Resin : Development Guide : A Simple Service for Resin Remoting

Writing a service for the Resin remoting as a plain-old Java object (POJO) eliminates protocol dependencies and simplifies service testing.

With the Resin remoting, services can be written as plain-old Java objects (POJOs) and made available to many different protocols using simple configuration changes.

The Resin remoting is an infrastructure that allows a service to be exposed via many different service protocols. For example in this tutorial, there is a plain-old Java object (POJO) that implements a service and this service is made available using REST, SOAP, Hessian, and WebBeans. The service is implemented once and these protocols are activated with a few simple changes to the configuration file.

In this example, the service interface is for a simple Hello, World service. There is a single method, hello() that the service must implement and the client may invoke.

HelloService.java

package example;

public interface HelloService {
  /**
   * Returns "hello, world".
   */
  public String hello();
}

The HelloService implementation is just a Java class that implements the HelloService API. It can optionally use EJB annotations like @Remote, @Stateless or @TransactionAttribute.

HelloServiceImpl.java

package example;

public class HelloServiceImpl implements HelloService {
  /**
   * Returns "hello, world".
   */
  public String hello()
  {
    return "hello, world";
  }
}

Services for Resin remoting are configured with the <servlet> tag. The implementation class is given as the servlet-class attribute. It is possible to allow access to the service within the same virtual machine by registering the service as a WebBeans singleton with <bean>.

To expose the service as a Hessian service, use the <hessian> tag. Hessian is one of the protocols available for web services.

remoting service for hessian

<web-app xmlns="http://caucho.com/ns/resin">

  <servlet-mapping url-pattern="/hello/hessian/*"
                   servlet-class="example.HelloServiceImpl">
    <protocol uri="hessian:"/>
  </servlet-mapping>

</web-app>

remote service for CXF

<web-app xmlns="http://caucho.com/ns/resin">

  <servlet-mapping url-pattern="/hello/hessian/*"
                   servlet-class="example.HelloServiceImpl">
    <protocol uri="cxf:"/>
  </servlet-mapping>

</web-app>

service as WebBeans singleton

<web-app xmlns="http://caucho.com/ns/resin">

  <bean class="example.HelloServiceImpl" name="vm"/>

</web-app>

Resin also makes it easy to access services using the <remote-client> tag. This tag connects to a service using a URI of the form <protocol>:url=<location>. The example below shows just such a URL. The interface of the service is required. The <remote-client> tag creates a proxy client instance for the service and registers the proxy with WebBeans.

<remote-client>

<web-app xmlns="http://caucho.com/ns/resin">

  <remote-client interface="example.HelloService" name="hessian">
    <uri>hessian:url=${webApp.url}/hello/hessian/</uri>
  </remote-client>  

  <remote-client interface="example.HelloService" name="rest">
    <uri>rest:url=${webApp.url}/hello/rest/</uri>
  </web-service-client>

  <remote-client interface="example.HelloService" name="soap">
      <uri>xfire:url=${webApp.url}/hello/soap/</url>
  </remote-client>

</web-app>

The client can now connect to the HelloService using any supported encoding simply by doing a WebBeans injection.

demo.jsp

<%@ page import="javax.webbeans.Named" %>
<%@ page import="example.HelloService" %>
<%!
@Named("hessian") HelloService _hessianHello;
@Named("rest") HelloService _restHello;
@Named("soap") HelloService _soapHello;
@Named("vm") HelloService _vmHello;
%>
<pre>
From Hessian: <%= _hessianHello.hello() %>
From REST: <%= _restHello.hello() %>
From SOAP: <%= _soapHello.hello() %>
From VM: <%= _vmHello.hello() %>
</pre>

From Hessian: hello, world
From REST: hello, world
From SOAP: hello, world
From VM: hello, world

The client can now connect to the HelloService using PHP with the java_bean() method.

demo.php

<?php
$hessian = java_bean("hessian");
$rest = java_bean("rest");
$soap = java_bean("soap");
$vm = java_bean("vm");
?>
<pre>
From Hessian: <?= $hessian->hello() ?>
From REST: <?= $rest->hello() ?>
From SOAP: <?= $soap->hello() ?>
From VM: <?= $vm->hello() ?>
</pre>

From Hessian: hello, world
From REST: hello, world
From SOAP: hello, world
From VM: hello, world

a simple service for resin remoting

See Also

Files in this tutorial

Introduction

Service Interface

Service Implementation

Service configuration

Client configuration

JSP Client Script

PHP Client Script