EJB, Spring Remoting, and Web Services - Spring Enterprise Recipes: A Problem Solution Approach - page 199

C H A P T E R 5
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EJB, Spring Remoting, and Web
Services
In this chapter, you will learn about Spring's support for various remoting technologies, such as EJB,
RMI, Hessian, Burlap, HTTP Invoker, and Web Services. Remoting is a key technology in developing
distributed applications, especially multitier enterprise applications. It allows different applications or
components, running in different JVMs or on different machines, to communicate with each other using
a specific protocol.
Spring's remoting support is consistent across different remoting technologies. On the server side,
Spring allows you to expose an arbitrary bean as a remote service through a service exporter. On the
client side, Spring provides various proxy factory beans for you to create a local proxy for a remote
service so that you can use the remote service as if it were a local bean.
Nowadays, there are two main approaches to developing web services: contract-first and contract-
last . Automatically exposing a bean from the IoC container as a web service means that the service is
contract-last because the service contract is generated from an existing bean. The Spring team has
created a subproject called Spring Web Services (Spring-WS), which focuses on the development of
contract-first web services. In this approach, a service contract is defined first, and code is then written
to fulfill this contract.
5-1. Exposing and Invoking Services Through RMI
Problem
You want to expose a service from your Java application for other Java-based clients to invoke remotely.
Because both parties are running on the Java platform, you can choose a pure Java-based solution
without considering cross-platform portability.
Solution
Remote Method Invocation (RMI) is a Java-based remoting technology that allows two Java applications
running in different JVMs to communicate with each other. With RMI, an object can invoke the methods
of a remote object. RMI relies on object serialization to marshal and unmarshal method arguments and
return values.