网络分析与网络数据集—功能调用REST API

ArcGIS 9.3实现了REST的架构，开始支持RIA（富英特网应用），包括ArcGIS API for Flex、ArcGIS API for Silverlight、ArcGIS JavaScript API。RIA是一种前端的开发方式，而与后台ArcGIS Server的交互是通过REST API实现的。

REST的架构，简单的说就是把所有的资源和功能都抽象为一个URL地址，通过一个URL地址就能访问ArcGIS Server提供的资源服务或者功能服务。ArcGIS Server 10 REST API实现了路径分析、最近设施查询、服务区域分析（10之前只支持路径分析）。ArcGIS API for Flex、ArcGIS API for Silverlight、ArcGIS JavaScript API都实现了相应的task来调用网络分析的功能，方法都差不多，我们看一下Flex的例子。

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:esri="http://www.esri.com/2008/ags"
xmlns:s="library://ns.adobe.com/flex/spark"
pageTitle="Routing with the ArcGIS API for Flex">

<s:layout>
<s:VerticalLayout paddingTop="10"/>
</s:layout>

<fx:Script>
<!--[CDATA[
import com.esri.ags.FeatureSet;
import com.esri.ags.Graphic;
import com.esri.ags.events.MapMouseEvent;
import com.esri.ags.events.RouteEvent;
import com.esri.ags.tasks.supportClasses.RouteResult;
import mx.controls.Alert;
import mx.rpc.events.FaultEvent;

private var lastRoute:Graphic;

// Add stops to caculate route
private function mapClickHandler(event:MapMouseEvent):void
{
var stop:Graphic = new Graphic(event.mapPoint, stopSymbol);
graphicsLayer.add(stop);

stops.push(stop);
if (stops.length > 1)
{
routeTask.solve(routeParams);
}
}

// Event handler after route solver excutes successfully
private function solveCompleteHandler(event:RouteEvent):void
{
var routeResult:RouteResult = event.routeSolveResult.routeResults[0];
routeResult.route.symbol = routeSymbol;
graphicsLayer.remove(lastRoute);
lastResult = routeResult.route;
graphicsLayer.add(lastRoute);

}

// Event handler after route solver excuetes unsuccessfully
private function faultHandler(event:FaultEvent):void
{
Alert.show(event.fault.faultString + "/n/n" + event.fault.faultDetail, "Routing Error " + event.fault.faultCode);
// remove last stop (or both stops if only two)
if (stops.features.length <= 2)
{
graphicsLayer.clear();
}
else
{
graphicsLayer.remove(stops.features.pop());
}
}
]]-->
</fx:Script>

<!-- start declarations -->
<fx:Declarations>
<esri:RouteTask id="routeTask"
concurrency="last"
fault="faultHandler(event)"
requestTimeout="30"
showBusyCursor="true"
solveComplete="solveCompleteHandler(event)"
url="http://tasks.arcgisonline.com/ArcGIS/rest/services/NetworkAnalysis/ESRI_Route_NA/NAServer/Route"/>

<esri:RouteParameters id="routeParams">
<esri:stops>
<esri:FeatureSet>
<esri:features>
<fx:Array id="stops"/>
</esri:features>
</esri:FeatureSet>
</esri:stops>
</esri:RouteParameters>

<esri:SimpleMarkerSymbol id="stopSymbol"
size="15"
style="triangle" mce_style="triangle">
<esri:SimpleLineSymbol width="4"/>
</esri:SimpleMarkerSymbol>

<esri:SimpleLineSymbol id="routeSymbol"
alpha="0.5"
color="0x0000FF"
width="5"/>
</fx:Declarations>
<!-- end declarations -->

<s:Label fontSize="12" text="Click on the map to add stops for your routing"/>
<esri:Map mapClick="mapClickHandler(event)">
<esri:ArcGISTiledMapServiceLayer url="http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer"/>
<esri:GraphicsLayer id="graphicsLayer"/>
</esri:Map>
</s:Application>

程序看得够多了，尽管是另一种开发方式，但是并不是那么陌生和不可理解。有两个地方特别指出，网络分析参数的设置比如U-Turn的类型、考虑哪些限制、是否考虑高速优先，包括stops、barriers都通过RouteParameters设置；计算的结果包括路径、方向提示通过RouteResult获取。