How to read external GeoJSON file from openlayers? - dictionary

Question

I have to draw some lines by OpenLayers. The line features are coded as GeoJSON format. My code is ok for hard coded GeoJSON features. But, if I put this features in separate file and try to load it. It just does not work. I do not know what is the wrong with my loading external GeoJSON file. I have given both the code.
Code 1:
// This code is ok with hard coded GeoJSON features
map.addControl(new OpenLayers.Control.LayerSwitcher());
vectorLayer = new OpenLayers.Layer.Vector("Lines");
var myGeoJSON = { "type": "FeatureCollection",
"features":
[
{ "type": "Feature", "properties": { "LENGTH": 756.304000}, "geometry": { "type": "LineString", "coordinates": [ [ 18.105018, 59.231027 ], [ 18.104176, 59.230737 ], [ 18.103928, 59.230415 ], [ 18.103650, 59.230336 ], [ 18.103028, 59.230463 ], [ 18.102491, 59.230418 ], [ 18.101976, 59.230237 ], [ 18.100893, 59.230110 ], [ 18.100117, 59.230016 ], [ 18.097715, 59.230262 ], [ 18.096907, 59.230376 ], [ 18.096637, 59.230405 ], [ 18.096578, 59.230428 ], [ 18.096429, 59.230450 ], [ 18.096336, 59.230479 ], [ 18.096108, 59.230534 ], [ 18.095971, 59.230600 ], [ 18.095925, 59.230633 ], [ 18.095891, 59.230665 ], [ 18.094000, 59.231676 ], [ 18.093864, 59.231720 ] ] } }
,
{ "type": "Feature", "properties": { "LENGTH": 1462.390000}, "geometry": { "type": "LineString", "coordinates": [ [ 17.877073, 59.461653 ], [ 17.877116, 59.461598 ], [ 17.876936, 59.461507 ], [ 17.876936, 59.461323 ], [ 17.876773, 59.461098 ], [ 17.876430, 59.460885 ], [ 17.876413, 59.460553 ], [ 17.876576, 59.460280 ], [ 17.876575, 59.460078 ], [ 17.876762, 59.460060 ], [ 17.877371, 59.460042 ], [ 17.877808, 59.460046 ], [ 17.878641, 59.460046 ], [ 17.879010, 59.460078 ], [ 17.879337, 59.460044 ], [ 17.879526, 59.459878 ], [ 17.879749, 59.459563 ], [ 17.880058, 59.459538 ], [ 17.880435, 59.459503 ], [ 17.887550, 59.453608 ], [ 17.887696, 59.453430 ], [ 17.887971, 59.453150 ], [ 17.888221, 59.452843 ], [ 17.888246, 59.452721 ], [ 17.888435, 59.452609 ], [ 17.888470, 59.452568 ], [ 17.888517, 59.452410 ] ] } }
]
};
var geojson_format = new OpenLayers.Format.GeoJSON({
'internalProjection': map.baseLayer.projection,
'externalProjection': new OpenLayers.Projection("EPSG:4326")
});
map.addLayer(vectorLayer);
vectorLayer.addFeatures(geojson_format.read(myGeoJSON));
map.setCenter(
new OpenLayers.LonLat(18.068611, 59.329444).transform(
new OpenLayers.Projection("EPSG:4326"),
map.getProjectionObject()
), 10
);
Code 2: This code shows an error that it could not load features
//This code does not work because it can not load the external GeoJSON file
map.addControl(new OpenLayers.Control.LayerSwitcher());
vectorLayer = new OpenLayers.Layer.Vector("Lines");
var myGeoJSON = new OpenLayers.Layer.Vector("Lines", {
strategies: [new OpenLayers.Strategy.Fixed()],
protocol: new OpenLayers.Protocol.HTTP({
url: "ml/lines.json"
})
});
var geojson_format = new OpenLayers.Format.GeoJSON({
'internalProjection': map.baseLayer.projection,
'externalProjection': new OpenLayers.Projection("EPSG:4326")
});
map.addLayer(vectorLayer);
vectorLayer.addFeatures(geojson_format.read(myGeoJSON));
map.setCenter(
new OpenLayers.LonLat(18.068611, 59.329444).transform(
new OpenLayers.Projection("EPSG:4326"),
map.getProjectionObject()
), 10
);
Thanks in advance

Answer 1

geojson_layer = new OpenLayers.Layer.Vector("GeoJSON", {
strategies: [new OpenLayers.Strategy.Fixed()],
protocol: new OpenLayers.Protocol.HTTP({
url: "ml/lines.json",
format: new OpenLayers.Format.GeoJSON()
})
});
See my little example.