Java tutorial
/* * Copyright (c) 1999, 2011, 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; import java.util.Vector; import java.util.Enumeration; /** * This class represents a reference to an object that is found outside of * the naming/directory system. *<p> * Reference provides a way of recording address information about * objects which themselves are not directly bound to the naming/directory system. *<p> * A Reference consists of an ordered list of addresses and class information * about the object being referenced. * Each address in the list identifies a communications endpoint * for the same conceptual object. The "communications endpoint" * is information that indicates how to contact the object. It could * be, for example, a network address, a location in memory on the * local machine, another process on the same machine, etc. * The order of the addresses in the list may be of significance * to object factories that interpret the reference. *<p> * Multiple addresses may arise for * various reasons, such as replication or the object offering interfaces * over more than one communication mechanism. The addresses are indexed * starting with zero. *<p> * A Reference also contains information to assist in creating an instance * of the object to which this Reference refers. It contains the class name * of that object, and the class name and location of the factory to be used * to create the object. * The class factory location is a space-separated list of URLs representing * the class path used to load the factory. When the factory class (or * any class or resource upon which it depends) needs to be loaded, * each URL is used (in order) to attempt to load the class. *<p> * A Reference instance is not synchronized against concurrent access by multiple * threads. Threads that need to access a single Reference concurrently should * synchronize amongst themselves and provide the necessary locking. * * @author Rosanna Lee * @author Scott Seligman * * @see RefAddr * @see StringRefAddr * @see BinaryRefAddr * @since 1.3 */ /*<p> * The serialized form of a Reference object consists of the class * name of the object being referenced (a String), a Vector of the * addresses (each a RefAddr), the name of the class factory (a * String), and the location of the class factory (a String). */ public class Reference implements Cloneable, java.io.Serializable { /** * Contains the fully-qualified name of the class of the object to which * this Reference refers. * @serial * @see java.lang.Class#getName */ protected String className; /** * Contains the addresses contained in this Reference. * Initialized by constructor. * @serial */ protected Vector<RefAddr> addrs = null; /** * Contains the name of the factory class for creating * an instance of the object to which this Reference refers. * Initialized to null. * @serial */ protected String classFactory = null; /** * Contains the location of the factory class. * Initialized to null. * @serial */ protected String classFactoryLocation = null; /** * Constructs a new reference for an object with class name 'className'. * Class factory and class factory location are set to null. * The newly created reference contains zero addresses. * * @param className The non-null class name of the object to which * this reference refers. */ public Reference(String className) { this.className = className; addrs = new Vector<>(); } /** * Constructs a new reference for an object with class name 'className' and * an address. * Class factory and class factory location are set to null. * * @param className The non-null class name of the object to * which this reference refers. * @param addr The non-null address of the object. */ public Reference(String className, RefAddr addr) { this.className = className; addrs = new Vector<>(); addrs.addElement(addr); } /** * Constructs a new reference for an object with class name 'className', * and the class name and location of the object's factory. * * @param className The non-null class name of the object to which * this reference refers. * @param factory The possibly null class name of the object's factory. * @param factoryLocation * The possibly null location from which to load * the factory (e.g. URL) * @see javax.naming.spi.ObjectFactory * @see javax.naming.spi.NamingManager#getObjectInstance */ public Reference(String className, String factory, String factoryLocation) { this(className); classFactory = factory; classFactoryLocation = factoryLocation; } /** * Constructs a new reference for an object with class name 'className', * the class name and location of the object's factory, and the address for * the object. * * @param className The non-null class name of the object to * which this reference refers. * @param factory The possibly null class name of the object's factory. * @param factoryLocation The possibly null location from which * to load the factory (e.g. URL) * @param addr The non-null address of the object. * @see javax.naming.spi.ObjectFactory * @see javax.naming.spi.NamingManager#getObjectInstance */ public Reference(String className, RefAddr addr, String factory, String factoryLocation) { this(className, addr); classFactory = factory; classFactoryLocation = factoryLocation; } /** * Retrieves the class name of the object to which this reference refers. * * @return The non-null fully-qualified class name of the object. * (e.g. "java.lang.String") */ public String getClassName() { return className; } /** * Retrieves the class name of the factory of the object * to which this reference refers. * * @return The possibly null fully-qualified class