orbremotecontext.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 628 行 · 第 1/2 页

     *
     * @param name the name of the object to look up
     * @return	the object bound to <tt>name</tt>, not following the
     * terminal link (if any)
     * @throws	NamingException if a naming exception is encountered
     */
    public Object lookupLink(String name) throws NamingException {
        return wrap(_context.lookupLink(name));
    }

    /**
     * Retrieves the parser associated with the named context.
     *
     * @param name the name of the context from which to get the parser
     * @return	a name parser that can parse compound names into their atomic
     * components
     * @throws	NamingException if a naming exception is encountered
     */
    public NameParser getNameParser(Name name) throws NamingException {
        return _context.getNameParser(name);
    }

    /**
     * Retrieves the parser associated with the named context.
     *
     * @param name the name of the context from which to get the parser
     * @return	a name parser that can parse compound names into their atomic
     * components
     * @throws	NamingException if a naming exception is encountered
     */
    public NameParser getNameParser(String name) throws NamingException {
        return _context.getNameParser(name);
    }

    /**
     * Composes the name of this context with a name relative to
     * this context.
     *
     * @param name   a name relative to this context
     * @param prefix the name of this context relative to one of its ancestors
     * @return	the composition of <code>prefix</code> and <code>name</code>
     * @throws	NamingException if a naming exception is encountered
     */
    public Name composeName(Name name, Name prefix) throws NamingException {
        return _context.composeName(name, prefix);
    }

    /**
     * Composes the name of this context with a name relative to
     * this context.
     *
     * @param name   a name relative to this context
     * @param prefix the name of this context relative to one of its ancestors
     * @return	the composition of <code>prefix</code> and <code>name</code>
     * @throws	NamingException if a naming exception is encountered
     */
    public String composeName(String name, String prefix)
            throws NamingException {
        return _context.composeName(name, prefix);
    }

    /**
     * Adds a new environment property to the environment of this
     * context.  If the property already exists, its value is overwritten.
     *
     * @param propName the name of the environment property to add; may not be null
     * @param propVal  the value of the property to add; may not be null
     * @return	the previous value of the property, or null if the property was
     * not in the environment before
     * @throws	NamingException if a naming exception is encountered
     */
    public Object addToEnvironment(String propName, Object propVal)
            throws NamingException {
        return _context.addToEnvironment(propName, propVal);
    }

    /**
     * Removes an environment property from the environment of this
     * context.  See class description for more details on environment
     * properties.
     *
     * @param propName the name of the environment property to remove; may not be null
     * @return	the previous value of the property, or null if the property was
     * not in the environment
     * @throws	NamingException if a naming exception is encountered
     */
    public Object removeFromEnvironment(String propName)
            throws NamingException {
        return _context.removeFromEnvironment(propName);
    }

    /**
     * Retrieves the environment in effect for this context.
     *
     * @return	the environment of this context; never null
     * @throws	NamingException if a naming exception is encountered
     */
    public Hashtable getEnvironment() throws NamingException {
        return _context.getEnvironment();
    }

    /**
     * Closes this context.
     *
     * @throws	NamingException if a naming exception is encountered
     */
    public void close() throws NamingException {
        if (_context != null) {
            if (dereference() <= 0) {
                Object provider = getEnvironment().get(
                        RemoteContext.NAMING_PROVIDER);
                if (provider instanceof Proxy) {
                    ((Proxy) provider).disposeProxy();
                }
            }
            _context.close();
            _context = null;
        }
    }

    /**
     * Retrieves the full name of this context within its own namespace.
     *
     * @return	this context's name in its own namespace; never null
     * @throws	NamingException if a naming exception is encountered
     */
    public String getNameInNamespace() throws NamingException {
        return _context.getNameInNamespace();
    }

    /**
     * Called by the garbage collector on an object when garbage collection
     * determines that there are no more references to the object.
     *
     * @throws Throwable the <code>Exception</code> raised by this method
     */
    protected void finalize() throws Throwable {
        close();
    }

