Get layer name in SLD

Question

Is there any element or function we can use to get the current layer name in SLD? We're requesting multiple layers, and would like to use the same style for each one, but with small customizations such as color change etc. depending on the layer.

I haven't been able to find any documentation that allows for a use case like this, without creating a new SLD for each layer type.

I am kind of confuse with the OL tag of the question, you want to make changes to a style using OL? then why you need the layer name in SLD? — cabesuon, Apr 01 '20 at 06:25
We're using Openlayers TileWMS on the client. If anyone could find another solution using Openlayers, then that would be fine :) The Openlayes community has a lot of spatial knowledge. — Stsje, Apr 01 '20 at 07:33
Agree .. Let me see if I understand, you are publishing multiple layers with one base style, and you want to know how to change some style properties in OL, like color, based on the layer? — cabesuon, Apr 01 '20 at 12:20
Exactly! We could of course, instead of using one style, have a new style for each layer. It just seems kind of redundant to have exactly the same style copied 24 times (24 layers), but with a minor color or font size change in each one. — Stsje, Apr 01 '20 at 12:43

cabesuon · Answer 1 · 2020-04-02T17:37:06.540

[WFS]

Here I made an example for you, to show you how you can do the simple modifications that you mention.

In the example below, instead of modifying the layer style I modify the features style, it the same thing I just found simple to exemplify. So, in order to work in your case you just need to obtain the layer style and made the changes in the same way as the example.

<!doctype html>
<html lang="en">
  <head>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/css/ol.css" type="text/css">
    <style>
      .map {
        height: 400px;
        width: 100%;
      }
    </style>
    <script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.1.1/build/ol.js"></script>
    <title>Simple Style Change</title>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script type="text/javascript">
    // base style default of features
  // features
    const radius = 20000;
    const cx = -80;
    const cy = 35;
    const fonts = [
      '1.2em "Fira Sans", sans-serif',
      'italic 1.2em "Fira Sans", serif',
      'italic small-caps bold 16px/2 cursive',
      'small-caps bold 24px/1 sans-serif',
      'caption'
    ];
    const baseStyle = new ol.style.Style({
      stroke: new ol.style.Stroke({
        color: 'rgba(0, 0, 0, 1)',
        width: 1
      }),
      fill: new ol.style.Fill({
        color: 'rgba(0, 0, 0, 0.1)'
      }),
      text: new ol.style.Text({
        stroke: new ol.style.Stroke({color: '#ffffff', width: 3})
      })
    });
    // map
    const view = new ol.View({
      center: ol.proj.fromLonLat([cx-6, cy]),
      zoom: 7
    });
    const vlayer = new ol.layer.Vector({
      source: new ol.source.Vector(),
      style: baseStyle
    });
    const map = new ol.Map({
   target: 'map',
   layers: [
    new ol.layer.Tile({
     source: new ol.source.OSM()
    }),
        vlayer
   ],
   view
  });
    // add features
    const features = [];
    let feat, style, fill, text;
    for (let i = 0; i < 20; i++) {
      feat = new ol.Feature({
        geometry: ol.geom.Polygon.circular([cx-i, cy], radius)
        .transform('EPSG:4326', 'EPSG:3857')
      });
      style = vlayer.getStyle().clone();
      fill = vlayer.getStyle().getFill().clone();
      fill.setColor(`rgba(${i*12},${i*12},${i*12},0.5)`)
      style.setFill(fill);
      text = vlayer.getStyle().getText().clone();
      text.setFont(fonts[i % fonts.length]);
      text.setText(`${i}`);
      style.setText(text);
      feat.setStyle(style);
      features.push(feat);
    }
    vlayer.getSource().addFeatures(features);
    </script>
  </body>
</html>

UPDATE for WMS

For WMS you can use two parameter to dynamically change the style on request.

styles: comma-separated value of the style names to applied, default style is apply on empty value. In this case, you have to define a set of styles with the simple changes you want and then you use the names of these style with the layers in OL.
sld_body: the SLD XML text you want to apply to the map. In this case you have a base SLD and you modify it with JavaScript and use it with the layers in OL.

On OL you can specify this parameters, assuming that you are using TileWMS, on creation with option parameter params or with the method updateParams.

GeoServer - WMS

OL API - TileWMS

Sorry I do not see how we can use your example with wms layers. Yes it would be easy to do with vector features — Stsje, Apr 02 '20 at 11:35
Sorry I miss understood the question .. Anyway I have updated the answer, check if it helps on your case — cabesuon, Apr 02 '20 at 17:37

Get layer name in SLD

1 Answers1