
Comparison
The new CORBA2 specification defines interoperable networked objects.
The earlier CORBA1 lacks interoperability between vendors. The interoperable
profile of CORBA2 is called IIOP, Internet Inter-Object Protocol. This
protocol is mandatory to comply CORBA2. Sun announced that they would bandle
a CORBA class library to JDK 1.1. The class library includes the client
part. The server side will be sold by Sun as Joe. Joe runs on Solaris NEO.
- CORBA is neutral and interoperable to languages and machine architectures,
while HORB is dedicated to Java. HORB is, however, optimized to Java.
- CORBA2 cannot pass objects.
- Since CORBA is language independent, you need to write the interface
of objects in the OMG IDL language in addition to the real code. IDL's
object model has nothing to do with language's object model. In HORB, a
Java object becomes a remote object.
- CORBA CORE provides basic functionality for object communication. It
does not support object passing. Other services, such as persistence, composite
document and transaction, are defined in CORBA Services and are options.
In case of HORB it lacks such services. But you can use many utilities
written for Java.
ILU of Xerox is a free implementation of CORBA and it will support Java.
Java RMI (Remote Method Invocation) was announced in March by Sun. RMI
provides basic functionality for remote method invocation. The features
and the implementation tequnique are near to an earlier versin of HORB.
Sun will bandle an RMI class library to JDK 1.1. The class library includes
client part. Server side will be sold by Sun.
- On RMI, you can connect to existing remote objects. HORB supports connecting
to existing remote objects and creation of remote objects. Remote object
creation provides private data storage to each client, and it makes programming
easy.
- RMI supports dynamic stub loading which downloads stub classes from
servers on demand. HORB will support it.
- RMI can pass private variables when an object is passed, and RMI does
not need to have stub classes for objects that are passed. That is because
it utilizes the builtin object serializer that was newly equiped in the
Java Virtual Machine. HORB will also support the builtin object serializer
so that it can pass object without making proxy classes.
- Distributed Access Control List of HORB provides an eash mechanism
to control accesses to objects. You can limit accesses from certain hosts
and/or users to each class or method.
- HORB has many features (the current) RMI lacks, such as asynchronous
method invocation, invitation, distributed access control list and so on.
You can obtain a beta version of RMI from the homepage of Javasoft.
Microsoft has announced thier new Java development environment will
support OLE development in Java. Network programmin is supported by Active
X Control for Internet. It includes Active X Controls (OLE controls) for
STMP, HTTP, socket and so on.
Windows NT 4.0 Beta2 includes DCOM (Distributed Component Object Model),
and the Visual Basic 4.0 The enterprise version supports Remote OLE.