openlayers加载arcgis server的wms服务，getMap接口如何使用post请求？是否支持POST？

let lyr3 = new ol.layer.Image({

    source: new ol.source.ImageWMS({

        url: '********/MapServer/WmsServer',

        params: {

            VERSION: '1.1.0',

            LAYERS: '4',

            SRS: 4490

        },

        imageLoadFunction:function(){

            // 这里面使用post请求

        }

    })

})

<ServiceExceptionReport version="1.1.1">

<ServiceException code="InvalidFormat">

     Can't parse XML request.

</ServiceException>