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Provides a naming service for Java&nbsp;IDL. The Object Request Broker Daemon
(ORBD) also includes both a transient and persistent naming service.
The package and all its classes and interfaces
were generated by running the tool <code>idlj</code> on the file
<code>nameservice.idl</code>, which is a module written in OMG IDL.
<H3>Package Specification</H3>
<P>For a precise list of supported sections of official specifications with which
the Java[tm] Platform, Standard Edition 6, ORB complies, see <A
HREF="../CORBA/doc-files/compliance.html">Official Specifications for CORBA
support in Java[tm] SE 6</A>.
The package <tt>org.omg.CosNaming</tt> contains two public interfaces
and several auxiliary classes.
The interfaces are:
These two interfaces provide the means to bind/unbind names and object
references, to retrieve bound object references, and
to iterate through a list of bindings. The <code>NamingContext</code>
interface supplies the main functionality for the naming service, and
<code>BindingIterator</code> provides a means of iterating through a list
of name/object reference bindings.
<H2>Auxiliary Classes</H2>
In order to map an OMG IDL interface to the Java programming language,
the idlj compiler creates Java classes that can be thought of
as auxiliary classes.
Comments for the generated auxiliary classes
used by the interfaces <code>NamingContext</code> and
<code>BindingIterator</code> are included here.
<H3>Classes Used by <code>NamingContext</code> and
The following are classes used by
the naming service. (Helper and holder classes, which are
generated for each of the classes listed here, are discussed below.)
<LI><code>public final class <B>NameComponent</B></code> --
a building block for names. (Names are bound to object references
in a naming context.)
<P>A name is an array of one or more <code>NameComponent</code> objects.
A name with a single <code>NameComponent</code> is called
a <I>simple name</I>; a name with multiple <code>NameComponent</code>
objects is called a <I>compound name</I>.
A <code><B>NameComponent</B></code> object consists of two fields:
<LI><code><B>id</B></code> -- a <code>String</code> used as an identifier
<LI><code><B>kind</B></code> -- a <code>String</code> that can be used for
descriptive purpose. Its importance is that it
can be used to describe an object without affecting syntax.
The C programming language, for example, uses the the syntactic convention
of appending the extension ".c" to a file name to indicate that it is
a source code file. In a <code>NameComponent</code> object,
the <code>kind</code> field can be used to describe the type of object
rather than a file extension or some other syntactic convention.
Examples of the value of the <code>kind</code> field include the strings
<code>"c_source"</code>, <code>"object_code"</code>,
<code>"postscript"</code>, and <code>""</code>. It is not unusual
for the <code>kind</code> field to be the empty string.
In a name, each <code>NameComponent</code> object except the last denotes
a <code>NamingContext</code> object; the last <code>NameComponent</code>
object denotes the bound object reference.
This is similar to a path name, in which the last name is the
file name, and all names before it are directory names.<p>
<LI><code>public final class <B>Binding</B></code> --
an object that associates a name with an object reference or a
naming context.
A <code>Binding</code> object has two fields:
<LI><code><B>binding_name</B></code> - an array of one or more
<code>NameComponent</code> objects that represents the bound name
<LI><code><B>binding_type</B></code> - a <code>BindingType</code> object
indicating whether the binding is between a name and an object
reference or between a name and a naming context
The interface <code>NamingContext</code> has methods for
binding/unbinding names with object references or naming contexts,
for listing bindings,
and for resolving bindings (given a name, the method
<code>resolve</code> returns the object reference bound to it).
<LI><code>public final class <B>BindingType</B></code> --
an object that specifies whether the given <code>Binding</code>
object is a binding between a name and an object reference (that is,
not a naming context) or between a name and a naming context.
The class<code>BindingType</code> consists of two methods and
four constants. Two of these constants are
<code>BindingType</code> objects, and two are <code>int</code>s.
The <code>BindingType</code> objects
can be passed to the constructor for the class
<code>Binding</code> or used as parameters or return values. These
<code>BindingType</code> objects are:
<LI><code>public static final BindingType <B>nobject</B></code> --
to indicate that the binding is with an object reference
<LI><code>public static final BindingType <B>ncontext</B></code> --
to indicate that the binding is with a naming context
The <code>int</code> constants can be supplied to the method
<code>from_int</code> to create <code>BindingType</code> objects,
or they can be return values for the method <code>value</code>.
These constants are:
<LI><code>public static final int <B>_nobject</B></code>
<LI><code>public static final int <B>_ncontext</B></code>
If the method <code>from_int</code> is supplied with anything other
than <code>_nobject</code>
or <code>_ncontext</code>, it will throw
the exception <code>org.omg.CORBA.BAD_PARAM</code>.
<P>Usage is as follows:
BindingType btObject = from_int(_nobject);
BindingType btContext = from_int(_ncontext);
The variable <code>btObject</code> refers to a <code>BindingType</code>
object initialized to represent a binding with an object reference.
The variable <code>btContext</code> refers to a <code>BindingType</code>
object initialized to represent a binding with a
<code>NamingContex</code> object.
The method <code>value</code> returns either
<code>_nobject</code> or <code>_ncontext</code>, so
in the following line of code, the variable <code>bt</code>
will contain <code>_nobject</code> or <code>_ncontext</code>:
int bt = BindingType.value();
<H3>Holder Classes</H3>
OMG IDL uses OUT and INOUT parameters for returning values from operations.
