采用开源软件搭建WebGIS系统（8）遇到困难，决定试一试WFS

今天会用TextSymbolizer来显示文字。

数据源geo_first_class_city_point 结构如下：

gid:  int
area:  double
perimeter:  double
res1_4m_:  long
res1_4m_id:  long
gbcode:  int
name:  string
adcode93:  int
adcode99:  int
adclass:  int
pinyin:  string
the_geom:  pointProperty
 
该层所采用的sld文件：

     < FeatureTypeStyle >
       < FeatureTypeName > feature </ FeatureTypeName >
       < Rule >
         < TextSymbolizer >
             < Geometry >
                 < ogc:PropertyName > the_geom </ ogc:PropertyName >
             </ Geometry >
             < Label >
                 < ogc:PropertyName > name </ ogc:PropertyName >
             </ Label >
             < Font >
                 < CssParameter  name ="font-family" > 宋体 </ CssParameter >
                 < CssParameter  name ="font-style" > italic </ CssParameter >
                 < CssParameter  name ="font-Size" >
                     < literal > 10 </ literal >
                 </ CssParameter >
             </ Font >
             < LabelPlacement >
                 < PointPlacement >
                     < AnchorPoint >
                         < AnchorPointX > 0 </ AnchorPointX >
                         < AnchorPointY > 0 </ AnchorPointY >
                     </ AnchorPoint >
                 </ PointPlacement >
             </ LabelPlacement >
             < Fill >
                 < CssParameter  name ="fill" > #000000 </ CssParameter >
             </ Fill >
             < Halo />
         </ TextSymbolizer >
         < PointSymbolizer >
         < Geometry >
             < ogc:PropertyName > the_geom </ ogc:PropertyName >
         </ Geometry >
             < graphic >
                 < size > 6 </ size >
                 < mark >
                     < wellknownname > circle </ wellknownname >
                     < Fill >
                         < CssParameter  name ="fill" > #FF0000 </ CssParameter >
                         < CssParameter  name ="fill-opacity" > 0.8 </ CssParameter >
                     </ Fill >
                 </ mark >
             </ graphic >
         </ PointSymbolizer >
     </ Rule >
     </ FeatureTypeStyle >

这里就不一项项解释上面各项含意了。不清楚的话请看OGC SLD规范。

得到图：

现在文字出来了，就是不好看。要弄好看点，可能需要进行坐标变换。看了看geoserver文档，当前geoserver对坐标变换支持不够。那怎么办呢？干脆通过WFS把数据调到客户端，到时候想怎么办就怎么办，想怎么显示就怎么显示，还可以加上超链接。


WFS调用格式举例如下：

http://localhost/geoserver/wfs/GetFeature?typeName=geo_first_class_city_point&BBOX=97.11500000000001,27.5225,119.11500000000001,44.5225

typeName就是你的数据层的名字，BBOX是查询范围。返回结果：

 

  <? xml version="1.0" encoding="UTF-8"  ?>  
-  < wfs:FeatureCollection  xmlns:wfs ="http://www.opengis.net/wfs"  xmlns:topp ="http://www.openplans.org/topp"  xmlns:gml ="http://www.opengis.net/gml"  xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"  xsi:schemaLocation ="http://www.openplans.org/topp http://localhost:80/geoserver/wfs/DescribeFeatureType?typeName=topp:geo_first_class_city_point http://www.opengis.net/wfs http://localhost:80/geoserver/data/capabilities/wfs/1.0.0/WFS-basic.xsd" >
-  < gml:boundedBy >
-  < gml:Box  srsName ="http://www.opengis.net/gml/srs/epsg.xml#4326" >
   < gml:coordinates  decimal ="."  cs =","  ts ="" > 101.7874527,28.20082474 118.77278137,40.82094193 </ gml:coordinates >  
   </ gml:Box >
   </ gml:boundedBy >
-  < gml:featureMember >
-  < topp:geo_first_class_city_point  fid ="geo_first_class_city_point.83613" >
   < topp:gid > 0 </ topp:gid >  
   < topp:area > 0.0 </ topp:area >  
   < topp:perimeter > 0.0 </ topp:perimeter >  
   < topp:res1_4m_ > 1 </ topp:res1_4m_ >  
   < topp:res1_4m_id > 61 </ topp:res1_4m_id >  
   < topp:gbcode > 31010 </ topp:gbcode >  
   < topp:name > 北京 </ topp:name >  
   < topp:adcode93 > 110100 </ topp:adcode93 >  
   < topp:adcode99 > 110100 </ topp:adcode99 >  
   < topp:adclass > 1 </ topp:adclass >  
   < topp:pinyin > Beijing </ topp:pinyin >  
-  < topp:the_geom >
-  < gml:Point  srsName ="http://www.opengis.net/gml/srs/epsg.xml#4326" >
   < gml:coordinates  decimal ="."  cs =","  ts ="" > 116.3809433,39.9236145 </ gml:coordinates >  
   </ gml:Point >
   </ topp:the_geom >
   </ topp:geo_first_class_city_point >
   </ gml:featureMember >
-  < gml:featureMember >
    ……
   </ gml:featureMember >
   </ wfs:FeatureCollection >

这样我可以在客户端解析wfs返回的数据，想怎么显示怎么显示。

实际上Geoserver+Geotools已经实现了大部分webgis的功能，只要理解了OGC规范，不难开发出复杂的应用。