[OpenLayers-Users] How to validate whether the BBOX strategy works successfully?

[Yasemin YILMAZ]

Hi all,

I want to send requests to our feature server that asks only data within
the viewable map extent. So I've used BBOX strategy and HTTP Protocol as
following code.

            mVectorLayer = new OpenLayers.Layer.Vector("Overlay", {
                strategies: [new OpenLayers.Strategy.BBOX()],
                protocol: new OpenLayers.Protocol.HTTP({
                    url: 'http://localhost:56786/jlist.geojson',
                    format: new OpenLayers.Format.GeoJSON({
                        'read': myReadFunction,
                        'internalProjection': map.baseLayer.projection,
                        'externalProjection': new
OpenLayers.Projection("EPSG:4326")
                    })
                }),
                projection: new OpenLayers.Projection("EPSG:900913")
            });

I want to validate that our feature server receives the requests for only
data within the viewable map. So I've added a feature outside the viewable
map to the geojson file shown at below.

{ "type": "FeatureCollection",
  "features": [
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [29.0, 41.060]},
        "properties": {"name": "IST J1", "img": "img/marker.png"}
      },
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [29.0, 41.100]},
        "properties": {"name": "IST J2", "img": "img/marker.png"}
      },
      { "type": "Feature",
        "geometry": {"type": "Point", "coordinates": [59.0, 41.100]},
        "properties": {"name": "IST J3", "img": "img/marker.png"}
      }
  ]
}

To validate, I've added an alert to the function myReadFunction which shows
the json string. But the alert shows all features in geojson file. I
suppose our feature server sends all geojson content instead of viewable
features? Do I comment it as right?  How can I validate or observe whether
the BBOX strategy works successfully?

        function myReadFunction(json, type, filter) {
            alert("json: " + json);

            type = (type) ? type : "FeatureCollection";
            var results = null;
            var obj = null;
            if (typeof json == "string") {
                obj = OpenLayers.Format.JSON.prototype.read.apply(this,
                                                              [json,
filter]);
            } else {
                obj = json;
            }
            if (!obj) {
                OpenLayers.Console.error("Bad JSON: " + json);
            } else if (typeof (obj.type) != "string") {
                OpenLayers.Console.error("Bad GeoJSON - no type: " + json);
            } else if (this.isValidType(obj, type)) {
                switch (type) {
                    case "Geometry":
                        try {
                            results = this.parseGeometry(obj);
                        } catch (err) {
                            OpenLayers.Console.error(err);
                        }
                        break;
                    case "Feature":
                        try {
                            results = this.parseFeature(obj);
                            results.type = "Feature";
                        } catch (err) {
                            OpenLayers.Console.error(err);
                        }
                        break;
                    case "FeatureCollection":
                        // for type FeatureCollection, we allow input to be
any type
                        results = [];
                        switch (obj.type) {
                            case "Feature":
                                try {
                                    results.push(this.parseFeature(obj));
                                } catch (err) {
                                    results = null;
                                    OpenLayers.Console.error(err);
                                }
                                break;
                            case "FeatureCollection":
                                for (var i = 0, len = obj.features.length;
i < len; ++i) {
                                    try {

results.push(this.parseFeature(obj.features[i]));
                                    } catch (err) {
                                        results = null;
                                        OpenLayers.Console.error(err);
                                    }
                                }
                                break;
                            default:
                                try {
                                    var geom = this.parseGeometry(obj);
                                    results.push(new
OpenLayers.Feature.Vector(geom));
                                } catch (err) {
                                    results = null;
                                    OpenLayers.Console.error(err);
                                }
                        }
                        break;
                }
            }
            return results;
}

Thanks a lot for your helps and explanations,
Yasemin
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