The mapping to the Java programming language, which does not have OUT
and INOUT parameters, creates a special class for each type, called
a holder class.
An instance of a holder class can be passed to a
Java method as a parameter, and
a value can be assigned to its <code>value</code> field. This allows
it to perform the function of an OUT or INOUT parameter.
<P>The following holder classes are generated for the package
Note that in the <code>org.omg.CORBA</code> package,
there is a holder class for each of the basic Java types:
<code>IntHolder</code>, <code>ShortHolder</code>,
<code>StringHolder</code>, and so on.
Note also that there is a <code>NameHolder</code> class even though
there is no <code>Name</code> class; similarly, there is a
<code>BindingListHolder</code> class even though there is no
<code>BindingList</code> class. This is true because in the OMG IDL
interface, <code>Name</code> and <code>BindingList</code> are
<code>typedef</code>s. There is no mapping from an IDL
<code>typedef</code> to a Java construct, but holder classes
are generated if the <code>typedef</code> is for a sequence or
an array. As mapped to the
Java programming language, <code>Name</code> is an array of
<code>NameComponent</code> objects, and a <code>BindingList</code>
is an array of <code>Binding</code> objects.
All holder classes have at least two constructors and one field:
<LI><code><B>value</B></code> field -- an instance of the type being used as
an OUT or INOUT parameter. For example, the <code>value</code> field of a
<code>NamingContextHolder</code> will be a <code>NamingContext</code>
<LI>default constructor -- a constructor that creates a new holder object
initialized with the default value for the type. For example, a new
<code>BindingHolder</code> object created with the default constructor
will have its <code>value</code> field set to <code>null</code> because
that is the default value for an object. Other defaults are
<code>false</code> for <code>boolean</code>,
<code>0</code> for numeric and char types, and
<code>null</code> for object references.
<LI>constructor from an instance -- a constructor that creates a new
holder object whose <code>value</code> field is
initialized with the instance supplied
A holder class for a user-defined type (a Java class) has three more
methods, but application developers do not use them directly.
<H3>Helper Classes</H3>
Helper classes, which are generated for all user-defined types
in an OMG IDL interface, supply static methods needed to manipulate
those types.
There is only one method in a helper class that an
application programmer uses: the
method <code>narrow</code>. Only Java interfaces mapped from IDL
interfaces will have a helper class that includes a <code>narrow</code>
method, so in the <code>CosNaming</code> package, only the classes
<code>NamingContextHelper</code> and <code>BindingIteratorHelper</code>
have a <code>narrow</code> method.
<LI><code>public static NamingContext
<B>narrow</B>(org.omg.CORBA.Object obj)</code> -- converts the given
CORBA object to a <code>NamingContext</code> object
<LI><code>public static BindingIterator
<B>narrow</B>(org.omg.CORBA.Object obj)</code> -- converts the given
CORBA object to a <code>BindingIterator</code> object
<H2>Package <code>org.omg.CosNaming.NamingContextPackage</code></H2>
This package supplies Helper and Holder classes for the exceptions used
in the package <code>org.omg.CosNaming</code> and also for the class
<code>NotFoundReason</code>, which supplies a reason for the exception
There are Helper and Holder classes for the following exceptions:
<h2>Naming Service Compatibility</h2>
Sun's implementation of the <code>CosNaming</code> package complies
with the OMG <code>COSNaming</code> specification. In other words,
the APIs in Sun's naming service are implemented according to the
guidelines for a naming service provided by OMG. Therefore, if a
third-party vendor has implemented a naming service that is OMG
compliant, it is possible to switch between Sun's implementation of
<code>CosNaming</code> and the third-party vendor's implementation.
However, it is important to understand that there can be minor
variations in the way different vendors implement the naming service,
such as differences in the exception strings.
<h3>Instructions for Using a Third Party's Naming Service</h3>
Although we encourage using an ORB and ORB services that are both
from one vendor, it is possible to plug in a third party's
<code>COSNaming</code> implementation with Sun's RMI-IIOP ORB.
Here are the steps to follow:
<LI>Create a properties file for the Bootstrap server and give it
two entries. For example, you could call this properties file
<code>/tmp/services</code> and put the following in it:
<code>NameService, &lt;Stringified IOR of the Root Naming
This associates <code>NameService</code> with the Root Naming
Context of the <code>CosNaming</code> implementation that you
want to use.
<LI>Start the standalone Bootstrap server using the following command:
java -classpath $(CLASSPATH) -InitialServicesFile
"/tmp/services" [-ORBInitialPort port]
Note that the square brackets at the end of the command indicate that
specifying a port number is optional.
Now when an application calls the method
<code>org.omg.CORBA.ORB.resolve_initial_references</code>, CORBA
processes will contact the Bootstrap Server to get the Root Naming
<h2>Package Specification</h2>
<li>Interoperable Naming Service (<a
<h2>Related Documentation</h2>
For an overview and examples of how to use the
<code>CosNaming</code> API, please see:
<li><a href="../../../../technotes/guides/idl/tnameserv.html">
Naming Service</a>
For an overview of Java&nbsp;IDL, please see:
<li><a href="../../../../technotes/guides/idl/index.html">
Java&nbsp;IDL home page</a>
@since JDK1.3