GeoWebCache的配置与使用
最近在做一个开源GIS的demo的工作，工作中涉及到了地图瓦片，选取的开发环境是geoserver+openlayers，那么地图瓦片自然而然也就使用geowebcache，geowebcache就相当于是openlayer和geoserver之间的中介，首先，geowebcache会根据你的配置信息，把相应的地图图层切好图，存放在磁盘中，然后在使用openlayer加载地图服务的时候，把地图服务的地址指向geowebcache，geowebcache接收到这些请求后，会根据请求的位置和比例尺在切片目录中找到对应的瓦片，然后返回给你，省去了动态生成地图的过程，速度大幅度提高，而且由于请求的图片资源是事先生成好的，浏览器加载这些图片之后，下一次再去请求同样的图片，就会从浏览器的缓存中拉去，速度进一步提高！
下面说一下geowebcache的配置使用。首先下载war包，在tomcat中解压后，会在WEB-INF目录下找到一系列配置文件，先找到web.xml，然后在web-app根元素下添加：
<context-param>
<param-name>GEOWEBCACHE_CACHE_DIR</param-name>
<param-value>D:/data/cache</param-value>
</context-param>
param-value的值就是你要存放geowebcache瓦片的位置，配置好这里，重启tomcat，你会发现在你的瓦片目录下生成了一些文件，其中就有geowebcache.xml，这个文件是geowebcache配置的关键所在，以下是这个文件的配置信息：
<?xml version="1.0" encoding="utf-8"?>
<gwcConfiguration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://geowebcache.org/schema/1.5.3"
xsi:schemaLocation="http://geowebcache.org/schema/1.5.3 http://geowebcache.org/schema/1.5.3/geowebcache.xsd">
<version>1.5.3</version>
<backendTimeout>120</backendTimeout>
<serviceInformation>
<title>GeoWebCache</title>
<description>GeoWebCache is an advanced tile cache for WMS servers.It supports a large variety of protocols and
formats, including WMS-C, WMTS, KML, Google Maps and Virtual Earth.</description>
<keywords>
<string>WFS</string>
<string>WMS</string>
<string>WMTS</string>
<string>GEOWEBCACHE</string>
</keywords>
<serviceProvider>
<providerName>lzugis</providerName>
<providerSite>http://blog.csdn.net/gisshixisheng</providerSite>
<serviceContact>
<individualName>lzugis</individualName>
<positionName>GIS工程师</positionName>
<addressType>工程师</addressType>
<addressStreet>海淀区翠微路甲3号</addressStreet>
<addressCity>北京</addressCity>
<addressAdministrativeArea>海淀区</addressAdministrativeArea>
<addressPostalCode>010010</addressPostalCode>
<addressCountry>中国,China</addressCountry>
<phoneNumber>+81 189 1133 7984</phoneNumber>
<faxNumber>+81 189 1133 7984</faxNumber>
<addressEmail>[email protected]</addressEmail>
</serviceContact>
</serviceProvider>
<fees>NONE</fees>
<accessConstraints>NONE</accessConstraints>
</serviceInformation>
<gridSets>
<!-- Grid Set Example, by default EPSG:900913 and EPSG:4326 are defined -->
<gridSet>
<!-- This does not have to be an EPSG code, you can also have multiple gridSet elements per SRS -->
<name>EPSG:4326</name>
<srs>
<number>4326</number>
</srs>
<extent>
<coords>
<double>73.45100463600005</double>
<double>18.16324718800007</double>
<double>134.976797647</double>
<double>53.53194315200005</double>
</coords>
</extent>
<scaleDenominators>
<double>25000000</double>
<double>1000000</double>
<double>100000</double>
<double>25000</double>
</scaleDenominators>
<tileHeight>256</tileHeight>
<tileWidth>256</tileWidth>
</gridSet>
</gridSets>
<layers>
<wmsLayer>
<name>china</name>
<mimeFormats>
<string>image/gif</string>
<string>image/jpeg</string>
<string>image/png</string>
<string>image/png8</string>
</mimeFormats>
<wmsUrl>
<string>http://200.200.200.220:8888/geoserver/wms</string>
</wmsUrl>
<wmsLayers>geoserver:china</wmsLayers>
</wmsLayer>
</layers>
</gwcConfiguration>
配置好上面的信息之后，进入：http://localhost:8080/geowebcache/demo，点击"
Reload Configuration
"重新读取配置信息,如下所示：
如果配置信息没错，你会发现，你所配置的图层信息已经显示在这个页面上了，点击“Seed this layer”，然后你需要输入下面这些信息：
设置好，点submit就开始切图了。在资源管理器中打开，如下图：
配置完成以后，就是如何在地图中显示了，下面是显示的源代码：
<pre name="code" class="html"><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>china EPSG:4326 image/png</title>
<link rel="stylesheet" type="text/css" href="http://200.200.200.220/OpenLayers-2.12/theme/default/style.css"/>
<style type="text/css">
body { font-family: sans-serif; font-weight: bold; font-size: .8em; }
body { border: 0px; margin: 0px; padding: 0px; }
#map { width: 100%; height: 100%; border: 0px; padding: 0px; }
</style>
<script type="text/javascript" src="http://200.200.200.220/OpenLayers-2.12/OpenLayers.js"></script>
<script type="text/javascript" src="http://200.200.200.220/OpenLayers-2.12/lib/OpenLayers/Lang/zh-CN.js"></script>
<script type="text/javascript">
var map, demolayer;
OpenLayers.DOTS_PER_INCH = 90.71428571428572;
OpenLayers.Util.onImageLoadErrorColor = 'transparent';
function init(){
var mapOptions = {
resolutions: [0.703125, 0.3515625, 0.17578125, 0.087890625, 0.0439453125, 0.02197265625,
0.010986328125, 0.0054931640625, 0.00274658203125, 0.001373291015625, 6.866455078125E-4,
3.4332275390625E-4, 1.71661376953125E-4, 8.58306884765625E-5, 4.291534423828125E-5,
2.1457672119140625E-5, 1.0728836059570312E-5, 5.364418029785156E-6, 2.682209014892578E-6,
1.341104507446289E-6, 6.705522537231445E-7, 3.3527612686157227E-7
],
projection: new OpenLayers.Projection('EPSG:4326'),
maxExtent: new OpenLayers.Bounds(-180.0,-90.0,180.0,90.0),
units: "degrees",
controls: []
};
map = new OpenLayers.Map('map', mapOptions );
map.addControl(new OpenLayers.Control.PanZoomBar({
position: new OpenLayers.Pixel(2, 15)
}));
map.addControl(new OpenLayers.Control.Navigation());
map.addControl(new OpenLayers.Control.Scale($('scale')));
map.addControl(new OpenLayers.Control.MousePosition({element: $('location')}));
demolayer = new OpenLayers.Layer.WMS(
"china","http://200.200.200.220:8080/geowebcache/service/wms",
{layers: 'china', format: 'image/png' },
{ tileSize: new OpenLayers.Size(256,256)}
);
map.addLayer(demolayer);
map.zoomToExtent(new OpenLayers.Bounds(73.45100463600005, 18.16324718800007,
134.976797647, 53.53194315200005)
);
}
</script>
</head>
<body onLoad="init()">
<div id="map"></div>
</body>
</html>
显示的结果如下：
附件：
geowebcache-1.5.3-war.zip
或者我的百度网盘，地址：http://pan.baidu.com/s/1kTJt91l