define([     "dojo/_base/declare",     "dojo/_base/lang",     "esri/layers/DynamicMapServiceLayer",     "esri/geometry/Extent" ], function(     declare,     lang,     DynamicMapServiceLayer,     Extent ) {
      return declare("DynamicMapSuperPost", DynamicMapServiceLayer, { // create DynamicMapLayer by extending esri.layers.TiledMapServiceLayer         constructor:function(){
              this.spatialReference = new esri.SpatialReference({wkid:4490});             this.initialExtent = this.fullExtent = new Extent({"xmin":109.3868865977334,"ymin":29.938091498799054,"xmax":117.6127404019528,"ymax":37.81307950094276,"spatialReference": this.spatialReference});             this.loaded = true;             this.onLoad(this);         },         getImageUrl: function(extent, width, height, callback) {
              var params = {
                  //request: "GetMap",                 //transparent: true,                 format: "png",//"image/png",                 //bgcolor: "ffffff",                 //version: "1.1.1",                 layers: 'id1,id2,id3,id4',                 //styles: "default,default",                 //exceptions: "application/vnd.ogc.se_xml",                 //changing values                 bbox: extent.xmin + "," + extent.ymin + "," + extent.xmax + "," + extent.ymax,                 //bbox:'113.68330445912024,34.75990865047065,113.71526537935056,34.77527045072429',                 MAPID: 110,                 //GRAY:0,                 //LAYERHIDEOID:'`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^',                 //LAYERHIDEOID:'`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^`^',                 //srs: "EPSG:" + extent.spatialReference.wkid,                 width: width,                 height: height             };             var curParams = dojo.objectToQuery(params);             var _self = this;             var curentImgId = this._img_loading.id; 　　　　　　　//这个地方是使用了servlet返回动态层的png图片,原因是有些动态层是定制的，要符合他们要求             var url = '../proxy';             var xhr = new XMLHttpRequest();             xhr.responseType = 'blob';             xhr.open('POST', url, true);//POST请求，请求地址，是否异步             xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded')             xhr.onload = function (ev) {
                  if (this.status == 200) {
                      var data = this.response;                     var blob = new Blob();                     blob = data;                     var blobImage = window.URL.createObjectURL(blob);                     if (_self._img_loading && _self._img_loading.id == curentImgId) {
                          callback(blobImage);                     } else {//缩放或移动中img被arcgis删除了,丢失dom节点                         window.URL.revokeObjectURL(blobImage);//释放                     }                 }             }             xhr.send(curParams);         },         _imgSrcFunc: function (a) {
              this._img_loading.src = a             this._img_loading.onload = function () {
                  window.URL.revokeObjectURL(this.src);//释放             }         }     }); });