Examples

The following are example configurations of layers in GeoWebCache.

Minimal configuration

This example shows the absolute minimum information needed to configure a layer in GeoWebCache together with the assumptions made.

At the very least, GeoWebCache needs to know only two things to cache a layer:

  1. The URL of the WMS server
  2. The name of the layer as defined in the WMS
<gwcConfiguration>
  <!-- ... -->
  <layers>
    <!-- ... -->
    <wmsLayer>
      <name>topp:states</name>
      <wmsUrl><string>http://demo.opengeo.org/geoserver/wms</string></wmsUrl>
    </wmsLayer>
    <!-- ... -->
  </layers>
</gwcConfiguration>

In this case, the assumptions are:

  1. WMS version 1.1.1 is used (version=1.1.1)
  2. The layer will be valid for EPSG:4326 and EPSG:900913, with world extent (srs=EPSG:4326, srs=EPSG:900913)
  3. The layer name on the WMS is identical to the name of the layer as specified here (layers=topp:states)
  4. The supported image format is PNG (image/png) and JPEG (image/jpeg) (format=image/png, format=image/jpeg)
  5. The default style used (styles=)
  6. Exceptions are reported inside images (exceptions=application/vnd.ogc.se_inimage)
  7. Requests using OpenLayers are made with transparent=true

Explicit blob store configuration

Unless otherwise specified, the tiles produced by a wmsLayer will be persisted to the cache defined by the default blob store. The blobStoreId element allows to define an alternate blob store where to store the layer tiles. See the Storage page for more information on how to configure blob stores.

In this example, the layer is configured to use the myBlobStore blob store, which must be defined in the blobStores section of gwcConfiguration with the same identifier.

<gwcConfiguration>
  <!-- ... -->
  <layers>
    <!-- ... -->
    <wmsLayer>
      <blobStoreId>myBlobStore</blobStoreId>
      <name>topp:states</name>
      <wmsUrl><string>http://demo.opengeo.org/geoserver/wms</string></wmsUrl>
    </wmsLayer>
    <!-- ... -->
  </layers>
</gwcConfiguration>

Simple configuration

The following is a more realistic but still simple example for configuring a layer in GeoWebCache.

In this case, the requirements are:

  1. Combine two layers from a WMS, (nurc:Img_Sample and topp:states)
  2. Name the layer img states (note the space in the name)
  3. Set the projection to EPSG:4326
  4. Limit the extent to the continental United States
  5. Support only GIF
  6. Draw the background color (where there is no data) in a shade of blue
  7. Set the transparency to false

The resulting configuration would look like:

<gwcConfiguration>
  <!-- ... -->
  <layers>
    <!-- ... -->
      <wmsLayer>
        <name>img states</name>
        <metaInformation>
          <title>Nicer title for Image States</title>
          <description>This is a description. Fascinating.</description>
        </metaInformation>
        <mimeFormats><string>image/gif</string></mimeFormats>
        <gridSubsets>
          <gridSubset>
            <gridSetName>EPSG:4326</gridSetName>
            <extent>
              <coords>
                <double>-129.6</double>
                <double>3.45</double>
                <double>-62.1</double>
                <double>70.9</double>
              </coords>
            </extent>
          </gridSubset>
        </gridSubsets>
        <wmsUrl>
          <string>http://demo.opengeo.org/geoserver/wms</string>
        </wmsUrl>
        <wmsLayers>nurc:Img_Sample,topp:states</wmsLayers>
        <transparent>false</transparent>
        <bgColor>0x0066FF</bgColor>
      </wmsLayer>
    <!-- ... -->
  </layers>
</gwcConfiguration>

Note

The reference to the gridset EPSG:4326 may look a bit mysterious. It is one of only two gridsets (the other being EPSG:900913) that is automatically defined inside GeoWebCache. Other gridsets will need to be configured manually. (Learn more about Gridsets and Gridsubsets and Custom projections.)

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