10.4.2 Looking up the Connector Servers with the JNDI/LDAP Lookup Service

The following code extract is taken from the Client class in the Jini Lookup Service examples directory.

Example 10–13 Looking up the Connector Servers with the JNDI/LDAP Lookup Service

[...] 
 
public class Client { 
 
   private static boolean debug = false; 
 
   public static void listAttributes(DirContext root, String dn) 
     throws NamingException { 
     final Attributes attrs = root.getAttributes(dn); 
     System.out.println("dn: " + dn); 
     System.out.println("attributes: " + attrs); 
   } 
    
   public static DirContext getRootContext() throws NamingException { 
      final Hashtable env = new Hashtable(); 
      // Prepare environment map 
      [...] 
       
      InitialContext root = new InitialLdapContext(env,null); 
      return (DirContext)(root.lookup("")); 
   } 
    
   // Confirm URL has not expired  
  [...]  
 
   public static List lookup(DirContext root, String protocolType, 
                             String name) 
      throws IOException, NamingException { 
      final ArrayList list = new ArrayList(); 
      String queryProtocol = 
         (protocolType==null)?"":"(jmxProtocolType="+protocolType+")"; 
      String query = 
          "(&" + "(objectClass=jmxConnector) " + 
          "(jmxServiceURL=*) " + 
          queryProtocol + 
          "(jmxAgentName=" + ((name!=null)?name:"*") + "))"; 
 
      SearchControls ctrls = new SearchControls(); 
      ctrls.setSearchScope(SearchControls.SUBTREE_SCOPE); 
      final NamingEnumeration results = root.search("", query, ctrls); 
      while (results.hasMore()) {  
           final SearchResult r = (SearchResult) results.nextElement(); 
           debug("Found node: " + r.getName()); 
           final Attributes attrs = r.getAttributes(); 
           final Attribute attr = attrs.get("jmxServiceURL"); 
           if (attr == null) continue; 
           final Attribute exp = attrs.get("jmxExpirationDate"); 
           if ((exp != null) && hasExpired((String)exp.get())) { 
               System.out.print(r.getName() + ": "); 
               System.out.println("URL expired since: " + exp.get()); 
               continue; 
           }   
           final String urlStr = (String)attr.get(); 
           if (urlStr.length() == 0) continue; 
 
    
           debug("Found URL: "+ urlStr); 
 
    
           final JMXServiceURL url = new JMXServiceURL(urlStr); 
           final JMXConnector conn = 
               JMXConnectorFactory.newJMXConnector(url,null); 
           list.add(conn); 
           if (debug) listAttributes(root,r.getName()); 
      } 
 
      return list; 
 
   }   
} 
 

In Example 10–13, the Client firstly returns a pointer root to the LDAP directory DirContext, then it searches through the directory for object classes of the type jmxConnector. The service URL and expiry date attributes, attr and exp respectively, for the jmxConnector object classes are obtained, exp is checked to make sure that the URL has not expired and a call is made to JMXConnectorFactory to create a new connector conn. The connector conn is added to the list of connectors and is used to access the MBeans in the MBean server created by Server.