Reading Objects from the Directory
Lists
The Naming Operations lesson showed you how to list a context using the Context.list() and Context.listBindings() methods. This section describes how these methods are affected by object factories.
List When you use Context.list(), you get back an enumeration of NameClassPair. You can invoke getClassName() on each NameClassPair to obtain the class name of the object in that binding.
For example, if you list the context that you used to bind the various objects in the Storing Objects in the Directory lesson, then you get the following output.
For each binding, the Java class name was determined based on information stored in the directory, without an instance of the object in the binding necessarily having to be created. No object factory was involved.# java List ou=Groups: javax.naming.directory.DirContext ou=People: javax.naming.directory.DirContext cn=Button: java.awt.Button cn=Flower: Flower cn=favorite: Fruit cn=favDrink: javax.naming.directory.DirContext cn=RefHello: Hello cn=CorbaHello: javax.naming.directory.DirContext cn=RmiiiopHello: javax.naming.directory.DirContext cn=RemoteHello: HelloImpl
List Bindings When you use Context.listBindings(), you get back an enumeration of Binding. You can invoke getObject() on each Binding to obtain the object in that binding. The result of getObject() is the same as that obtained by looking up the object by using Context.lookup().
For example, if you list the bindings in the context that you used to bind the various objects in the Storing Objects in the Directory lesson, then you get the following output.
Notice that the "cn=favDrink" entry and a few others now have a more precise class name ("Drink", "HelloImpl_Stub"). This is because instantiating the object (by the corresponding object factory) provided more class information. Notice also that the remote object HelloImpl was returned as a stub to the real object.# java -Djava.security.manager -Djava.security.policy=.policy ListBindings ou=Groups: com.sun.jndi.ldap.LdapCtx: com.sun.jndi.ldap.LdapCtx@1dacd730 ou=People: com.sun.jndi.ldap.LdapCtx: com.sun.jndi.ldap.LdapCtx@1dacd8ae cn=Button: java.awt.Button: java.awt.Button[button0,0,0,0x0,invalid,label=Push me] cn=Flower: Flower: pink rose cn=favorite: Fruit: orange cn=favDrink: Drink: water cn=RemoteHello: HelloImpl_Stub: HelloImpl_Stub[RemoteStub [ref: [endpoint:[129.111.111.111:44999](remote),objID:[-68dff7b3:d975735a08:-8000, 0]]]] cn=RefHello: HelloImpl_Stub: HelloImpl_Stub[RemoteStub [ref: [endpoint:[129.111.111.111:45006](remote),objID:[2bf4308e:d975745b44:-8000, 0]]]] cn=CorbaHello: com.sun.CORBA.idl.CORBAObjectImpl: com.sun.CORBA.idl.CORBAObjectImpl:com.sun.CORBA.idl.GenericCORBAClientSC@84675dd2 cn=RmiiiopHello: com.sun.CORBA.idl.CORBAObjectImpl: com.sun.CORBA.idl.CORBAObjectImpl:com.sun.CORBA.idl.GenericCORBAClientSC@ac6b5dd2
Note 1: You must run this example by using the Java 2 Platform, v1.2, or higher release because some of the object factories require that platform.Note 2: The -Djava.security.manager option specifies that the default security manager be used, and the -Djava.security.policy=.policy option specifies that the .policy file be used for the security policy. These two options are needed when you are listing/looking up the java.rmi.Remote objects. In the policy file, you need to grant permission to connect to and accept connections from the Web server and the machine on which the remote objects are running.
Reading Objects from the Directory