如何将json对象从java传递给javascript？
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how to pass json object from java to javascript?
提问by user1199476
I'm trying to pass data from spring controller to javascript but with no luck. Should I use ajax to do this? Please could you give me some hints on how do this? What is the best way?
我正在尝试将数据从 spring 控制器传递给 javascript，但没有运气。我应该使用ajax来做到这一点吗？请你能给我一些关于如何做到这一点的提示吗？什么是最好的方法？
In my controller I try to pass data:
在我的控制器中，我尝试传递数据：
@RequestMapping(value = "/map", method = RequestMethod.GET)
public String map(ModelMap model) {
...
model.addAttribute("trackpoints", json);
return "map";
}
where json is a gson object (JsonObject) containing:
其中 json 是一个 gson 对象 (JsonObject)，其中包含：
{"trackpoints":[{"latitude":52.390556,"longitude":16.920295},
{"latitude":52.390606,"longitude":16.920262}]}
in my jsp file I have:
在我的jsp文件中，我有：
<script type="text/javascript">
var myJSON = {};
myJSON = ${trackpoints};
document.writeln(myJSON.trackpoints);
</script>
but the result is:
但结果是：
[object Object],[object Object]
I explain this in more detail: >
我更详细地解释了这一点：>
i want use google maps api to display map and draw path coordinated from many lat,longs. i reckon json will be better than list, but i can be wrong.
我想使用谷歌地图 api 来显示地图并绘制从许多经纬度协调的路径。我认为 json 会比列表更好，但我可能是错的。
i try to adjust code from documentation - in code below i try to replace hardcoded coordinates with loop, and values from json object.
我尝试从文档中调整代码 - 在下面的代码中，我尝试用循环替换硬编码坐标，以及来自 json 对象的值。
<script type="text/javascript">
function initialize() {
var myLatLng = new google.maps.LatLng(0, -180);
var myOptions = {
zoom : 3,
center : myLatLng,
mapTypeId : google.maps.MapTypeId.TERRAIN
};
var map = new google.maps.Map(document.getElementById("map_canvas"),
myOptions);
var flightPlanCoordinates = [
new google.maps.LatLng(37.772323, -122.214897),
new google.maps.LatLng(21.291982, -157.821856),
new google.maps.LatLng(-18.142599, 178.431),
new google.maps.LatLng(-27.46758, 153.027892) ];
var flightPath = new google.maps.Polyline({
path : flightPlanCoordinates,
strokeColor : "#FF0000",
strokeOpacity : 1.0,
strokeWeight : 2
});
flightPath.setMap(map);
}
</script>
i hope it's now more clear:)
我希望现在更清楚了:)
回答by jabu.10245
myJSON.trackpointsis an array of two objects. If you want to write it as HTML you could do something like this:
myJSON.trackpoints是两个对象的数组。如果你想把它写成 HTML，你可以这样做：
function writeCoordinates(coords) {
document.writeln('<div>lat = ' + coords.latitude);
document.writeln(', lon = ' + coords.longitude + '</div>');
}
int len = myJSON.trackpoints.length;
for (int i = 0; i < len; i++) {
writeCoordinates(myJSON.trackpoints[i]);
}
BTW: JSON is really useful when you're using AJAX requests, but for "normal" requests it's better to put plain Java objects into the model, for example:
顺便说一句：当您使用 AJAX 请求时，JSON 非常有用，但对于“普通”请求，最好将普通 Java 对象放入模型中，例如：
Spring Controller:
弹簧控制器：
List<Coordinate> trackpoints = ...
model.addAttribute("trackpoints", trackpoints);
JSP:
JSP:
<c:forEach items="${trackpoints}" var="coord">
<div>lat = ${coord.latitude}, lon = ${coord.longitude}</div>
</c:forEach>
given, that the Coordinateclass has the methods getLatitude()and getLongitude(). That method in the Spring controller can even be used for both "normal" and AJAX requests, by using a JSON encoder, like Hymanson, and the ContentNegotiatingViewResolver.
给定，Coordinate该类具有方法getLatitude()和getLongitude()。通过使用 JSON 编码器（如Hymanson）和ContentNegotiatingViewResolver，Spring 控制器中的该方法甚至可以用于“普通”和 AJAX 请求。
回答by Jeff Woodard
Take a look at: http://jsfiddle.net/AHue8/4/
看看：http: //jsfiddle.net/AHue8/4/
I guess the take-away here is that you need to specify which element in the trackpoint object you want and you countrol how those are displayed in the browser. Since a "trackPoint" isn't a primitive data type (it's an object with 2 data elements latitude and longitude), the browser doesn't know how to interpret it, so you have to tell it how.
我想这里的要点是您需要指定您想要的 trackpoint 对象中的哪个元素，并计算这些元素在浏览器中的显示方式。由于“trackPoint”不是原始数据类型（它是具有 2 个数据元素纬度和经度的对象），浏览器不知道如何解释它，因此您必须告诉它如何解释。
