Spring Tutorials

Spring provides various ways to develop remote services. Remote services are services hosted on remote servers and accessed by clients over the network. For example, lets say you are developing a desktop application that needs to connect to a central server. The desktop application can be on various machines. you can use spring remoting to connect the clients on the desktop to the server.

Web services developed using JAX-WS can also be developed and integrated using Spring. Currently, Spring supports the following remoting technologies:

1. RMI- Remote Method Invocation - Use RMI to invoke a remote method. The java objects are serialized.
2. Hessian- Transfer binary data between the client and the server.
3. Burlap- Transfer XML data between the client and the server. It is the XML alternative to Hessian.
4. JAX-WS- Java XML API for Web Services.
5. Spring’s HTTP invoker- Spring provides a special remoting strategy which allows for Java serialization via HTTP, supporting any Java interface . The corresponding support classes are HttpInvokerProxyFactoryBean and HttpInvokerServiceExporter.
6. JMS- Remoting using JMS as the underlying protocol is supported via the JmsInvokerServiceExporter and JmsInvokerProxyFactoryBean classes.
7. AMQP- Remoting using AMQP as the underlying protocol is supported by the Spring AMQP project.

In this Topic we provide the Spring Remoting using RMI with workflow. Spring creates a proxy that represents the actual remote bean. The proxy is created using RmiProxyFactoryBean. The proxy can be used as a normal Spring bean and the client code does not need to know that it is actually calling a remote method.

The important classes org.springframework.aop.framework.ProxyFactory.RmiProxyFactoryBean. This class will be used by the client to create a proxy to connect to the remote service. This is a spring FactoryBean for creating RMI proxies. The proxied service is use a spring bean using the interface specified in the ServiceInterface property.

The Remote service URL can be specified by the serviceUrl property. org.springframework.remoting.rmi.RmiServiceExporter - This class will be used by the server to create a remote service. below diagram shows the process of RMI.

There are following steps to explain the diagram as follows:

1. Client sends a message call.
2. This message call is handled by an RMI Proxy created by RmiProxyFactoryBean.
3. The RMI Proxy converts the call into a remote call over JRMP (Java Remote Method Protocol).
4. The RMI Service Adapter created by RmiServiceExporter intercepts the remote call over JRMP.
5. It forwards the method call to Service.