    /**
     * Wrap the supplied object in an <code>ORBRemoteContext</code> iff it
     * is an instance of <code>RemoteContext</code>, otherwise returns the
     * object unchanged.
     *
     * @param object the object to wrap
     * @return the supplied object in an <code>ORBRemoteContext</code> iff it
     * is an instance of <code>RemoteContext</code>, otherwise returns the
     * object unchanged.
     * @throws NamingException if a naming exception is encountered
     */
    private Object wrap(Object object) throws NamingException {
        if (object instanceof RemoteContext) {
            return new ORBRemoteContext((RemoteContext) object);
        }
        return object;
    }

    /**
     * Increment the reference count of the provider. This is the number
     * of <code>Context</code> instances that refer to it.
     *
     * @throws NamingException for any naming error
     */
    private void reference() throws NamingException {
        Ref ref = (Ref) _context.getEnvironment().get(REFERENCE_KEY);
        if (ref == null) {
            ref = new Ref();
            _context.addToEnvironment(REFERENCE_KEY, ref);
        }
        ref.inc();
    }

    /**
     * Dereference the reference count of the provider.
     *
     * @return the number of references
     * @throws NamingException for any naming error
     */
    private int dereference() throws NamingException {
        Ref ref = (Ref) _context.getEnvironment().get(REFERENCE_KEY);
        return (ref != null) ? ref.dec() : 0;
    }


    /**
     * Helper to wrap any <code>RemoteContext</code> instances returned
     * by a <code>NamingEnumeration</code> in <code>ORBRemoteContext</code>
     * instances.
     */
    private static class ORBNamingEnumeration implements NamingEnumeration {

        /**
         * The enumeration.
         */
        private final NamingEnumeration _iterator;

        /**
         * Construct a new <code>ORBNamingEnumeration</code>.
         *
         * @param iterator the enumeration to delegate to
         */
        private ORBNamingEnumeration(NamingEnumeration iterator) {
            _iterator = iterator;
        }

        /**
         * Retrieves the next element in the enumeration.
         *
         * @return the next element in the enumeration.
         * @throws NamingException for any naming error
         * @throws java.util.NoSuchElementException If attempting to get the next element when none is available.
         */
        public Object next() throws NamingException {
            return wrap(_iterator.next());
        }

        /**
         * Determines whether there are any more elements in the enumeration.
         *
         * @throws NamingException for any naming error.
         * @return		true if there is more in the enumeration; false otherwise.
         */
        public boolean hasMore() throws NamingException {
            return _iterator.hasMore();
        }

        /**
         * Closes this enumeration.
         *
         * @throws NamingException for any naming error
         */
        public void close() throws NamingException {
            _iterator.close();
        }

        /**
         * Tests if this enumeration contains more elements.
         *
         * @return <code>true</code> if and only if this enumeration object
         *         contains at least one more element to provide;
         *         <code>false</code> otherwise.
         */
        public boolean hasMoreElements() {
            return _iterator.hasMoreElements();
        }

        /**
         * Returns the next element of this enumeration if this enumeration
         * object has at least one more element to provide.
         *
         * @return the next element of this enumeration.
         * @throws java.util.NoSuchElementException if no more elements exist.
         */
        public Object nextElement() {
            try {
                return wrap(_iterator.nextElement());
            } catch (NamingException exception) {
                throw new NoSuchElementException(exception.getMessage());
            }
        }

        /**
         * Wraps any <code>Context</code> instances in <code>ORBRemoteContext</code>.
         *
         * @param obj the object
         * @return obj
         * @throws NamingException for any naming error
         */
        private Object wrap(Object obj) throws NamingException {
            if (obj instanceof Binding) {
                Binding binding = (Binding) obj;
                Object bound = binding.getObject();
                if (bound instanceof RemoteContext) {
                    binding.setObject(
                            new ORBRemoteContext((RemoteContext) bound));
                }
            }
            return obj;
        }
    }

    /**
     * Helper to maintain a reference count.
     */
    private static class Ref {

        /**
         * The reference count.
         */
        private int _count;

        /**
         * Increment the reference count.
         *
         * @return the reference count
         */
        public synchronized int inc() {
            return ++_count;
        }

        /**
         * Decrement the reference count.
         *
         * @return the reference count
         */
        public synchronized int dec() {
            return --_count;
        }

    }

}