Resin : Tutorials : A frontend client for a Hessian service

A frontend client for a Hessian service

Resin 3.1

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This tutorial shows how to access services with Resin WebBeans injection. A servlet does frontend presentation for the results of a Hessian web service.

Demo

Files in this tutorial

WEB-INF/classes/example/HelloService.java	Interface for the hello service.
WEB-INF/classes/example/HelloServiceImpl.java
WEB-INF/classes/example/ServiceFrontendServlet.java	The main service implementation.
WEB-INF/resin-web.xml	Configures the environment
demo.jsp	Client JSP

Service Interface and Configuration

The service used in this example is the same hello world service used in the simple service tutorial. The interface used by the frontend is shown below.

HelloService.java

package example;

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

Configuring the service is also the same as in the the simple service tutorial.

<servlet>

<servlet-mapping url-pattern="/hello/*"
                 servlet-class="example.HelloServiceImpl"
                 jndi-name="service/HelloService">

  <protocol type="hessian"/>
</servlet-mapping>

Frontend Client

The client in this case is simply a servlet that uses J2EE injection to access the service.

ServiceFrontendServlet.java

package example;

import java.io.*;
import javax.annotation.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ServiceFrontendServlet extends HttpServlet {
  @Resource(name="hessian/HelloService")
  private HelloService _helloService;

  public void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws IOException, ServletException
  {
    PrintStream out = new PrintStream(resp.getOutputStream());

    out.println("service result: " + _helloService.hello());
  }
}

Configuring the client is nearly the same as in the the simple service tutorial, the only difference being adding the mapping for the servlet.

Client configuration

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

<servlet servlet-name="service-frontend" 
         servlet-class="example.ServiceFrontendServlet" />
<servlet-mapping url-pattern="/frontend/" servlet-name="service-frontend" />