WMS BBOX in URL vs in params

Question

I'm new to OpenLayers and GeoServer and I have a problem (of course :P). I must retrieve a layer from a GeoServer WMS service, and I want to construct the URL to request it. If I try to make this:

map.addLayer(new OpenLayers.Layer.WMS("test", 
    "http://192.168.0.30:8080/geoserver/dsn/wms?service=WMS&version=1.1.1&request=GetMap&BBOX="+map.getExtent().toBBOX()+"&srs=EPSG:900913",
    { layers: "area", transparent: true, format: 'image/png' })
);

all the tiles of the grid of the WMS are the same (I see a sort of periodic repetition of the image) but if I do

map.addLayer(new OpenLayers.Layer.WMS("test", 
    "http://192.168.0.30:8080/geoserver/dsn/wms?service=WMS&version=1.1.1&request=GetMap",
    { bbox:map.getExtent().toBBOX(), srs:"EPSG:900913", layers: "area", transparent: true, format: 'image/png' })
);

everything is working as expected.

What am I doing wrong in constructing the URL?

Answer 1

The first code example you supply is not the correct way to request a WMS layer in OpenLayers - you are providing unnecessary WMS parameters. The url should only be

http://192.168.0.30:8080/geoserver/dsn/wms

The rest of the parameters you are including are redundant because they are created by OpenLayers in the process of generating the WMS request. The bounding box in particular should not be specified. Openlayers will calculate the correct bounding box for each tile. I suspect the second code example is working only because OpenLayers is ignoring your bounding box parameter. (I assume you want a tiled layer. If not, there is a singleTile:true parameter you can add.)

Answer 2

I would also write the URL as "http://192.168.0.30:8080/geoserver/dsn/wms?" and give other useful parameters like shown in this post.

I didn't test it in OpenLayers but I wrote this way in Leaflet and it worked.