Chapter5.Distributed Objects

Chapter 5. Distributed Objects

• The Roles of Client and Server

• Remote Method Invocations

• Setup for Remote Method Invocation

• Parameter Passing in Remote Methods

• Server Object Activation

• Java IDL and CORBA

• Remote Method Calls with SOAP

Periodically, the programming community starts thinking of "objects everywhere" as the solution to all its problems. The idea is to have a happy family of collaborating objects that can be located anywhere. These objects are, of course, supposed to communicate through standard protocols across a network. For example, you'll have an object on the client where the user can fill in a request for data. The client object sends a message to an object on the server that contains the details of the request. The server object gathers the requested information, perhaps by accessing a database or by communicating with additional objects. Once the server object has the answer to the client request, it sends the answer back to the client. Like most bandwagons in programming, this plan contains a fair amount of hype that can obscure the utility of the concept. This chapter

• Explains the models that make interobject communication possible;

• Explains situations in which distributed objects can be useful;

• Shows you how to use remote objects and the associated remote method invocation (RMI) for communicating between two Java virtual machines (which may run on different computers); and

• Introduces you to CORBA and SOAP, technologies that allow communication between objects that are written in different programming languages.