name of the factory. * (e.g. "java.lang.String") */ public String getFactoryClassName() { return classFactory; } /** * Retrieves the location of the factory of the object * to which this reference refers. * If it is a codebase, then it is an ordered list of URLs, * separated by spaces, listing locations from where the factory * class definition should be loaded. * * @return The possibly null string containing the * location for loading in the factory's class. */ public String getFactoryClassLocation() { return classFactoryLocation; } /** * Retrieves the first address that has the address type 'addrType'. * String.compareTo() is used to test the equality of the address types. * * @param addrType The non-null address type for which to find the address. * @return The address in this reference with address type 'addrType'; * null if no such address exists. */ public RefAddr get(String addrType) { int len = addrs.size(); RefAddr addr; for (int i = 0; i < len; i++) { addr = addrs.elementAt(i); if (addr.getType().compareTo(addrType) == 0) return addr; } return null; } /** * Retrieves the address at index posn. * @param posn The index of the address to retrieve. * @return The address at the 0-based index posn. It must be in the * range [0,getAddressCount()). * @exception ArrayIndexOutOfBoundsException If posn not in the specified * range. */ public RefAddr get(int posn) { return addrs.elementAt(posn); } /** * Retrieves an enumeration of the addresses in this reference. * When addresses are added, changed or removed from this reference, * its effects on this enumeration are undefined. * * @return An non-null enumeration of the addresses * ({@code RefAddr}) in this reference. * If this reference has zero addresses, an enumeration with * zero elements is returned. */ public Enumeration<RefAddr> getAll() { return addrs.elements(); } /** * Retrieves the number of addresses in this reference. * * @return The nonnegative number of addresses in this reference. */ public int size() { return addrs.size(); } /** * Adds an address to the end of the list of addresses. * * @param addr The non-null address to add. */ public void add(RefAddr addr) { addrs.addElement(addr); } /** * Adds an address to the list of addresses at index posn. * All addresses at index posn or greater are shifted up * the list by one (away from index 0). * * @param posn The 0-based index of the list to insert addr. * @param addr The non-null address to add. * @exception ArrayIndexOutOfBoundsException If posn not in the specified * range. */ public void add(int posn, RefAddr addr) { addrs.insertElementAt(addr, posn); } /** * Deletes the address at index posn from the list of addresses. * All addresses at index greater than posn are shifted down * the list by one (towards index 0). * * @param posn The 0-based index of in address to delete. * @return The address removed. * @exception ArrayIndexOutOfBoundsException If posn not in the specified * range. */ public Object remove(int posn) { Object r = addrs.elementAt(posn); addrs.removeElementAt(posn); return r; } /** * Deletes all addresses from this reference. */ public void clear() { addrs.setSize(0); } /** * Determines whether obj is a reference with the same addresses * (in same order) as this reference. * The addresses are checked using RefAddr.equals(). * In addition to having the same addresses, the Reference also needs to * have the same class name as this reference. * The class factory and class factory location are not checked. * If obj is null or not an instance of Reference, null is returned. * * @param obj The possibly null object to check. * @return true if obj is equal to this reference; false otherwise. */ public boolean equals(Object obj) { if ((obj != null) && (obj instanceof Reference)) { Reference target = (Reference) obj; // ignore factory information if (target.className.equals(this.className) && target.size() == this.size()) { Enumeration<RefAddr> mycomps = getAll(); Enumeration<RefAddr> comps = target.getAll(); while (mycomps.hasMoreElements()) if (!(mycomps.nextElement().equals(comps.nextElement()))) return false; return true; } } return false; } /** * Computes the hash code of this reference. * The hash code is the sum of the hash code of its addresses. * * @return A hash code of this reference as an int. */ public int hashCode() { int hash = className.hashCode(); for (Enumeration<RefAddr> e = getAll(); e.hasMoreElements();) hash += e.nextElement().hashCode(); return hash; } /** * Generates the string representation of this reference. * The string consists of the class name to which this reference refers, * and the string representation of each of its addresses. * This representation is intended for display only and not to be parsed. * * @return The non-null string representation of this reference. */ public String toString() { StringBuilder sb = new StringBuilder("Reference Class Name: " + className + "\n"); int len = addrs.size(); for (int i = 0; i < len; i++) sb.append(get(i).toString()); return sb.toString(); } /** * Makes a copy of this reference using its class name * list of addresses, class factory name and class factory location. * Changes to the newly created copy does not affect this Reference * and vice versa. */ public Object clone() { Reference r = new Reference(className, classFactory, classFactoryLocation); Enumeration<RefAddr> a = getAll(); r.addrs = new Vector<>(); while (a.hasMoreElements()) r.addrs.addElement(a.nextElement()); return r; } /** * Use serialVersionUID from JNDI 1.1.1 for interoperability */ private static final long serialVersionUID = -1673475790065791735L; };