Three mainstream technologies for distributed objects--com, Java, and Cobra

Both last time, see there is again about the object, distributed objects, so excerpt into the following:

At present, there are three major schools of distributed object Technology--cobra, com/dcom and Java in the world. CORBA technology was the first, 1991 OMG issued the Cobra 1.0 standard, at that time did very beautiful; Then there is the Microsoft COM series, from the original COM to the current DCOM, the formation of a Microsoft set of distributed object computing platform , while Sun's Java platform, at the time of its earliest launch, provided only remote method calls, which at that time could not be called distributed object computing, but belonged to a network computing, and then launched the JavaBean, is not enough to contend with the above two schools, and its current version is called the Java EE, The introduction of EJB, in addition to the language also has the components of the standard and the framework of working together communication between components. So, it has formed the current three major schools.

----should say, among the three, the Cobra standard is the most beautiful. The Cobra standard is divided into 3 levels: Object request agent, public object service and public facility. At the bottom is the object request Proxy Orb, which defines the definition (interface) and language mapping of the distributed object, realizes the communication and interoperation between objects, is the "soft bus" in the Distributed object system, and defines many public services on the Orb, which can provide such as concurrent service, Name service, transaction (transaction) service, Services such as security services; The top-level utility defines the component framework, provides services that can be used directly for business objects, and defines the contract rules that are required for the business objects to collaborate effectively. In short, CORBA is characterized by chatty, interoperability and openness are very good. Currently, the latest version of CORBA is 2.3. CORBA 3.0 has also been largely completed, adding content such as Internet integration and QoS control. The drawbacks of CORBA are large and complex, and the technology and standard updates are relatively slow, and the Cobra specification has a very short time to upgrade from 1.0 to 2.0, and the release of the previous version is relatively slow.

----In contrast, Java standards are much faster, and Java is the company's own, evolving quickly. Java has the advantage of being a language-friendly, cross-platform. Java distributed object Technology typically refers to remote method invocation (RMI) and enterprise-level JavaBean (EJB). RMI provides a way for a Java object to remotely invoke another Java object, similar to a traditional RPC, and can only support primary distributed object interoperation. Sun was based on RMI and proposed EJB. Based on the Java server-side component model, the EJB framework provides services such as remote access, security, transaction, persistence, and life-cycle management to support distributed object computing. At present, Java Technology and CORBA technology have converged trend.

----COM technology was made exclusively by Microsoft, and was developed in Windows 3.1 with OLE technology to support composite documents, through several stages of OLE 2/com, ActiveX, DCOM, and COM +, currently COM + The message communication module MSMQ and the transaction module to solve the key business MTS are added, which is a relatively complete platform for distributed object calculation. Microsoft's COM platform is more efficient, and it has a range of development tools to support it, and application development is relatively straightforward. But it has a fatal weakness is that COM's cross-platform is poor, how to achieve interoperability with third-party vendors is always a big problem. From the point of view of the development of distributed object technology, most people think that COM competes for Cobra.

Three mainstream technologies for distributed objects--com, Java, and Cobra