LinkRef


1   /*
2    * @(#)LinkRef.java 1.7 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.naming;
9   
10  /**
11    * This class represents a Reference whose contents is a name, called the link name,
12    * that is bound to an atomic name in a context. 
13    *<p>
14    * The name is a URL, or a name to be resolved relative to the initial
15    * context, or if the first character of the name is ".", the name
16    * is relative to the context in which the link is bound.
17    *<p>
18    * Normal resolution of names in context operations always follow links.
19    * Resolution of the link name itself may cause resolution to pass through
20    * other  links. This gives rise to the possibility of a cycle of links whose
21    * resolution could not terminate normally. As a simple means to avoid such
22    * non-terminating resolutions, service providers may define limits on the
23    * number of links that may be involved in any single operation invoked
24    * by the caller.
25    *<p>
26    * A LinkRef contains a single StringRefAddr, whose type is "LinkAddress",
27    * and whose contents is the link name. The class name field of the
28    * Reference is that of this (LinkRef) class.
29    *<p>
30    * LinkRef is bound to a name using the normal Context.bind()/rebind(), and
31    * DirContext.bind()/rebind(). Context.lookupLink() is used to retrieve the link
32    * itself if the terminal atomic name is bound to a link.
33    *<p>
34    * Many naming systems support a native notion of link that may be used
35    * within the naming system itself. JNDI does not specify whether
36    * there is any relationship between such native links and JNDI links.
37    *<p>
38    * A LinkRef instance is not synchronized against concurrent access by multiple
39    * threads. Threads that need to access a LinkRef instance concurrently should
40    * synchronize amongst themselves and provide the necessary locking.
41    *
42    * @author Rosanna Lee
43    * @author Scott Seligman
44    * @version 1.7 03/12/19
45    *
46    * @see LinkException
47    * @see LinkLoopException
48    * @see MalformedLinkException
49    * @see Context#lookupLink
50    * @since 1.3
51    */
52  
53    /*<p>
54    * The serialized form of a LinkRef object consists of the serialized
55    * fields of its Reference superclass.
56    */
57  
58  public class LinkRef extends Reference   {
59      /* code for link handling */
60      static final String   linkClassName = LinkRef  .class.getName();
61      static final String   linkAddrType = "LinkAddress";
62  
63      /**
64        * Constructs a LinkRef for a name.
65        * @param linkName The non-null name for which to create this link.
66        */
67      public LinkRef(Name   linkName) {
68      super(linkClassName, new StringRefAddr  (linkAddrType, linkName.toString()));
69      }
70  
71      /**
72        * Constructs a LinkRef for a string name.
73        * @param linkName The non-null name for which to create this link.
74        */
75      public LinkRef(String   linkName) {
76      super(linkClassName, new StringRefAddr  (linkAddrType, linkName));
77      }
78  
79      /**
80        * Retrieves the name of this link.
81        * 
82        * @return The non-null name of this link.
83        * @exception MalformedLinkException If a link name could not be extracted
84        * @exception NamingException If a naming exception was encountered.
85        */
86      public String   getLinkName() throws NamingException   {
87      if (className != null && className.equals(linkClassName)) {
88          RefAddr   addr = get(linkAddrType);
89          if (addr != null && addr instanceof StringRefAddr  ) {
90          return (String  )((StringRefAddr  )addr).getContent();
91          }
92      }
93      throw new MalformedLinkException  ();
94      }
95      /**
96       * Use serialVersionUID from JNDI 1.1.1 for interoperability
97       */
98      private static final long serialVersionUID = -5386290613498931298L;
99  }
100
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