Query a GeoServer instance
This example demonstrates how to build an OGC Filter to query a GeoServer WFS instance and use the results in a choice list. For this particular example, we want to list all the streets within 100 meters of our current location so we can do some field addressing without having to enter the street names. MassGIS maintains a GeoServer instance which includes roads from the Massachusetts Department of Transportation (MassDOT). We will be querying the massgis:GISDATA.EOTROADS_ARC layer, parsing the results as GeoJSON, and adding the STREETNAME property to a choice list. NOTE: The LATITUDE and LONGITUDE functions will only return values if a record's geometry type is set to Point, and there is a location set. Unless you have enabled Lines and Polygons for your app, the Point type will be the only available geometry type for records in the app.
ON('change-geometry', function(event) {
// build spatial "distance within" filter (http://docs.geoserver.org/latest/en/user/filter/filter_reference.html#filter-fe-reference)
var filter = "<Filter xmlns:gml='http://www.opengis.net/gml'>" +
"<DWithin>" +
"<PropertyName>SHAPE</PropertyName>" +
"<gml:Point srsName='http://www.opengis.net/gml/srs/epsg.xml#4326'>" +
"<gml:coordinates>" + LONGITUDE() + "," + LATITUDE() + "</gml:coordinates>" +
"</gml:Point>" +
"<Distance units='m'>100</Distance>" +
"</DWithin>" +
"</Filter>";
// configure request options
var options = {
url: 'https://giswebservices.massgis.state.ma.us/geoserver/wfs',
qs: {
request: 'getfeature',
version: '1.0.0',
service: 'wfs',
typename: 'massgis:GISDATA.EOTROADS_ARC',
propertyname: 'STREETNAME',
outputformat: 'json',
filter: filter
}
};
// give the user a loading indicator while it's fetching the data from GeoServer
PROGRESS('Searching for nearby streets ...');
// configure the http request
REQUEST(options, function(error, response, body) {
PROGRESS(); // dismiss the loading indicator
if (error) {
ALERT('Error with request: ' + INSPECT(error));
} else {
var data = JSON.parse(body); // parse the JSON response
var features = data.features; // grab the GeoJSON features
var streets = []; // array holder for nearby streets
// loop through the features returned
for (var i = 0; i < features.length; i++) {
var streetName = features[i].properties.STREETNAME;
// if array doesn't already contain streetname, add it
if (streets.indexOf(streetName) === -1) {
streets.push(streetName);
}
}
// if we've got some streets, use them in the choice list (sorted alphabetically)
if (streets.length > 0) {
SETCHOICES('street_name', streets.sort());
} else {
ALERT('No nearby streets found... Are you sure you are in Massachusetts?');
}
}
});
});
NOTE: The LATITUDE and LONGITUDE functions will only return values if a record's geometry type is set to Point, and there is a location set. Unless you have enabled Lines and Polygons for your app, the Point type will be the only available geometry type for records in the app.
Updated 6 months ago