rfc2713.txt

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RFC 2713                Schema for Java Objects             October 1999


   RMI can be supported using different protocols: the Java Remote
   Method Protocol (JRMP) and the Internet Inter-ORB Protocol (IIOP).
   The JRMP is a specialized protocol designed for RMI; the IIOP is the
   standard protocol for communication between CORBA objects [CORBA].
   RMI over IIOP allows Java remote objects to communicate with CORBA
   objects which might be written in a non-Java programming language
   [RMI-IIOP].

2.5.1 Representation in the Directory

   Remote objects that use the IIOP are represented in the directory as
   CORBA object references [CORBA-LDAP].  Remote objects that use the
   JRMP are represented in the directory in one of two ways: as a
   marshalled object, or as a JNDI reference.

   A marshalled object records the codebases of the remote object's stub
   and any serializable or remote objects that it references, and
   replaces remote objects with their stubs.  To store a Remote object
   as a marshalled object (java.rmi.MarshalledObject), you first create
   a java.rmi.MarshalledObject instance for it.

       java.rmi.Remote robj = ...;
       java.rmi.MarshalledObject mobj =
           new java.rmi.MarshalledObject(robj);

   You can then store the MarshalledObject instance as a
   javaMarshalledObject.  The javaClassName attribute should contain the
   fully qualified name of the distinguished class of the remote object.
   The javaClassNames attribute should contain the names of the classes
   and interfaces of the remote object.  To read the remote object back
   from the directory, first deserialize the contents of the
   javaSerializedData to get a MarshalledObject (mobj), then retrieve it
   from the MarshalledObject as follows:

       java.rmi.Remote robj = (java.rmi.Remote)mobj.get();

   This returns the remote stub, which you can then use to invoke remote
   methods.

   MarshalledObject is available only on the Java 2 Platform, Standard
   Edition, v1.2 and higher releases. Therefore, a remote object stored
   as a MarshalledObject can only be read by clients using the the Java
   2 Platform, Standard Edition, v1.2 or higher releases.








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   To store a remote object as a JNDI reference, you first create a
   javax.naming.Reference object instance for it using the remote
   object's string name as it has been, or will be, recorded with the
   RMI registry, with the additional restriction that the "rmi:" prefix
   must be present. Here's an example:

       javax.naming.Reference ref = new javax.naming.Reference(
         obj.getClass().getName(),
         new javax.naming.StringRefAddr("URL",
             "rmi://rserver/AppRemoteObjectX"));

   You then store the javax.naming.Reference instance as a
   javaNamingReference.  The advantage of using a JNDI reference is that
   this can be done without a reference to the remote object. In fact,
   the remote object does not have to exist at the time that this
   recording in the directory is made.  The remote object needs to exist
   and be bound with the RMI registry when the object is looked up from
   the directory.

2.6  Serialized Objects Vs. Marshalled Objects Vs. References

   The object classes defined in this document store different aspects
   of the Java objects.

   A javaSerializedObject or a serializable object stored as a
   javaMarshalledObject represents the object itself, while a
   javaNamingReference or a remote object stored as a
   javaMarshalledObject represents a "pointer" to the object.

   When storing a serializable object in the directory, you have a
   choice of storing it as a javaSerializedObject or a
   javaMarshalledObject.  The javaSerializedObject object class provides
   the basic way in which to store serializable objects. When you create
   an LDAP entry using the javaSerializableObject object class, you must
   explicitly set the javaCodebase attribute if you want readers of that
   entry to know where to load the class definitions of the object. When
   you create an LDAP entry using the javaMarshalledObject object class,
   you use the MarshalledObject class.  The MarshalledObject class uses
   the RMI infrastructure available on the Java platform to automate how
   codebase information is gathered and recorded, thus freeing you from
   having to set the javaCodebase attribute. On the other hand, the
   javaCodebase attribute is human-readable and can be updated easily by
   using text-based tools without having to change other parts of the
   entry.  This allows you, for instance, to move the class definitions
   to another location and then update the javaCodebase attribute to
   reflect the move without having to update the serialized object
   itself.




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   A javaNamingReference provides a way of recording address information
   about an object which itself is not directly stored in the directory.
   A remote object stored as a javaMarshalledObject also records address
   information (the object's "stub") of an object which itself is not
   directory stored in the directory.  In other words, you can think of
   these as compact representations of the information required to
   access the object.

   A javaNamingReference typically consists of a small number of human-
   readable strings.  Standard text-based tools for directory
   administration may therefore be used to add, read, or modify
   reference entries -- if so desired -- quite easily.  Serialized and
   marshalled objects are not intended to be read or manipulated
   directly by humans.

3 Attribute Type Definitions

   The following attribute types are defined in this document:

       javaClassName
       javaClassNames
       javaCodebase
       javaSerializedData
       javaFactory
       javaReferenceAddress
       javaDoc

3.1 javaClassName

   This attribute stores the fully qualified name of the Java object's
   "distinguished" class or interface (for example, "java.lang.String").
   It is a single-valued attribute. This attribute's syntax is '
   Directory String' and its case is significant.

