转自：http://blog.csdn.net/mach365/archive/2011/01/19/6151827.aspx
说到实时监控,我们不能不承认Openlayers功能的确非常强大。Openlayers中通过很多方式都能实现实时监控。我讲讲我的实现方式。
我的方式很简单：页面发起异步请求;服务端程序将请求结果处理成GeoJSON串回传至请求页面;请求页面通过OpenLayers提供的OpenLayers.Format.GeoJSON解析GeoJSON串，将结果展现到地图上。
下面的示例显示:实时获得油机的位置数据,展示到页面上。
页面程序:
view plain copy to clipboard print ? //初始地图 function init(){ ...... vectors = new OpenLayers.Layer.Vector(...); geojson = new OpenLayers.Format.GeoJSON(); map.addLayer(vectors); } //通过DWR异步取得GeoJSon串,交由OpenLayers.Format.GeoJSON来处理. function locorie(){ //异步发出请求 dwrService.orie(orieSeri,function(data){ //通过OpenLayers.Format.GeoJSON处理服务端提供的GenJSon串 var features = geojson.read(data,"FeatureCollection"); if(features) { //将结果展示到地图上 vectors.addFeatures(features); } }); } //十秒更新一次数据 function startOrie(){ var t=setTimeout("locorie();startOrie();",10000); }
//初始地图 function init(){ ...... vectors = new OpenLayers.Layer.Vector(...); geojson = new OpenLayers.Format.GeoJSON(); map.addLayer(vectors); } //通过DWR异步取得GeoJSon串,交由OpenLayers.Format.GeoJSON来处理. function locorie(){ //异步发出请求 dwrService.orie(orieSeri,function(data){ //通过OpenLayers.Format.GeoJSON处理服务端提供的GenJSon串 var features = geojson.read(data,"FeatureCollection"); if(features) { //将结果展示到地图上 vectors.addFeatures(features); } }); } //十秒更新一次数据 function startOrie(){ var t=setTimeout("locorie();startOrie();",10000); }
服务端程序:
view plain copy to clipboard print ? public String[] orie(String orieSeri) { String orieStr = ""; boolean state = true; if (null == orieStr || "".equals(orieSeri)) { state = false; } int dataSeri = Integer.parseInt(orieSeri); List<Location> list = null; if (state) { // 获得dataSeri之后的位置数据 Location.getDataSeri >= dataSeri list = locDao.findLocByFlow(dataSeri); } if (state && (list == null || list.size() == 0)) { // 没有数据 state = false; } if (state&&(list.size() == 1 && dataSeri == list.get(0).getDataSeri() .intValue())) { // 没有新的数据 state = false; } if (state) { LineString line = new LineString(); StringBuffer geo = new StringBuffer(); Point pointEnd = new Point(); Feature feaPoint = new Feature(pointEnd); Map<String, String> propoint = new HashMap<String, String>(); feaPoint.setProperties(propoint); for (int i = 0; i < list.size(); i++) { geo.append("[" + list.get(i).getCurLoc() + "]"); if (i != (list.size() - 1)) { geo.append(","); } } line.setLine(geo.toString()); Feature feaLine = new Feature(line); Map<String, String> properties = new HashMap<String, String>(); properties.put("color", "#1A60CA"); feaLine.setProperties(properties); List<Component> components = new ArrayList<Component>(); components.add(feaLine); components.add(feaPoint); FeatureCollection feaCol = new FeatureCollection(components); orieStr = feaCol.draw(); } }
public String[] orie(String orieSeri) { String orieStr = ""; boolean state = true; if (null == orieStr || "".equals(orieSeri)) { state = false; } int dataSeri = Integer.parseInt(orieSeri); List<Location> list = null; if (state) { // 获得dataSeri之后的位置数据 Location.getDataSeri >= dataSeri list = locDao.findLocByFlow(dataSeri); } if (state && (list == null || list.size() == 0)) { // 没有数据 state = false; } if (state&&(list.size() == 1 && dataSeri == list.get(0).getDataSeri() .intValue())) { // 没有新的数据 state = false; } if (state) { LineString line = new LineString(); StringBuffer geo = new StringBuffer(); Point pointEnd = new Point(); Feature feaPoint = new Feature(pointEnd); Map<String, String> propoint = new HashMap<String, String>(); feaPoint.setProperties(propoint); for (int i = 0; i < list.size(); i++) { geo.append("[" + list.get(i).getCurLoc() + "]"); if (i != (list.size() - 1)) { geo.append(","); } } line.setLine(geo.toString()); Feature feaLine = new Feature(line); Map<String, String> properties = new HashMap<String, String>(); properties.put("color", "#1A60CA"); feaLine.setProperties(properties); List<Component> components = new ArrayList<Component>(); components.add(feaLine); components.add(feaPoint); FeatureCollection feaCol = new FeatureCollection(components); orieStr = feaCol.draw(); } }
服务器端提供的数据格式如下:
view plain copy to clipboard print ? //一条线 { "type":"FeatureCollection", "features":[{ "type":"Feature", "geometry":{ "type":"LineString", "coordinates":[[42.895131111145, 22.148587703705],[43.895131111145, 23.148587703705]]}}] }
//一条线 { "type":"FeatureCollection", "features":[{ "type":"Feature", "geometry":{ "type":"LineString", "coordinates":[[42.895131111145, 22.148587703705],[43.895131111145, 23.148587703705]]}}] }
服务器端生成json串，我用装饰者模式写了一个模块，只要调用这个模块的API就会生成需要的Json串。
服务端生成GeoJSon的jar源文件下载位置。 http://download.csdn.net/source/2991502
