MapServer Tutorial——MapServer7.2.1教程学习——第一节用例实践：Example1.3 Displaying Classes in a Layer

MapServer Tutorial——MapServer7.2.1教程学习——第一节用例实践：Example1.3 Displaying Classes in a Layer

一、前言

　　关于第一节的案例，分别介绍了一个基本的地图站点应用程序创建和多图层地图站点应用程序创建。这个案例主要来介绍一下mapfile文件中 LAYER 对象里面，CLASS对象的应用。

　　同时还有如何根据CLASSITEM、EXPRESSION等配置去修改地图的显示方式。

　　最后还有一个很酷炫的方法一次性读取shp文件中的数据信息。

　　当前案例官网：https://www.mapserver.org/tutorial/example1-3.html#example1-3

　　附带一点其他的，当前系列博客的大纲博文《MapServer Tutorial——MapServer7.2.1教程学习（大纲）》，我会持续更新。

　　以及我所写博文的应用环境《MapServer Configuring with IIS》。

　　希望能够给新手带来帮助。

二、创建Example1.3 Displaying Classes in a Layer站点

　　老规矩，按照先前的创建站点规则。

　　在cmd中输入：cd /d E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps

　　在cmd中输入：md Example1.3

　　在cmd中输入：cd Example1.3

　　在cmd中输入：md data

　　在cmd中输入：md logs

　　在cmd中输入：cd.>web.config

　　在cmd中输入：cd.>example1_3.map

　　红色标记路径部分，按照你站点创建位置填写。

　　修改web.config，内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <handlers>
            <add name="MapServerFastCgi" 
　　　　　　　　　　　　path="*" verb="*" type="" modules="FastCgiModule" 
　　　　　　　　　　　　scriptProcessor="E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\bin\mapserv.exe" 
　　　　　　　　　　　　resourceType="Unspecified" requireAccess="Script" allowPathInfo="false" preCondition=""  />
        </handlers>
        <caching enabled="true" enableKernelCache="true" />
    </system.webServer>
</configuration>

　　打开IIS创建站点，站点名称、应用程序池名称为：Example1.3。端口号：8013。

　　给应用程序池添加对logs文件夹的读写权限。

　　在cmd中输入：icacls "E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps\Example1.3\logs" /grant "IIS AppPool\Example1.3":(OI)(CI)RW

　　将states_ugl.dbf、states_ugl.shp、states_ugl.shx等文件复制到Example1.3中的data文件夹下面。

　　mapfile（example1_3.map）文件内容如下：

# The annotated map file (sort of)
# Created by Pericles S. Nacionales for the MapServer tutorial
# 20050408
#
# MapServer map file uses the pound sign (#) to denote the start of a line
# comment--each line that needs to be commented has to be prepended with a "#".
#
# Map files begin with MAP keyword to signify the start of the map object.
# Well, the entire map file is THE map object.  Enclosed between MAP and END
# at the very bottom of this map file, are keyword/value pairs and other
# objects.
MAP
  IMAGETYPE      PNG
  EXTENT         -97.238976 41.619778 -82.122902 49.385620
  SIZE           400 300
  SHAPEPATH      "./data"
  IMAGECOLOR     255 255 255

  # Layer objects are defined beneath the map object.  You need at least one
  # layer defined in your map file before you can display a map...  You can
  # define as many layers as you'd like although a limit is typically hard-coded
  # in map.h in the MapServer source.  The default limit is set at 100.  You'd
  # have to have a very specialized application to need more than 100 layers in
  # your application.

  # Start of LAYER DEFINITIONS ---------------------------------------------
  LAYER # States polygon layer begins here
    NAME         states_poly
    DATA         states_ugl
    STATUS       OFF
    TYPE         POLYGON

    # CLASSITEM defines the non-spatial attribute that you will be using to
    # separate a layer into classes.  This attribute will be in the DBF file
    # of your shapefile (it will be different for each data format).  In this
    # example the shapefile states_ugl has an associated database
    # (states_ugl.dbf) that contains an attribute called "CLASS".  You will be
    # using two values in the CLASS attribute to separate the classes (also
    # called themes) used in this layer--land and water.  CLASSITEM is used in
    # association with the EXPRESSION parameter in the CLASS object.  See below.
    CLASSITEM    "CLASS"

    # The class object is defined within the layer object.  You can define as
    # many classes as you need (well, there are limits as with layers, but it's
    # senseless to define more than ten on a "normal" layer.  There are
    # situations, however, where you might have to do it.)
    CLASS
      NAME 'States'
      EXPRESSION 'land' # Only polygons where "CLASS" = 'land' will be drawn.

