Openlayers3 请求Geoserver带Filter的WFS查询

//TODO WFS 查询要素TEST

var vectorSource = new ol.source.Vector();
var vector = new ol.layer.Vector({
source: vectorSource,
style: new ol.style.Style({
stroke: new ol.style.Stroke({
color: 'rgba(0, 0, 255, 1.0)',
width: 2
})
})
});
map.addLayer(vector);

// generate a GetFeature request
var featureRequest = new ol.format.WFS().writeGetFeature({
srsName: 'EPSG:3857',
featureNS: 'http://www.ztbr.com',    //命名空间
featurePrefix: 'zbtr',               //工作区域
featureTypes: ['yanqing18jd'],       //图层名
outputFormat: 'application/json',
filter:
ol.format.filter.equalTo('街道', '百泉街道')    //todo 条件查询过滤
});

// then post the request and add the received features to a layer
fetch('http://localhost:8082/geoserver/wfs', {
method: 'POST',
body: new XMLSerializer().serializeToString(featureRequest)
}).then(function(response) {
return response.json();
}).then(function(json) {
var features = new ol.format.GeoJSON().readFeatures(json);
vectorSource.addFeatures(features);
map.getView().fit(vectorSource.getExtent());
});