External Map Source Adapter - MapViewer

Question

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Hi
I am developing an application using Oracle Maps of OracleMapViewer 10.1.3 using OC4J
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The objective of this exercise is to make use of a cache generated by a non-MapViewer solution. The cache is stored at an external location and can be accessed by sending multiple HTTP requests. For any given extent, multiple HTTP requests needs to be sent to access the individual tiles covering the given area.
http://servername/mapname/cache?level=0&row=11&column=1
http://servername/mapname/cache?level=0&row=11&column=2
http://servername/mapname/cache?level=0&row=12column=1
http://servername/mapname/cache?level=0&row=12&column=2
The logic to identify the tiles is also available. The problem is that the getMapTileRequest(...) returns only one string and this when passed would return only one image tile. (Correct me if my understanding is wrong)
public abstract class MapSourceAdapter
<strong>public abstract String getMapTileRequest(TileDefinition tile);</strong>
public byte[] getTileImageBytes(TileDefinition tile) ;
public Properties getProperties() ;
One option is to have a servlet at the other end that would accept the extent and zoom level and then identify the tiles. But still it is not clear as whether MapViewer will accept one response or multiple responses from the external server.
Need some guidance in this aspect
Regards
Govindarajan
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Answer 1

1. The mapviewer tile servlet can response to multiple tile requests simultaneously. It makes multiple calls to the getMapTileRequest method, each of which gets the URL for one tile. So if you can define the map tile layer(map cache instance) in such a way that its tiles have the same size as the external tiles, mapviewer should be able to handle the tile requests without problem. You also need to modify the XML tile layer(map cache instance) definition and add parameter "fetch_larger_tiles" to the root node and set its value to "false". Without this change, mapviewer will fetch map images that are several times larger than the actual tiles and cut them into tiles later on.
2. With the latest patch, you can define a custom tile layer on the client side and fetch the tiles directly from the non-mapviewer tile server. Because this approach does not duplicate the tiles in mapviewer's tile cache, it is better than 1 if the non-mapviewer tile server can serve the tiles as fast as mapviewer. Demo #50 on the mapviewer tutorial page shows how to use custom tile layer.