The possibly null environment that is used in
creating the object.NamingManager.getObjectInstance(java.lang.Object, javax.naming.Name, javax.naming.Context, java.util.Hashtable)
,
NamingManager.getURLContext(java.lang.String, java.util.Hashtable)
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