       ( 1.3.6.1.4.1.42.2.27.4.1.6
         NAME 'javaClassName'
         DESC 'Fully qualified name of distinguished Java class or
               interface'
         EQUALITY caseExactMatch
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
         SINGLE-VALUE
       )









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3.2 javaCodebase

   This attribute stores the Java class definition's locations.  It
   specifies the locations from which to load the class definition for
   the class specified by the javaClassName attribute.  Each value of
   the attribute contains an ordered list of URLs, separated by spaces.
   For example, a value of "url1 url2 url3" means that the three
   (possibly interdependent) URLs (url1, url2, and url3) form the
   codebase for loading in the Java class definition.

   If the javaCodebase attribute contains more than one value, each
   value is an independent codebase. That is, there is no relationship
   between the URLs in one value and those in another; each value can be
   viewed as an alternate source for loading the Java class definition.
   See [Java] for information regarding class loading.

   This attribute's syntax is 'IA5 String' and its case is significant.

       ( 1.3.6.1.4.1.42.2.27.4.1.7
         NAME 'javaCodebase'
         DESC 'URL(s) specifying the location of class definition'
         EQUALITY caseExactIA5Match
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
       )

3.3 javaClassNames

   This attribute stores the Java object's fully qualified class or
   interface names (for example, "java.lang.String").  It is a
   multivalued attribute. When more than one value is present, each is
   the name of a class or interface, or ancestor class or interface, of
   this object.

   This attribute's syntax is 'Directory String' and its case is
   significant.

       ( 1.3.6.1.4.1.42.2.27.4.1.13
         NAME 'javaClassNames'
         DESC 'Fully qualified Java class or interface name'
         EQUALITY caseExactMatch
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
       )









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3.4 javaSerializedData

   This attribute stores the serialized form of a Java object.  The
   serialized form is described in [Serial].

   This attribute's syntax is 'Octet String'.

       ( 1.3.6.1.4.1.42.2.27.4.1.8
         NAME 'javaSerializedData
         DESC 'Serialized form of a Java object'
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.40
         SINGLE-VALUE
       )

3.5 javaFactory

   This attribute stores the fully qualified class name of the object
   factory (for example, "com.wiz.jndi.WizObjectFactory") that can be
   used to create an instance of the object identified by the
   javaClassName attribute.

   This attribute's syntax is 'Directory String' and its case is
   significant.

       ( 1.3.6.1.4.1.42.2.27.4.1.10
         NAME 'javaFactory'
         DESC 'Fully qualified Java class name of a JNDI object factory'
         EQUALITY caseExactMatch
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
         SINGLE-VALUE
       )

3.6 javaReferenceAddress

   This attribute represents the sequence of addresses of a JNDI
   reference.  Each of its values represents one address, a Java object
   of type javax.naming.RefAddr.  Its value is a concatenation of the
   address type and address contents, preceded by a sequence number (the
   order of addresses in a JNDI reference is significant).  For example:

       #0#TypeA#ValA
       #1#TypeB#ValB
       #2#TypeC##rO0ABXNyABpq...

   In more detail, the value is encoded as follows:






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   The delimiter is the first character of the value.  For readability
   the character '#' is recommended when it is not otherwise used
   anywhere in the value, but any character may be used subject to
   restrictions given below.

   The first delimiter is followed by the sequence number.  The sequence
   number of an address is its position in the JNDI reference, with the
   first address being numbered 0.  It is represented by its shortest
   string form, in decimal notation.

   The sequence number is followed by a delimiter, then by the address
   type, and then by another delimiter.  If the address is of Java class
   javax.naming.StringRefAddr, then this delimiter is followed by the
   value of the address contents (which is a string).  Otherwise, this
   delimiter is followed immediately by another delimiter, and then by
   the Base64 encoding of the serialized form of the entire address.

   The delimiter may be any character other than a digit or a character
   contained in the address type.  In addition, if the address contents
   is a string, the delimiter may not be the first character of that
   string.

   This attribute's syntax is 'Directory String' and its case is
   significant.  It can contain multiple values.

       ( 1.3.6.1.4.1.42.2.27.4.1.11
         NAME 'javaReferenceAddress'
         DESC 'Addresses associated with a JNDI Reference'
         EQUALITY caseExactMatch
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
       )

3.7 javaDoc

   This attribute stores a pointer to the Java documentation for the
   class.  It's value is a URL. For example, the following URL points to
   the specification of the java.lang.String class:
   http://java.sun.com/products/jdk/1.2/docs/api/java/lang/String.html

   This attribute's syntax is 'IA5 String' and its case is significant.

       ( 1.3.6.1.4.1.42.2.27.4.1.12
         NAME 'javaDoc'
         DESC 'The Java documentation for the class'
         EQUALITY caseExactIA5Match
         SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
       )




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4 Object Class Definitions

   The following object classes are defined in this document:

       javaContainer
       javaObject
       javaSerializedObject
       javaMarshalledObject
       javaNamingReference

4.1 javaContainer

   This structural object class represents a container for a Java
   object.

       ( 1.3.6.1.4.1.42.2.27.4.2.1
         NAME 'javaContainer'
         DESC 'Container for a Java object'
         SUP top
         STRUCTURAL
         MUST ( cn )
       )

4.2 javaObject

   This abstract object class represents a Java object.  A javaObject
   cannot exist in the directory; only auxiliary or structural
   subclasses of it can exist in the directory.

       ( 1.3.6.1.4.1.42.2.27.4.2.4
         NAME 'javaObject'
         DESC 'Java object representation'
         SUP top
         ABSTRACT
         MUST ( javaClassName )
         MAY ( javaClassNames $
               javaCodebase $
               javaDoc $
               description )
       )











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