339 lines
12 KiB
Markdown
339 lines
12 KiB
Markdown
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---
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title: GeoTools-创建要素Feature
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date: 2023-11-19
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author: ac
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categries:
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- GIS
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tags:
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- GeoTools
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---
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### GeoTools-创建要素
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> csv2shp，通过csv转点shp文件，学习：
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>
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> 1. 如何创建`FeatureType`、`FeatureCollection`和`Features`；
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> 2. 通过`GeometryFactory`构建`Points`点集；
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> 3. 输出shp文件；
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> 4. 设置投影。
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#### 1.数据准备
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下载一份[csv文件](https://docs.geotools.org/latest/userguide/_downloads/d4bcf8751cc3f33a9fb673902a960e53/locations.csv) ，内容格式如下：
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```text
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LAT, LON, CITY, NUMBER
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46.066667, 11.116667, Trento, 140
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44.9441, -93.0852, St Paul, 125
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13.752222, 100.493889, Bangkok, 150
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45.420833, -75.69, Ottawa, 200
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44.9801, -93.251867, Minneapolis, 350
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46.519833, 6.6335, Lausanne, 560
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48.428611, -123.365556, Victoria, 721
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-33.925278, 18.423889, Cape Town, 550
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-33.859972, 151.211111, Sydney, 436
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41.383333, 2.183333, Barcelona, 914
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39.739167, -104.984722, Denver, 869
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52.95, -1.133333, Nottingham, 800
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45.52, -122.681944, Portland, 840
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37.5667,129.681944,Seoul,473
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50.733992,7.099814,Bonn,700,2016
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```
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#### 2.添加依赖
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```xml
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<dependencies>
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<dependency>
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<groupId>org.geotools</groupId>
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<artifactId>gt-shapefile</artifactId>
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<version>${geotools.version}</version>
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</dependency>
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<dependency>
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<groupId>org.geotools</groupId>
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<artifactId>gt-epsg-hsql</artifactId>
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<version>${geotools.version}</version>
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</dependency>
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</dependencies>
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<repositories>
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<repository>
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<id>osgeo</id>
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<name>OSGeo Release Repository</name>
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<url>https://repo.osgeo.org/repository/release/</url>
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<snapshots><enabled>false</enabled></snapshots>
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<releases><enabled>true</enabled></releases>
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</repository>
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<repository>
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<id>osgeo-snapshot</id>
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<name>OSGeo Snapshot Repository</name>
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<url>https://repo.osgeo.org/repository/snapshot/</url>
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<snapshots><enabled>true</enabled></snapshots>
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<releases><enabled>false</enabled></releases>
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</repository>
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</repositories>
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```
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#### 3. 示例
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```java
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package learning;
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import org.geotools.api.feature.simple.SimpleFeature;
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import org.geotools.api.feature.simple.SimpleFeatureType;
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import org.geotools.data.DataUtilities;
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import org.geotools.data.shapefile.ShapefileDataStore;
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import org.geotools.data.shapefile.ShapefileDataStoreFactory;
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import org.geotools.feature.simple.SimpleFeatureBuilder;
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import org.geotools.geometry.jts.JTSFactoryFinder;
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import org.geotools.swing.data.JFileDataStoreChooser;
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import org.locationtech.jts.geom.Coordinate;
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import org.locationtech.jts.geom.GeometryFactory;
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import org.locationtech.jts.geom.Point;
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import javax.swing.*;
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import java.io.BufferedReader;
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import java.io.File;
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import java.io.FileReader;
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import java.io.Serializable;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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/**
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* @author ac
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* @date 2023/11/20 15:44
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*/
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public class Csv2Shape {
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public static void main(String[] args) throws Exception {
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// Set cross-platform look & feel for compatability
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UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
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File file = JFileDataStoreChooser.showOpenFile("csv", null);
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if (file == null) {
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return;
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}
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/*
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* We use the DataUtilities class to create a FeatureType that will describe the data in our
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* shapefile.
