Before you can use it in FB4 you need to download BlazeDS 4 ( Binary Distribution ) and Adobe LifeCycle Data Services ( you only need the flex-rds-lcds.jar ) Add these jars to the WEB-INF/lib folder and provide the BlazeDS configuration files. It will look like this..
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
id="WebApp_ID" version="2.5">
<display-name>FlashBuilderWeb</display-name>
<servlet>
<servlet-name>MessageBrokerServlet</servlet-name>
<servlet-class>flex.messaging.MessageBrokerServlet</servlet-class>
<init-param>
<param-name>services.configuration.file</param-name>
<param-value>/WEB-INF/flex/services-config.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>RDSDispatchServlet</servlet-name>
<servlet-class>flex.rds.server.servlet.FrontEndServlet</servlet-class>
<init-param>
<param-name>useAppserverSecurity</param-name>
<param-value>false</param-value>
</init-param>
<load-on-startup>10</load-on-startup>
</servlet>
<servlet-mapping id="RDS_DISPATCH_MAPPING">
<servlet-name>RDSDispatchServlet</servlet-name>
<url-pattern>/CFIDE/main/ide.cfm</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>MessageBrokerServlet</servlet-name>
<url-pattern>/messagebroker/*</url-pattern>
</servlet-mapping>
<listener>
<listener-class>flex.messaging.HttpFlexSession</listener-class>
</listener>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
</web-app>
As a demo I created simple getCities JAX-WS service and added this as a destination in the proxy-config.xml of BlazeDS.
package nl.whitehorses.ws;
import java.util.ArrayList;
import java.util.List;
import javax.jws.WebMethod;
import javax.jws.WebParam;
import javax.jws.WebService;
import javax.jws.WebResult;
@WebService(name = "CitiesService",
serviceName = "CitiesService",
portName = "CitiesServicePort")
public class Cities {
public Cities() {
}
@WebMethod
@WebResult(name = "result")
public List<City> getCities( @WebParam(name = "countryCode" ) String countryCode) {
List<City> result = new ArrayList<City>();
if ( countryCode.equalsIgnoreCase("nl") ) {
City c = new City();
c.setCountry("NL");
c.setName("PUTTEN");
result.add(c);
City c2 = new City();
c2.setCountry("NL");
c2.setName("AMSTERDAM");
result.add(c2);
} else if ( countryCode.equalsIgnoreCase("de") ) {
City c = new City();
c.setCountry("DE");
c.setName("BERLIN");
result.add(c);
City c2 = new City();
c2.setCountry("DE");
c2.setName("FRANKFURT");
result.add(c2);
} else {
City c = new City();
c.setCountry(countryCode);
c.setName("NOT FOUND");
result.add(c);
}
return result;
}
}
package nl.whitehorses.ws;
public class City {
private String name;
private String country;
public City() {
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setCountry(String country) {
this.country = country;
}
public String getCountry() {
return country;
}
}
Now it is time to do some work in Flash Builder 4. Go to the Data menu and select in this case Connect to Web Service. This works the same for a Remote Object 
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
xmlns:wscities="services.wscities.*">
<s:applicationComplete>
<![CDATA[
initApp();
]]>
</s:applicationComplete>
<fx:Script>
<![CDATA[
import mx.controls.Alert;
public function initApp():void
{
getCities(country.selectedItem.data);
}
protected function getCities(countryCode:String):void
{
getCitiesResult.token = wsCities.getCities(countryCode);
}
private function changeComboBoxEvt(e:Event):void {
getCities(e.currentTarget.selectedItem.data);
}
]]>
</fx:Script>
<fx:Declarations>
<s:CallResponder id="getCitiesResult"/>
<wscities:WsCities id="wsCities" fault="Alert.show(event.fault.faultString +
'\n' + event.fault.faultDetail)" showBusyCursor="true"/>
</fx:Declarations>
<s:Panel title="RDC with FB4 & BlazeDS">
<s:VGroup>
<mx:ComboBox id="country" width="150" change="changeComboBoxEvt(event)">
<mx:ArrayList>
<fx:Object label="Netherlands" data="NL"/>
<fx:Object label="Germany" data="DE"/>
</mx:ArrayList>
</mx:ComboBox>
<mx:DataGrid x="53" y="36" id="dataGrid" dataProvider="{getCitiesResult.lastResult}">
<mx:columns>
<mx:DataGridColumn headerText="country" dataField="country"/>
<mx:DataGridColumn headerText="name" dataField="name"/>
</mx:columns>
</mx:DataGrid>
</s:VGroup>
</s:Panel>
</s:Application>
If you don't like these mouse clicks you can always do it manually in actionscript.<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
xmlns:wscities="services.wscities.*">
<s:applicationComplete>
<![CDATA[
initApp();
]]>
</s:applicationComplete>
<fx:Script>
<![CDATA[
import mx.controls.Alert;
import mx.events.FlexEvent;
import mx.rpc.AsyncToken;
import mx.rpc.events.FaultEvent;
import mx.rpc.events.ResultEvent;
import services.wscities.WsCities;
public var ws:WsCities;
public function initApp():void
{
ws = new WsCities();
var token:AsyncToken = ws.getCities(country.selectedItem.data);
token.addResponder(new mx.rpc.Responder(onCitiesResult, onCitiesFault));
}
private function onCitiesResult(e:ResultEvent):void {
dataGrid.dataProvider=e.result;
}
private function onCitiesFault(e:FaultEvent):void {
Alert.show(e.fault.faultString, "Fault");
}
private function changeComboBoxEvt(e:Event):void {
var token:AsyncToken = ws.getCities(e.currentTarget.selectedItem.data);
token.addResponder(new mx.rpc.Responder(onCitiesResult, onCitiesFault));
}
]]>
</fx:Script>
<s:Panel title="RDC with FB4 & BlazeDS">
<s:VGroup>
<mx:ComboBox id="country" width="150" change="changeComboBoxEvt(event)">
<mx:ArrayList>
<fx:Object label="Netherlands" data="NL"/>
<fx:Object label="Germany" data="DE"/>
</mx:ArrayList>
</mx:ComboBox>
<mx:DataGrid x="53" y="36" id="dataGrid" >
<mx:columns>
<mx:DataGridColumn headerText="country" dataField="country"/>
<mx:DataGridColumn headerText="name" dataField="name"/>
</mx:columns>
</mx:DataGrid>
</s:VGroup>
</s:Panel>
</s:Application>