      # There are styles in a class, just like there are classes in a layer,
      # just like there are layers in a map.  You can define multiple styles in
      # a class just as you can define multiple classes in a layer and multiple
      # layers in a map.
      STYLE
        COLOR      232 232 232
      END
    END
    CLASS
      NAME 'Water'
      EXPRESSION 'water' # Only polygons where "CLASS" = 'water' will be drawn.
      STYLE
        COLOR      198 198 255
      END
    END
  END # States polygon layer ends here

  LAYER # States line layer begins here
    NAME         states_line
    DATA         states_ugl
    STATUS       OFF
    TYPE         LINE

    CLASSITEM    "CLASS"
    CLASS
      NAME       'State Boundary'
      EXPRESSION 'land'
      STYLE
        COLOR    32 32 32
      END
    END
  END # States line layer ends here
  # End of LAYER DEFINITIONS -------------------------------
  DEBUG 5
  CONFIG "MS_ERRORFILE" "logs\ms.log"
END # All map files must come to an end just as all other things must come to...

　　在浏览器中输入：http://localhost:8013/mapserv?map=../apps/Example1.3/example1_3.map&layer=states_poly&layer=states_line&mode=map

　　URL参数解析通上一章《MapServer Tutorial——MapServer7.2.1教程学习——第一节用例实践：Example1.2 Static Map with Two Layers》相同，详见上一章URL参数解析。

　　同样的shp数据文件，只是mapfile文件不同，然后 polygon 区域的颜色就不同。这就是mapfile中CLASS对象的不同配置导致的。

三、MapFile文件解析

　　mapfile文件结构如下：

                            MAP
(states_poly) LAYER----------|---------LAYER (states_line)
               |                        |
(land) CLASS---|---CLASS (water)        |-CLASS
          |         |                      |
    STYLE-|         |-STYLE                |-STYLE

　　当前mapfile同样只有两个图层（layer），但是 polygon（NAME值为states_poly）的图层却有两个 CLASS 对象。其中 polygon 颜色的区分是通过：CLASSITEM、EXPRESSION等两个对象座椅区分的。

　　CLASSITEM

　　　　当一个layer使用多个CLASS时，CLASSITEM用于指定DBF文件（可理解为shp文件的数据库表）中，根据哪个属性（可理解为当前表的字段）去使用对应的CLASS。

　　　　当前案例 states_ugl.shp 文件有多个 polygon 区域，states_ugl.shp记录这个区域的矢量数据 polygon 所在区域、数量等。同时每个polygon还包含其他哪些属性。

　　　　但是，states_ugl.shp 中的 polygon 的其他属性数据在 states_ugl.dbf 文件里面。

　　　　打开cmd输入：cd /d E:\SvnWorkspace\LY_WEB_GIS\branches\Documents\ms4w-mapserver-for-wimdows\release-1911-x64-gdal-2-3-3-mapserver-7-2-1\apps\Example1.3\data

　　　　在cmd中输入：ogrinfo -al -so states_ugl.shp，查看当前shp文件的相关属性数据。数据如下：

INFO: Open of `states_ugl.shp'
      using driver `ESRI Shapefile' successful.

Layer name: states_ugl
Metadata:
  DBF_DATE_LAST_UPDATE=2002-03-07
Geometry: Polygon
Feature Count: 204
Extent: (-97.238976, 41.619778) - (-82.122902, 49.385620)
Layer SRS WKT:
(unknown)
AREA: Real (12.3)
PERIMETER: Real (12.3)
STATESP020: Integer64 (11.0)
STATE: String (20.0)
STATE_FIPS: String (2.0)
CLASS: String (5.0)

　　　　可以看到，shp的属性中包含一个叫做CLASS的属性。

　　　　在cmd中输入：ogrinfo -al -ro states_ugl.dbf 。可以查看当前shp文件的所有数据。

　　　　当然，输入：ogrinfo -al -ro states_ugl.shp也可以。因为目前案例中的数据文件是ESRI Shapefiles，所以最少包含三个文件，后缀名分别是：dbf、shp、shx，可以查看：https://www.mapserver.org/input/vector/format_types.html

　　　　相关命令查看：https://gdal.org/ogrinfo.html