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*
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* See also the createFeatureType method below for another, more flexible approach.
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*
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* 通过 DataUtilities 创建 FeatureType ，类似定义shp文件的名称、几何类型、属性字段、空间参考等信息。
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* createType (String typeName, String typeSpec)
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* typeName:要素名称
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* typeSpec：是"name:Type,name2:Type2,..."格式的字符串，用于定义要素的属性字段，其中Type的类型有：
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* Interger（int、Interger）
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* Double（Double, double）
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* String（"",String,string）
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* Geometry（Point,LineString,Polygon,MultiLineString,MultiPolygon,MultiPoint,GeometryCollection）
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* 还可以是 UUID、Date或是Java的类的全名（含包名）
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* 示例：
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* name:"",age:0,geom:Geometry,centroid:Point,url:java.io.URL"
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* id:String,polygonProperty:Polygon:srid=32615
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*/
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final SimpleFeatureType TYPE =
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DataUtilities.createType(
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"Location",
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"the_geom:Point:srid=4326,"
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+ // <- the geometry attribute: Point type
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"name:String,"
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+ // <- a String attribute
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"number:Integer" // a number attribute
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);
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System.out.println("TYPE:" + TYPE);
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/*
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* A list to collect features as we create them.
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*/
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List<SimpleFeature> features = new ArrayList<>();
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/*
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* GeometryFactory will be used to create the geometry attribute of each feature,
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* using a Point object for the location.
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* 创建几何工厂实例，要素构建者实例
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* 通过缓冲流一行行读取，解析数据，构建Point实例
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*/
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GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();
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SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(TYPE);
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try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
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/* First line of the data file is the header */
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String line = reader.readLine();
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System.out.println("Header: " + line);
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for (line = reader.readLine(); line != null; line = reader.readLine()) {
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if (line.trim().length() > 0) { // skip blank lines
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String[] tokens = line.split("\\,");
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double latitude = Double.parseDouble(tokens[0]);
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double longitude = Double.parseDouble(tokens[1]);
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String name = tokens[2].trim();
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int number = Integer.parseInt(tokens[3].trim());
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/* Longitude (= x coord) first ! */
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// 创建几何实例geometry - point
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Point point = geometryFactory.createPoint(new Coordinate(longitude, latitude));
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// 创建要素实例feature
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// feature
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// ↙ ↘
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// geometry properties
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featureBuilder.add(point);
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featureBuilder.add(name);
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featureBuilder.add(number);
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//buildFeature(id)创建一个要素,ID可以是null,当ID为null时会由builder内部生成
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SimpleFeature feature = featureBuilder.buildFeature(null);
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features.add(feature);
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}
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}
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}
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/*
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* Get an output file name and create the new shapefile
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*
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* 设置输出路径
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*/
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File newFile = getNewShapeFile(file);
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// 创建shapefile类型的数据存储工厂实例
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ShapefileDataStoreFactory dataStoreFactory = new ShapefileDataStoreFactory();
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Map<String, Serializable> params = new HashMap<>();
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params.put("url", newFile.toURI().toURL());
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params.put("create spatial index", Boolean.TRUE);
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// 创建一个空的数据存储
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ShapefileDataStore newDataStore = (ShapefileDataStore) dataStoreFactory.createNewDataStore(params);
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/*
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* TYPE is used as a template to describe the file contents
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* 添加类型描述
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*/
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newDataStore.createSchema(TYPE);
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/*
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* Write the features to the shapefile
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* 创建“create”类型的事务，输出shapefile文件
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*/
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Transaction transaction = new DefaultTransaction("create");
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String typeName = newDataStore.getTypeNames()[0];
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SimpleFeatureSource featureSource = newDataStore.getFeatureSource(typeName);
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SimpleFeatureType SHAPE_TYPE = featureSource.getSchema();
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/*
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* The Shapefile format has a couple limitations:
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* - "the_geom" is always first, and used for the geometry attribute name
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* - "the_geom" must be of type Point, MultiPoint, MuiltiLineString, MultiPolygon
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* - Attribute names are limited in length
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* - Not all data types are supported (example Timestamp represented as Date)
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*
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* Each data store has different limitations so check the resulting SimpleFeatureType.
