javascript 获取 OpenLayers GET 请求的 responseText JSON 的元素
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Get element of a responseText JSON of an OpenLayers GET request
提问by Asma.O
I am trying to use OpenLayers.Request.GETto load data from url in JSON format.
我正在尝试使用OpenLayers.Request.GETJSON 格式从 url 加载数据。
Here's the request (note: url works fine, it brings data in JSON format):
这是请求（注意：url 工作正常，它以 JSON 格式提供数据）：
var request = OpenLayers.Request.GET({
url: "http://localhost:8080/geoserver/wrspc/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=wrspc:layer1&maxFeatures=60&outputFormat=json",
callback: handler
});
for the handler I tried to get the request.responseTextand show a specific key in the json file like this:
对于处理程序，我尝试获取request.responseText并在 json 文件中显示特定键，如下所示：
var obj;
function handler(request) {
obj = request.responseText;
alert (obj.features[0].indicator);
}
and here's my JSON:
这是我的 JSON：
{"type":"FeatureCollection","features":[{"type":"Feature","id":"titid","geometry":{"type":"MultiPolygon","coordinates":[[[[3694.7863290442,3749.0463695516],[9328.2052648721,3756.61081112875],[3694.18117371807,3861.9059202327],[9340.68659347435,3834.4171230714],[9334.7863290442,3749.0463695516],[3634.7863290442,3839.0463695516]]]]},"geometry_name":"the_geom","properties":{"name1":"asme","number":9130,"indicator":"20","gid":939}}],"crs":{"type":"EPSG","properties":{"code":"2684"}}}
but I get this error: (note the TestPrint.html:506 is the alert line)
但我收到此错误：（注意 TestPrint.html:506 是警报线）
Uncaught TypeError: Cannot read property '0' of undefined TestPrint.html:506
GeoExt.form.FormPanel.listeners.actioncomplete TestPrint.html:506
h.Event.fire ext-all.js:21
h.Observable.fireEvent ext-all.js:21
(anonymous function) ext-all.js:21
h.Event.fire ext-all.js:21
h.Observable.fireEvent ext-all.js:21
Ext.form.BasicForm.Ext.extend.afterAction ext-all.js:21
GeoExt.form.SearchAction.Ext.extend.handleResponse SearchAction.js:147
OpenLayers.Protocol.WFS.v1.OpenLayers.Class.handleRead OpenLayers.js:843
(anonymous function) OpenLayers.js:413
(anonymous function) OpenLayers.js:62
OpenLayers.Request.runCallbacks OpenLayers.js:509
d.onreadystatechange OpenLayers.js:508
b.dispatchEvent OpenLayers.js:751
c OpenLayers.js:744
_object.onreadystatechange OpenLayers.js:748
回答by Niccolò Campolungo
You don't parse your response, the function you need to use is JSON.parse:
您不解析您的响应，您需要使用的功能是JSON.parse：
function handler(request) {
//responseText is the raw JSON string, you need to convert it to a JS object
//use var keyword to define new variables inside your function scope
var obj = JSON.parse(request.responseText);
//note that indicator is not a valid features property, you should change it!
alert(obj.features[0].indicator); //return undefined, change it maybe to .type
}
Your error is given by your attempt to access "all your JSON".featureswhich is undefined(have you ever heard about a string that has featuresproperty(it should be a list)? I don't really think so :P
您的错误是由于您尝试访问“所有您的 JSON”。未定义的功能（您是否听说过具有features属性的字符串（它应该是一个列表）？我真的不这么认为：P
回答by Aragon
you can reach your "indicator" object with following way(it is nested under properties feature):
您可以通过以下方式访问您的“指标”对象（它嵌套在属性功能下）：
obj.features[0].properties['indicator']
in such cases you can use online json parserfor understanding your json structure.
在这种情况下，您可以使用在线 json 解析器来了解您的 json 结构。
your json:
你的json：
{
"type":"FeatureCollection",
"features":[
{
"type":"Feature",
"id":"titid",
"geometry":{
"type":"MultiPolygon",
"coordinates":[
[]
]
},
"geometry_name":"the_geom",
"properties":{
"name1":"asme",
"number":9130,
"indicator":"20",
"gid":939
}
}
],
"crs":{
"type":"EPSG",
"properties":{
"code":"2684"
}
}
}
回答by Asma.O
I figured it out, now it works with the evalfunction,
我想通了，现在它可以与该eval功能一起使用，
obj = eval('(' + request.responseText + ')');
and with alert(obj.features[0].properties['indicator']);.
并与alert(obj.features[0].properties['indicator']);。
