从本地服务器上的文件读取XML或JSON

我试图从XML文件或JSON文件加载在谷歌地图中使用的坐标列表(我都在本地测试服务器上的同一目录中托管)。到目前为止，我已经使用硬编码的JSON对象来加载要测试的地图坐标。我的问题是，如何用服务器上的XML/JSON文件替换假/硬编码JSON ?下面是我的代码:

  (function() {
  // Creating an array that will contain all of our product icons
  var productIcons = [];
  productIcons['bulletin'] = new google.maps.MarkerImage(
    'icons/Bulletin-sm.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );
  productIcons['bus'] = new google.maps.MarkerImage(
    'icons/busicon.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );
  productIcons['bench'] = new google.maps.MarkerImage(
    'icons/BusBench-sm.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );
  productIcons['junior'] = new google.maps.MarkerImage(
    'icons/JuniorPoster-sm.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );
  productIcons['poster'] = new google.maps.MarkerImage(
    'icons/Poster-sm.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );

  productIcons['shelter'] = new google.maps.MarkerImage(
    'icons/TransitShelter-sm.png', 
    new google.maps.Size(48, 48), 
    null, 
    new google.maps.Point(24, 24)
  );
  window.onload = function() {
    // Creating a map
    var options = {  
      zoom: 3,  
      center: new google.maps.LatLng(37.09, -95.71),  
      mapTypeId: google.maps.MapTypeId.ROADMAP  
    };  
    var map = new google.maps.Map(document.getElementById('map'), options);  

// Creating a JSON object with fake product data (to be replaced by XML or JSON)
var productData = {'product': [
{
'lat': 40.756054,
'lng': -119.986951,
'productType': 'junior'
},
{
'lat': 35.620973,
'lng': -121.347276,
'productType': 'shelter'
},
{
'lat': 40.620973,
'lng': -121.347276,
'productType': 'bus'
},
{
'lat': 39.120973,
'lng': -122.847276,
'productType': 'bench'
},
{
'lat': 35.920973,
'lng': -122.347276,
'productType': 'bulletin'
},
{
'lat': 37.775206,
'lng': -122.419209,
'productType': 'poster'
}
]};
// Looping through the product array in productData
for (var i = 0; i < productData.product.length; i++) {
// creating a variable that will hold the current product object
var product = productData.product[i];
// Creating marker
var marker = new google.maps.Marker({
position: new google.maps.LatLng(product.lat, product.lng),
map: map,
icon: productIcons[product.productType]
});
}
}
})();