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*/
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System.out.println("SHAPE:" + SHAPE_TYPE);
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if (featureSource instanceof SimpleFeatureStore) {
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SimpleFeatureStore featureStore = (SimpleFeatureStore) featureSource;
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/*
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* SimpleFeatureStore has a method to add features from a
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* SimpleFeatureCollection object, so we use the ListFeatureCollection
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* class to wrap our list of features.
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*/
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SimpleFeatureCollection collection = new ListFeatureCollection(TYPE, features);
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featureStore.setTransaction(transaction);
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try {
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featureStore.addFeatures(collection);
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transaction.commit();
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} catch (Exception problem) {
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problem.printStackTrace();
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transaction.rollback();
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} finally {
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transaction.close();
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}
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System.exit(0); // success!
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} else {
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System.out.println(typeName + " does not support read/write access");
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System.exit(1);
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}
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}
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/**
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* Prompt the user for the name and path to use for the output shapefile
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* 弹窗让用户选择新生成的shp文件的保存位置
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*
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* @param csvFile the input csv file used to create a default shapefile name
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* @return name and path for the shapefile as a new File object
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*/
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private static File getNewShapeFile(File csvFile) {
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String path = csvFile.getAbsolutePath();
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String newPath = path.substring(0, path.length() - 4) + ".shp";
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JFileDataStoreChooser chooser = new JFileDataStoreChooser("shp");
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chooser.setDialogTitle("Save shapefile");
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chooser.setSelectedFile(new File(newPath));
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int returnVal = chooser.showSaveDialog(null);
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if (returnVal != JFileDataStoreChooser.APPROVE_OPTION) {
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// the user cancelled the dialog
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System.exit(0);
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}
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File newFile = chooser.getSelectedFile();
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if (newFile.equals(csvFile)) {
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System.out.println("Error: cannot replace " + csvFile);
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System.exit(0);
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}
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return newFile;
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}
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}
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```
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#### 4. 归纳
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下面是Java中的一些对象与`Geospatial`中的类的对应关系：
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| Java | Geospatial |
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|:-------- |:------------- |
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| `Object` | `Feature` |
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| `Class` | `FeatureType` |
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| `Field` | `Attribute` |
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| `Method` | `Operation` |
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1. 先创建 `SimpleFeatureType`，就像新建了一个`shpefile`文件一样，定义了shp 文件名和属性字段。
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2. 通过缓冲流解析文件中的坐标和属性信息，使用`GeometryFactory`几何工厂实例创建几何实例，再通过`featureBuilder`构建要素实例`feature`
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##### 数据存储
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`DataStore`代表一份要素数据的物理的源，如`shpaefile`文件、数据库（要素会转为SimpleFeature实例对象）。
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##### 要素存储
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`FeatureSource` 提供更易于操作feature data要素数据的API，当使用数据源(如shapefile或数据库表)时，您将首先创建一个`DataStore`对象来连接到物理源，然后检索一个`FeatureSource`来处理要素数据。
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> `FeatureSource`是用来【读取】要素的类似`View`，而其子类`FeatureStore`是用来【读写】要素的类似于`Table`
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```java
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File file = ...
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FileDataStore store = FileDataStoreFinder.getDataStore(file);
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FeatureSource featureSource = store.getFeatureSource();
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```
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##### **事务**
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`Transaction` 是有要素存储`FeatureStore`的事务控制器。
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在这个接口的帮助下，可以安全地修改Shapefiles、数据库等。事务还可以在使用锁定`Feature`要素时提供授权。
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所有操作都被认为是在一个事务中进行的。`Transaction.AUTO_COMMIT`用于表示自动提交事务模式。
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#### 参考文章
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[1] Feature Tutorial https://docs.geotools.org/latest/userguide/tutorial/feature/csv2shp.html
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