使用java生成mapbox-gl可读的vector tile

概述

mapbox-gl主要数据源来自mapbox vector tile，本文就是要阐述怎样把postgresql中的地理空间数据转换成vector tile，流程图如下：

配置

该工程采用spring boot+maven，所以第一步少不了pom.xml配置：

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>com.lilei.mvt</groupId>
    <artifactId>vector-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
 
    <name>vector-server</name>
    <url>http://maven.apache.org</url>
 
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.0.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
 
    <repositories>
        <repository>
            <id>ECC</id>
            <url>https://github.com/ElectronicChartCentre/ecc-mvn-repo/raw/master/releases</url>
        </repository>
    </repositories>
 
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-freemarker</artifactId>
        </dependency>
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>2.1.4</version>
        </dependency>
 
        <!-- 数据库 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
 
 
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>42.1.1</version>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
 
        <dependency>
            <groupId>com.vividsolutions</groupId>
            <artifactId>jts</artifactId>
            <version>1.13</version>
        </dependency>
 
        <dependency>
            <groupId>com.google.protobuf</groupId>
            <artifactId>protobuf-java</artifactId>
            <version>2.6.1</version>
        </dependency>
 
        <!-- https://mvnrepository.com/artifact/com.google.protobuf.nano/protobuf-javanano -->
        <dependency>
            <groupId>com.google.protobuf.nano</groupId>
            <artifactId>protobuf-javanano</artifactId>
            <version>3.0.0-alpha-4</version>
        </dependency>
 
 
        <dependency>
            <groupId>no.ecc.vectortile</groupId>
            <artifactId>java-vector-tile</artifactId>
            <version>1.2.1</version>
        </dependency>
 
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
 
 
</project>

添加墨卡托投影转换工具类：

核心内容

解析地理数据，转换成vector tile：

@Override
    public byte[] getContents(String type, int x, int y, int z) {
         
        String sql = null;
         
        if (type.equals("link")){
            sql = "select link_pid,name,st_astext(geom) as geom from beijing_link "
                + "where " + "st_intersects(geom,st_geomfromtext(?,4326)) "
                        + "";
        }else if (type.equals("poi")){
            sql = "select pid,st_astext(geom) as geom from poi5 "
                    + "where " + "st_intersects(geom,st_geomfromtext(?,4326)) "
                            + "";
        }
         
 
        try {
 
            String tile = TileUtils.parseXyz2Bound(x, y, z);
             
            List<Map<String, Object>> results = jdbc.queryForList(sql, tile);
 
            VectorTileEncoder vte = new VectorTileEncoder(4096, 16, false);
 
            for (Map<String, Object> m : results) {
                String wkt = (String) m.get("geom");
 
                Geometry geom = new WKTReader().read(wkt);
                 
                TileUtils.convert2Piexl(x, y, z, geom);
                 
                m.remove("geom");
                 
                vte.addFeature(type, m, geom);
 
            }
             
            return vte.encode();
 
        } catch (ParseException e) {
            e.printStackTrace();
        }
 
        return null;
    }