openlayers中获得geojson格式数据

function getGeoJson(layerName){
//layerName="TJDG:PipePoint",
var parr = {
REQUEST: "GetFeature",
typeName:layerName,
SERVICE: "WFS",
version:'1.0.0',
request:'GetFeature',
outputFormat:"json",
maxFeatures:1000
};
OpenLayers.loadURL("http://localhost:8080/geoserver/TJDG/ows", parr, this, succ, faill);
function succ(response){
var gmlParse = new OpenLayers.Format.GML();
alert(response.responseText);
}
function faill(response){
alert("无数据");
}
}