javascript - How to force EXT JS - GeoEXT to show legends with OpenLayers?

My sld is applying as below

  function cusMap(strSld_body,talukaName,name){
       console.log(strSld_body);

    var query = new OpenLayers.Layer.WMS.Post(name,  
    geoServerURL, {
        LAYERS : 'VP:village_customize',
        sld_body : strSld_body,
        format : 'image/jpeg',
        transparent : 'true'
    },
    {
        unsupportedBrowsers: [],
        isBaseLayer: false,

        yx : {'EPSG:4326' : true}
    } );
  query.mergeNewParams({'CQL_FILTER': "Taluka='"+talukaName+"'"});
  query.mergeNewParams({'sld_body': strSld_body});
  query=registerEvents(query);
   map.addLayer(query);

 }

But the legend is not coming as per sld made. How can I force legends to show up?

I am using Ext JS Tree to show legends.

 Ext.onReady(function() {

var mapPanel = new GeoExt.MapPanel({
    renderTo : 'mymap',
    width:780,
    zoom:7,
    region: "center",
    //autoWidth:true,
    boxMaxWidth : 762,

    boxMaxHeight : 490,
    map: map
    //layout: "fit"       

});

var tree = new Ext.tree.TreePanel({
    renderTo : 'mytree',
    region: "east",
    title: "Layers / Legends",


    width: 230,
    boxMaxHeight : 455,

    autoScroll: true,
    enableDD: true,
    collapsible: false,
    split: false,

    plugins: [{

            ptype: "gx_treenodecomponent"
        }],
    loader: {
        applyLoader: true,
        uiProviders: {
            "custom_ui": LayerNodeUI
        }
    },
    root: {
        nodeType: "gx_layercontainer",

        loader: {
            baseAttrs: {
                uiProvider: "custom_ui"

            },
            createNode: function(attr) {
                // add a WMS legend to each node created
                attr.component = {
                    xtype: "gx_wmslegend",
                    layerRecord: mapPanel.layers.getByLayer(attr.layer),

                    showTitle: false,
                    cls: "legend"
                }
                return GeoExt.tree.LayerLoader.prototype.createNode.call(this, attr);
            }
        }
    },
    rootVisible: false,
    lines: true
});


new Ext.Viewport({
    layout: 'border',
    region: 'center',
    autoScroll: true,

    split: false,
    renderTo : 'bodypanel',
            items: [
                  mapPanel,tree


            ]


});

});