geotools源码解析——postgis篇

1. geotools简介

geotools是java语言封装的空间数据框架。类似于spring之与java web项目，geotools提供丰富的GIS组件，可用于快速二次搭建GIS平台。详细可登录geotools官网了解其功能信息（https://geotools.org/）。

2. geotools postgis源码解析

postgis是postgresql数据库的扩展，可以理解为postgresql的GIS化功能封装。

本博文用postgresql 11和postgis 3.1.1版本给大家演示

2.1. 用geotools连接postgis

数据源获取，其原理于JDBC数据库连接，在geotools中可称为初始化数据存储（geoserver借鉴于geotools概念）。可参考类DataStore，JDBCDataSotre。

package com.geodatastore.postgis;

import org.geotools.data.*;
import org.geotools.data.collection.ListFeatureCollection;
import org.geotools.data.postgis.PostgisNGDataStoreFactory;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.data.simple.SimpleFeatureIterator;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.data.simple.SimpleFeatureStore;
import org.geotools.feature.simple.SimpleFeatureBuilder;
import org.geotools.feature.simple.SimpleFeatureTypeImpl;
import org.geotools.filter.text.cql2.CQL;
import org.geotools.filter.text.cql2.CQLException;
import org.geotools.geometry.jts.ReferencedEnvelope;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.Point;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.feature.type.Name;
import org.opengis.filter.Filter;
import org.opengis.filter.identity.FeatureId;

import java.awt.*;
import java.io.IOException;
import java.util.*;
import java.util.List;

public class PostgisDataStore {

    private DataStore dataStore = null;
    private GeometryFactory geometryFactory = null;
    private final String tableName = "pois";
    //获取类型
    private SimpleFeatureType type = null;
    public PostgisDataStore() {
        this.geometryFactory = new GeometryFactory();
    };

    public  DataStore getDataStore(Map map) throws IOException {
        Map params = new HashMap<>();
        params.put(PostgisNGDataStoreFactory.DBTYPE.key, "postgis");
        params.put(PostgisNGDataStoreFactory.HOST.key, map.get("host"));
        params.put(PostgisNGDataStoreFactory.PORT.key, 5432);
        params.put(PostgisNGDataStoreFactory.SCHEMA.key, map.get("schema"));
        params.put(PostgisNGDataStoreFactory.DATABASE.key, map.get("database"));
        params.put(PostgisNGDataStoreFactory.USER.key, map.get("user"));
        params.put(PostgisNGDataStoreFactory.PASSWD.key, map.get("passwd"));

        dataStore = DataStoreFinder.getDataStore(params);

        if (dataStore == null) {
            throw new IOException("数据库连接未成功");
        } else {
            System.out.println("数据库连接成功");
        }
        return dataStore;
    }
}

2.2. 创建矢量要素Feature

本文使用单一简单要素SimpleFeature给大家讲解，暂不解析复杂多点线面要素源码。以单点Point为例给大家解析，参考类Point，SimpleFeature，Geometry

public SimpleFeature createSimplePointFeatureByLonLat(Double lon,Double lat) throws IOException {
        SimpleFeatureSource simpleFeatureSource = null;

        Point point = null;
        //构建要素
        SimpleFeature feature = null;
        if (dataStore != null) {
            simpleFeatureSource = dataStore.getFeatureSource(tableName);
            type = simpleFeatureSource.getSchema();
            SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(type);
            point = geometryFactory.createPoint(new Coordinate(lon,lat));
            //属性值顺序与SimpleFeatureType对应
            List