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。