EDN: ESRI Developer Network
The MapServer component provides programmatic access to the contents of a map document on disk, and creates images of the map contents based on user requests. Designed for use in building map-based web services and web applications.
Use the ISupportErrorInfo method InterfaceSupportsErrorInfo to determine if the object supports extended error information. If the object supports extended error info, VC++ developers should use the OLE/COM IErrorInfo interface to access the ErrorInfo object. Visual Basic developers should use the global error object Err to retrieve this extended error information.
| Interfaces | Description |
|---|---|
| ILogSupport (esriSystem) | Provides access to methods for initializing an object for logging. |
| IMapServer | Provides access to members that serve maps. |
| IMapServerData | Provides access to map features and their values. |
| IMapServerInit | Provides access to members that support initializing a map server. |
| IMapServerInit2 | Provides access to additional members that support initializing a map server. |
| IMapServerLayout | Provides access to members that serve layout components of maps. |
| IMapServerObjects | Provides access to core objects contained within the map document. |
| IMapServerObjects2 | Provides access to core objects contained within the map document. |
| IObjectActivate (esriSystem) | Provides access to methods for activating and deactivating objects. |
| IObjectConstruct (esriSystem) | Provides access to methods for constructing an object. |
| IRequestHandler (esriSystem) | Provides access to members that control handing of request messages. |
| IRequestHandler2 (esriSystem) | Provides access to members that control handing of request messages. |
| IServerObject (esriServer) | Provides access to properties of a map or geocode server object. |
| IServerObjectExtensionManager (esriServer) | Provides access to members that help locate installed server object extensions. |
| ISupportErrorInfo | Indicates whether a specific interface can return Automation error objects. |
| ITiledMapServer | Provides access to members that serve tiled maps. |
MapServer is a coarse-grained ArcObject. This object allows users to display and query ArcGIS map documents in either desktop, LAN/WAN, or internet development environments. In the desktop environment you can use MapServer, as well as other coarse-grained objects as a "short-cut" for ArcObjects development. Operations that took many lines of code may now just take a few. In a server environment, MapServer objects can be accessed via Distributed COM (DCOM) over a TCP/IP connection (Intranet) or via SOAP/XML over an HTTP connection (Internet).
The MapServer coclass contains several interfaces with basic functions for displaying (IMapServer and IMapServerLayout) and querying (IMapServer and IMapServerData) an ArcGIS map document (.mxd or .pmf).
In addition to MapServer, a number of MapServer objects are defined to represent input and output parameters for methods on MapServer interfaces. For example, the IMapServer method ExportMapImage requires two inputs: a description of the map to be exported and a description of the output parameters. These inputs are captured in the MapDescription and ImageDescription objects.
Though the methods and properties available through MapServer and its associated objects offer important mapping functionality, they cannot possibly encapsulate all that ArcObjects offers. In many cases you may want to use other, finer-grained, ArcObjects in conjunction with MapServer. You can do this using the IMapServerObjects interface. Through this interface you can access ILayer, IMap and IPageLayout. For example, you can make changes to the map, such as adding a new layer, using IMap.
It is very important to distinguish between temporary and permanent changes to the MapServer object. A temporary change would include changes to the MapDescription or LayerDescription using IMapDescription and ILayerDescription. For example, you might change the geographic extent of a map (MapArea) or change the visibility of a layer (Visible). These changes can be temporary and valid for the duration of the call. Once the call has ended the MapServer object returns to it's default state.
Permanent changes to the MapServer object can be done in two ways. The first is by changing MapServer properties using such interfaces as IMapDescription and ILayerDescription and then calling the IMapServerObjects method ApplyMapDescription. This will update the state of the fine-grained ArcObjects. Another way to change the MapServer object is to access the underlaying fine-grained ArcObjects directly using the methods on IMapServerObjects, make a change such as adding a new layer or changing a layer's rendering, and then calling RefreshServerObjects. This refreshes the MapServer object with the current state held by the fine-grained ArcObjects.
You should use non-pooled objects when permently changing the state of fine-grained ArcObjects.
Only certain symbols are supported when working with the MapServer WSDL or accessing a MapServer object through an AGSServerConnection (LAN or internet). These include ISimpleMarkerSymbol, ICharacterMarker, IPictureMarker, ISimpleLineSymbol, ISimpleFillSymbol and IPictureFill.
A MapServer service can have an associated tiled map cache. This cache is a collection of pre-rendered map tiles that are used for the display of the map service. A cache can either be a fused cache where all layers within the map service are cached or a Multi-layer cache where only select map layers are cached. Working with MapServer and a cached map service can be different than working with a map service without a cache. Though you will be able to query against a cached map service just as you would a non-cached map service, you will see differences when working with cached map service's MapDescription and the LayerDescription of any map layer belonging to a cache.
If the map service has a fused cache custom graphics, including the rendering of selected features, cannot be applied to the MapDescription. In addition, any changes made to the LayerDescription of any of the map layers, such as applying a definition expression, applying a selection buffer, toggling the visibility of labels or changing the visibility of the layer itself are ignored. When the map service has a Multi-layer cache changes to the MapDescription are honored. You will be able to render custom graphics and selection features, including features belonging to cached layers. However, you will not be able to apply a definition expression to or toggle the value of the ScaleSymbol property of individual layers that are cached. These will be ignored. Finally, applying a new spatial reference on cached map services though IMapDescription will not work. The cached layers will not draw. You will need to use ITileCacheInfo to change the spatial reference.
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