Preserving MapML CRS in layer group links too

src/extension/mapml/src/test/java/org/geoserver/web/demo/PreviewLayerTest.java

@@ -0,0 +1,40 @@
+/* (c) 2024 Open Source Geospatial Foundation - all rights reserved
+ * This code is licensed under the GPL 2.0 license, available at the root
+ * application directory.
+ */
+package org.geoserver.web.demo;
+
+import static org.junit.Assert.assertEquals;
+
+import org.geoserver.catalog.Catalog;
+import org.geoserver.catalog.LayerGroupInfo;
+import org.geoserver.data.test.MockData;
+import org.geoserver.web.GeoServerWicketTestSupport;
+import org.geotools.geometry.jts.ReferencedEnvelope;
+import org.geotools.referencing.CRS;
+import org.junit.Test;
+
+public class PreviewLayerTest extends GeoServerWicketTestSupport {
+
+    /**
+     * Check MapML srs is preserved for layer groups
+     *
+     * @throws Exception
+     */
+    @Test
+    public void testMapmlFormatLink() throws Exception {
+        Catalog cat = getCatalog();
+
+        LayerGroupInfo lg = cat.getFactory().createLayerGroup();
+        lg.setName("foo");
+        lg.setWorkspace(cat.getWorkspaceByName("sf"));
+        lg.getLayers().add(cat.getLayerByName(getLayerId(MockData.PRIMITIVEGEOFEATURE)));
+        lg.setBounds(new ReferencedEnvelope(0, 1, 0, 1, CRS.decode("MapML:OSMTILE")));
+        PreviewLayer layer = new PreviewLayer(lg);
+        layer.getWmsLink(
+                (r, p) -> {
+                    assertEquals("MapML:OSMTILE", p.get("srs"));
+                    assertEquals("0.0,0.0,1.0,1.0", p.get("bbox"));
+                });
+    }
+}

src/web/demo/src/main/java/org/geoserver/web/demo/PreviewLayer.java

@@ -22,6 +22,7 @@
 import org.geoserver.catalog.LayerGroupInfo;
 import org.geoserver.catalog.LayerInfo;
 import org.geoserver.catalog.PublishedType;
+import org.geoserver.catalog.ResourcePool;
 import org.geoserver.ows.URLMangler.URLType;
 import org.geoserver.ows.util.ResponseUtils;
 import org.geoserver.security.DisabledServiceResourceFilter;
@@ -34,6 +35,8 @@
 import org.geotools.api.feature.type.AttributeType;
 import org.geotools.api.feature.type.FeatureType;
 import org.geotools.api.feature.type.Name;
+import org.geotools.api.referencing.FactoryException;
+import org.geotools.api.referencing.crs.CoordinateReferenceSystem;
 import org.geotools.api.util.ProgressListener;
 import org.geotools.data.util.DefaultProgressListener;
 import org.geotools.geometry.jts.ReferencedEnvelope;
@@ -149,10 +152,8 @@ public GetMapRequest getRequest() {
             if (groupInfo != null) {
                 ReferencedEnvelope bounds = groupInfo.getBounds();
                 request.setBbox(bounds);
-                String srs =
-                        GML2EncodingUtils.toURI(
-                                bounds.getCoordinateReferenceSystem(), SrsSyntax.AUTH_CODE, false);
-                request.setSRS(srs);
+                request.setCrs(bounds.getCoordinateReferenceSystem());
+                request.setSRS(lookupSRSFromBounds(bounds));
             }
             try {
                 DefaultWebMapService.autoSetBoundsAndSize(request);
@@ -167,6 +168,18 @@ public GetMapRequest getRequest() {
         return request;
     }
 
+    private static String lookupSRSFromBounds(ReferencedEnvelope bounds) {
+        // try first a method that retains the native authority code, otherwise fall back on
+        // GML2EncodingUtils, which prefers the EPSG authority
+        CoordinateReferenceSystem crs = bounds.getCoordinateReferenceSystem();
+        if (crs == null) return null;
+        try {
+            return ResourcePool.lookupIdentifier(crs, false);
+        } catch (FactoryException e) {
+            return GML2EncodingUtils.toURI(crs, SrsSyntax.AUTH_CODE, false);
+        }
+    }
+
     /** Expands the specified name into a list of layer info names */
     private List<MapLayerInfo> expandLayers(Catalog catalog) {
         List<MapLayerInfo> layers = new ArrayList<>();
@@ -355,6 +368,7 @@ private String findFeatureTypeGmlVersion(AttributeType featureType) {
         AttributeType parent = featureType.getSuper();
         return findFeatureTypeGmlVersion(parent);
     }
+
     /**
      * Returns true if serviceName is available for resource, otherwise false
      *