Hessian Service Example

Hessian Service

Writing a Hessian service as a plain-old Java object (POJO) eliminates protocol dependencies and simplifies service testing.

The [../hessian-add/ addition example] built the Hessian service as an extension of HessianService for simplicity. Most services will want to be independent of the Hessian protocol itself.

Files in this tutorial

File	Description
WEB-INF/classes/example/MathService.java	Interface for the math service.
WEB-INF/classes/example/MathServiceImpl.java	The main service implementation.
WEB-INF/resin-web.xml	Configures the environment
demo.jsp	Client JSP
demo.php	Client PHP

Service Implementation

The MathService implementation is just a Java class that implements the MatchService API.

Example: MathServiceImpl.java

package example;

public class MathServiceImpl implements MathService {
  public int add(int a, int b)
  {
    return a + b;
  }
}

Remote Interface

The Java interface describes the remote API. This example has an addition method, add().

Resin's proxy client implementation uses the remote interface to expose the API to the proxy stub. Strictly speaking, though, the Java remote interface is not required for Hessian. A non-Java client will not use the Java interface, except possibly as documentation.

Example: MathService.java

package example;

public interface MathService {
  public int add(int a, int b);
}

Service configuration

Example: resin-web.xml

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

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

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

</web-app>

Java Client

The client is identical to the basic example.

Example: demo.jsp

<%@ page import="javax.webbeans.In" %>
<%@ page import="example.MathService" %>
<%!
@In MathService math;
%>
<pre>
3 + 2 = <%= math.add(3, 2) %>
3 - 2 = <%= math.sub(3, 2) %>
3 * 2 = <%= math.mul(3, 2) %>
3 / 2 = <%= math.div(3, 2) %>
</pre>

results

3 + 2 = 5
3 - 2 = 1
3 * 2 = 6
3 / 2 = 1

PHP Client

The client is identical to the basic example.

Example: demo.php

<?php

$math = java_bean("math");
?>
<pre>
3 + 2 = <?= $math->add(3, 2) ?>
3 - 2 = <?= $math->sub(3, 2) ?>
3 * 2 = <?= $math->mul(3, 2) ?>
3 / 2 = <?= $math->div(3, 2) ?>
</pre>

results

3 + 2 = 5
3 - 2 = 1
3 * 2 = 6
3 / 2 = 1