According to Wikipedia, Hessian is a binary web service protocol that makes web services usable without requiring a large framework, and without learning a new set of protocols. Because it is a binary protocol, it is well-suited to sending binary data without any need to extend the protocol with attachments.

From what i’ve tested, perhaps it is somekind of light version of remote EJB3 because i dont have to include so many libraries like EJB3. Altough EJB3 and Hessian are not apple-to-apple comparable, because both arent using the same messaging protocol. EJB3 use RMI-IIOP while Hessian use WebService.

So let’s start with the code. First, for the server part (im using tomcat), create a web project on Netbeans 6.9 and creating a simple interface class,

package com.edw.service;

public interface HelloService {
    String sayHelloTo(String target);
}

after that, i create a simple servlet which implements HelloService interface,

package com.edw.servlet;

import com.caucho.hessian.server.HessianServlet;
import com.edw.service.HelloService;

public class HelloServlet extends HessianServlet implements HelloService {

    public String sayHelloTo(String target) {
        return "hello "+target+", have a nice day";
    }
    
}

dont forget to register your servlet to web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>HelloServlet</servlet-name>
        <servlet-class>com.edw.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloServlet</servlet-name>
        <url-pattern>/HelloServlet</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

next, is creating the client application. I start with a simple java netbeans project, a main class and an interface, i copied the exact copy of HelloService and then put it on my client project,

package com.edw.service;

public interface HelloService {
    String sayHelloTo(String target);
}

and my main class

package com.edw.main;

import com.caucho.hessian.client.HessianProxyFactory;
import com.edw.service.HelloService;

public class Main {

    String url = "http://localhost:809/HessianServer/HelloServlet";
    HessianProxyFactory factory = new HessianProxyFactory();

    public Main() {
    }

    private void doTest() {
        try {
            HelloService hello = (HelloService) factory.create(HelloService.class, url);
            System.out.println(hello.sayHelloTo("si pepe"));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Main main = new Main();
        main.doTest();
    }
}

here is the screenshot of my project

This is what the messaging looks like

another good competitor for Spring Http Invoker.
Have fun