Kml导出教程

概述：基于PostGis生成Kml坐标文本，自定义样式

Kml文件结构说明

    
        小班kml
        
            小班kml
            
                吾古村-吾古村-00073001
                
                119.839503088405806,28.52349172528816 119.83935538293224,28.523463182087585 119.839117657947071,28.523367408901901 119.838750213745683,28.523252379716112 119.83844752877728,28.52321382391656 119.837960832848708,28.523308738368584 119.837605123227988,28.523429082395744 119.837592766430291,28.5235473680601 119.837585853618194,28.523666223064112 119.837572132516428,28.52383855792672 119.837598866124551,28.523957451497868 119.837726701857392,28.523969490966056 119.837901669576723,28.523963757042466 119.838063205691796,28.523940176265207 119.838231407017389,28.523958206173443 119.838338993601155,28.524011822241068 119.838513834565077,28.524089292158337 119.838634932712864,28.52410726556861 119.838769677779482,28.524000448998653 119.838944790022936,28.523899622959494 119.839059349410292,28.52379278216566 119.839167123175216,28.52372159227631 119.83932207467349,28.523602912356711 119.839423110918162,28.523537658750456 119.839503088405806,28.52349172528816
            
        
    

其中文档主体结构可拆分为 Document->Folder->Placemark，各层级之间为包含关系
其中Placemark为最小矢量单元，其中name为该要素名称，Style为样式，MultiGeometry为矢量图形坐标

使用PostGis导出矢量坐标

SELECT
      t1.cunname || '-' || t1.lb_name || '-' || t1.xiao_ban AS name,
      ST_ASKML(t1.geom) AS kml
FROM filter_sxc t1

image-20220422114649224.png

样式说明

color中样式为十六进制（abgr）

导出工具类

package com.dinnovate.ldysf.util;

import java.util.List;

/**
 * kml导出工具类
 * @author yangkun
 * @createTime 2022年04月19日 21:19:00
 */
public class KmlUtil {

    public static Integer COLOR_GREEN = 1;

    public static Integer COLOR_RED = 2;

    public static Integer COLOR_BLUE = 3;

    /**
     * 构造style
     * @param color
     * @return
     */
    public static String getStyle(Integer color){
        String style = "";
        if(color.equals(COLOR_RED)){
            style = "\t\t\t\t";
        }else if(color.equals(COLOR_GREEN)){
            style = "\t\t\t\t";
        }else if(color.equals(COLOR_BLUE)){
            style = "\t\t\t\t";
        }
        return style;
    }

    /**
     * 构造placemark
     * @author yangkun
     * @date 2022/4/22 11:00
     * @param name:
     * @param kml:
     * @param color:
     * @return: java.lang.String
    **/
    public static String getPlacemark(String name,String kml,Integer color){
        String style = getStyle(color);
        String placemark = "\t\t\t\n"
            + "\t\t\t\t%s\n"
            + "%s\n"
            + "\t\t\t\t%s\n"
            + "\t\t\t\n";
        placemark = String.format(placemark, name,style,kml);
        return placemark;
    }

    /**
     * 构造完整kml文件
     * @param name
     * @param placemarkList
     * @return
     */
    public static String getKml(String name,List placemarkList){
        String kml = "\n"
            + "\n"
            + "\t\n"
            + "\t\t"+name+"\n"
            + "\t\t\n"
            + "\t\t\t"+name+"\n"
            + "%s\n"
            + "\t\t\n"
            + "\t\n"
            + "";
        StringBuilder sb = new StringBuilder();
        for(String placemark:placemarkList){
            sb.append(placemark);
        }
        kml = String.format(kml, sb.toString());
        return kml;
    }

}

工具类中内置三种样式，如有其他需要，可自行扩展

使用案例

public void listKml(KmlExportCondition condition,HttpServletResponse response) {
        try{
            String year = systemConfigService.getCurrentYear();
            condition.setYear(year);
            // 获取小班kml数据
            List list = acceptanceMapper.listKml(condition);
            // 组装kml文件
            List placemarkList = new ArrayList<>();
            for(KmlExportBO kmlExportBO:list){
                String placemark = KmlUtil
                    .getPlacemark(kmlExportBO.getName(), kmlExportBO.getKml(), condition.getResult());
                placemarkList.add(placemark);
            }
            String kml = KmlUtil.getKml("小班kml",placemarkList);
            // 文件下载
            OutputStream outputStream = response.getOutputStream();
            response.setContentType("application/vnd.google-earth.kml+xml");
            response.setHeader("Content-Disposition", "attachment;filename=class.kml");
            response.setContentType("application/octet-stream;charset=UTF-8");
            response.addHeader("Pargam", "no-cache");
            response.addHeader("Cache-Control", "no-cache");
            IoUtil.write(outputStream,true,kml.getBytes(Charset.defaultCharset()));
        }catch (Exception e){
            log.error("获取小班kml失败",e);
        }
    }

• 根据条件从数据库中查询矢量数据，并转换为placemark
• 循环遍历矢量数列表，构造完整kml文档
• 将kml文档以文件流的形式供浏览器下载