java code

package test.dwr.it;

public class MyClass {
public String say(String wath) {
return “say: ” + wath;
}
}

spring bean configuration file or dwr.xml configuration file

<bean id=”myClass” class=”test.dwr.it.MyClass”>
<dwr:remote javascript=”myClassRemoted” />
</bean>

web.xml

<servlet>
  <servlet-name>dwr-invoker</servlet-name>
  <display-name>DWR Servlet</display-name>
  <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
</servlet>

<servlet-mapping>
  <servlet-name>dwr-invoker</servlet-name>
  <url-pattern>/dwr/*</url-pattern>
</servlet-mapping>

jsp

<script src='/[YOUR-WEBAPP]/dwr/interface/myClassRemoted.js'></script>
<script src='/[YOUR-WEBAPP]/dwr/engine.js'></script>

<script type="text/javascript">

  myClassRemoted.say('Hello',handleGetData);

  function handleGetData(data) {

    alert(data);

  }

</script>

put drw.jar in your classpath and...
result is javascritp alert with string value: "say: Hello".

more info @:

http://directwebremoting.org/dwr/overview/dwr