How to get native bounding box (minx,miny,maxx,maxy) using OpenLayers?

Question

I am trying to develop a GIS application using GeoServer and OpenLayers. I want to get the bounds from GeoServer Native Bounding Box data of a layer instead of manually hard code:

var map;
var key = 0;
var fromNo = "";
var toNo = "";
var colorId = "";
var count = 0;
function init(){
format = 'image/png';   
if(map)
map.destroy();
var bounds = new OpenLayers.Bounds(
    8568700.4305088, 1677704.30921461,
                    9195694.68892519, 2070938.3484273
);
var options = {
    controls: [],
    maxExtent: bounds,
    maxResolution: "auto",
    projection: "EPSG:900913",
    units: 'degrees',
    minZoomLevel: 0, numZoomLevels:15,maxZoomLevel:15   
};
var  click_ap ;
var values = new Array();
map = new OpenLayers.Map('map', options);
    $('.selectionTable tr').each(function() {
        fromNo  =  $(this).closest("tr").find(".fromNo").val();
        toNo    = $(this).closest("tr").find(".toNo").val();
        colorId = $(this).closest("tr").find(".colorSelect option:selected").val();
        apZoomLevel1 = new OpenLayers.Layer.WMS(
                   "ap",
                "http://localhost:8090/geoserver/scmapWithSelectColor/wms??request=getCapabilities ",
                    {'layers': 'scMapQuery', 
                    viewparams: 'fromNo:'+fromNo+';toNo:'+toNo+';colorId:'+colorId+';',
                    'transparent': true,isbaselayer:false},{
                       singleTile: true,opacity: .5
                    }
              );
              values.push(apZoomLevel1);
});
click_ap = new OpenLayers.Control.WMSGetFeatureInfo({
 url:'http://localhost:8090/geoserver/scmapWithSelectColor/wms', 
 title: 'Identify features by clicking',
 layers: [apZoomLevel1],
 queryVisible: true,
 eventListeners: {
 getfeatureinfo: function(event) {

if (ContentFilterAp(event.text,'hos').length>0){
//alert("localitieslevel3");
    map.addPopup(new OpenLayers.Popup.FramedCloud(
        "apZoomLevel1", 
        map.getLonLatFromPixel(event.xy),
        null,
        ContentFilterAp(event.text,'hos'),
        null,
        true
            ));}
        }
        }
    });
gmap = new OpenLayers.Layer.Google
(
    "Google Streets"  
);
ghyb = new OpenLayers.Layer.Google
(
   "Google Hybrid",
   {type: google.maps.MapTypeId.HYBRID}
);
    map.addControl(new OpenLayers.Control.Navigation());

    map.addControl(new OpenLayers.Control.LayerSwitcher({'div':OpenLayers.Util.getElement('layerswitcher')}));
    map.addLayers([gmap,ghyb]);
    var length = values.length;
    if(length > 0)
    {
        for(i=0;i<length;i++)
        {
            //debugger;
            map.addLayers([values[i]]);
        }
    }
    map.addControl(new OpenLayers.Control.PanZoomBar({
    }));
    map.addControl(new OpenLayers.Control.Navigation());
    map.addControl(new OpenLayers.Control.Scale($('scale')));
    map.addControl(new OpenLayers.Control.MousePosition({element: $('location')}));
    map.zoomToExtent(bounds);
    map.addControl(click_ap);
    click_ap.activate();
    map.events.register('zoomend', this, function (event) {
}); }

Actually above bounds are hard coded but actually apzoomlevel1 have native bounds how to get those one? actually those bounds useful in map.zoomToExtent(bounds); based on that map zoom will change

Answer 1

Here's an example how you can parse WMS Capabilites with jQuery to get the bounding boxes and some other information about layers contained in the WMS:

var layers = [];    
$.ajax({
    type: "GET",
    url: yourWMSUrlHere,
    dataType: "xml",
    async: true
}).done(function (data) {        
    $(data).find('Layer').each(function (i, layer) {
        layer = $(layer);
        var name = layer.children("Name").text();
        if (name) {
            layers.push({
                name: name,
                title: layer.children("Title").text(),
                queryable: layer.attr('queryable'),
                minScale: layer.children("MaxScaleDenominator").text(),
                maxScale: layer.children("MinScaleDenominator").text(),
                xmin: layer.children('EX_GeographicBoundingBox').children('westBoundLongitude').text(),
                ymin: layer.children('EX_GeographicBoundingBox').children('southBoundLatitude').text(),
                xmax: layer.children('EX_GeographicBoundingBox').children('eastBoundLongitude').text(),
                ymax: layer.children('EX_GeographicBoundingBox').children('northBoundLatitude').text()
            });
        }
    });
});

Then you have to construct the bounds from xmin, ymin, xmax and ymax.

Answer 2

According to your question I think you want to apply bounding box control in map.

For that you need to :

1.add any layer and

2.use map.setCenter() property.

Please check this example for the reference & right click on that page and view source so that you insert your link in similar fashion.

hope this will help you..

Answer 3

It's not clear what you are trying to achieve. Normally, the bounds of a projection are defined as global, unless the projection is specialised, like UK's BNG where the coordinate system only covers the UK.

If you want to prevent the user panning outside a certain zone, then the thing to set is restrictedExtent.

However, there's no easy way to get this bounding box from the server. All I could think to do would be to have a hidden Vector layer, populate it from the server, and use the getDataExtent() method to extract a bounding box. However, it seems a bit messy and expensive.