GeoTools practical guide: teach you step by step to easily realize the visualization of Shapefile vector layer

GeoTools practical guide: teach you step by step to easily realize the visualization of Shapefile vector layer

introduce

This tutorial is designed to guide you through rendering and displaying Shapefile vector layers using the GeoTools library. GeoTools is an open source geographic information system (GIS) toolkit for working with geographic data. Following are the main steps of this tutorial:

1. prepare the environment
2. code analysis
3. sample application
4. custom style

prepare the environment

First, you need to add the GeoTools library to your project. Add dependencies using Maven or Gradle, or simply download the GeoTools jar file and add it to your classpath.

Maven

<properties>
  <geotools.version>29-SNAPSHOT</geotools.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.geotools</groupId>
        <artifactId>gt-shapefile</artifactId>
        <version>${geotools.version}</version>
    </dependency>
    <dependency>
        <groupId>org.geotools</groupId>
        <artifactId>gt-swing</artifactId>
        <version>${geotools.version}</version>
    </dependency>
</dependencies>

Gradle

dependencies {
    implementation "org.geotools:gt-shapefile:${geotoolsVersion}"
    implementation "org.geotools:gt-swing:${geotoolsVersion}"
}

code analysis

In the code example, we created a ShapeFileLabclass called , which reads the Shapefile and displays the rendered layer on the map.

factory class instance

We created two factory class instances, one is StyleFactoryused to create style objects; the other is FilterFactory2used to create filter objects.

    private final StyleFactory sf = CommonFactoryFinder.getStyleFactory();
    private final FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2();

Show Shapefiles

displayShapefile()The method will pop up a wizard window, requiring the user to select the Shapefile to be displayed. This method calls displayLayers()the method after the user selects a file.

private void displayShapefile() {
    
    
        // 创建参数列表，矢量文件（Shapefile）
        List<Parameter<?>> list = new ArrayList<>();
        list.add(
                new Parameter<>(
                        "shape",
                        File.class,
                        "Shapefile文件",
                        "选择需要叠加的Shapefile文件",
                        new KVP(Parameter.EXT, "shp")));
        // 创建一个向导，让用户输入这些参数
        JParameterListWizard wizard =
                new JParameterListWizard("矢量图层叠加展示", "Fill in the following layers", list);
        int finish = wizard.showModalDialog();
        // 如果用户没有完成输入，则退出
        if (finish != JWizard.FINISH) {
    
    
            System.exit(0);
        }
        File shapeFile = (File) wizard.getConnectionParameters().get("shape");
        // 从向导中获取用户输入的文件，并调用displayLayers方法显示图层
        displayLayers(shapeFile);
    }

Load and render Shapefiles

displayLayers()The method first uses FileDataStoreFinderthe loaded Shapefile. Then, create a style for the Shapefile layer and add the layer to MapContentthe object. Finally, use JMapFramethe display map.

    private void displayLayers(File shapeFile) {
    
    
        // 接Shapefile并设置渲染风格
        FileDataStore dataStore = null;
        SimpleFeatureSource shapefileSource = null;
        try {
    
    
            dataStore = FileDataStoreFinder.getDataStore(shapeFile);
            shapefileSource = dataStore.getFeatureSource();
        } catch (IOException e) {
    
    
            throw new RuntimeException(e);
        }

        // 创建一个带有黄线且无填充的基本样式
//        Style shpStyle = SLD.createPolygonStyle(Color.YELLOW, null, 0.0f);
        Style shpStyle = createCustomStyle(sf, ff);
        // 创建JMapFrame并设置菜单、工具栏等
        final MapContent map = new MapContent();
        map.setTitle("图层叠加");

        Layer shpLayer = new FeatureLayer(shapefileSource, shpStyle);
        map.addLayer(shpLayer);

        // C创建一个JMapFrame框架
        frame = new JMapFrame(map);
        frame.setSize(800, 600);
        frame.enableStatusBar(true);
//        frame.enableTool(JMapFrame.Tool.ZOOM, JMapFrame.Tool.PAN, JMapFrame.Tool.RESET);
        frame.enableToolBar(true);
        frame.enableLayerTable(true);

        // 显示地图窗口，当窗口关闭时，应用程序将退出
        frame.setVisible(true);
    }

custom style

In createCustomStyle()the method, we create a custom style that adds a red border to the Shapefile layer. You can modify this method to apply other styles, such as changing the border color, width, or adding padding.

    /**
     * 创建矢量图层样式
     * @param styleFactory 样式工厂
     * @param filterFactory 过滤器工厂
     * @return  矢量图层样式
     */
    public static Style createCustomStyle(StyleFactory styleFactory, FilterFactory2 filterFactory) {
    
    
        // Create a black line for the stroke
        Stroke stroke = styleFactory.createStroke(filterFactory.literal(Color.RED), filterFactory.literal(1));

        // Create a line symbolizer using the stroke
        LineSymbolizer lineSymbolizer = styleFactory.createLineSymbolizer(stroke, null);

        // Create a rule with the line symbolizer
        Rule rule = styleFactory.createRule();
        rule.symbolizers().add(lineSymbolizer);

        // Create a style with the rule
        Style style = styleFactory.createStyle();
        style.featureTypeStyles().add(styleFactory.createFeatureTypeStyle(rule));

        return style;
    }

sample code

import org.geotools.coverage.grid.io.GridCoverage2DReader;
import org.geotools.data.FileDataStore;
import org.geotools.data.FileDataStoreFinder;
import org.geotools.data.Parameter;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.factory.CommonFactoryFinder;
import org.geotools.map.FeatureLayer;
import org.geotools.map.Layer;
import org.geotools.map.MapContent;
import org.geotools.styling.*;
import org.geotools.styling.Stroke;
import org.geotools.swing.JMapFrame;
import org.geotools.swing.data.JParameterListWizard;
import org.geotools.swing.wizard.JWizard;
import org.geotools.util.KVP;
import org.opengis.filter.FilterFactory2;

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

/**
 * 渲染shape文件，并显示在地图上
 */
public class ShapeFileLab {
    
    

    //这行代码创建了一个 StyleFactory 实例，它是 GeoTools 中的一个工厂类，用于创建样式对象。样式对象用于定义地图中地理要素（如点、线、面）的显示方式，包括颜色、线型、填充等。
    private final StyleFactory sf = CommonFactoryFinder.getStyleFactory();
    //这行代码创建了一个 FilterFactory2 实例。FilterFactory2 是 GeoTools 中的一个工厂类，用于创建过滤器对象。过滤器对象用于筛选地理要素，可以基于属性或几何关系来选择特定的地理要素。这个类是 FilterFactory 的一个扩展版本，提供了更多的功能。
    private final FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2();
    //这行代码声明了一个 JMapFrame 类型的私有变量 frame。JMapFrame 是 GeoTools 提供的一个 Swing 组件，用于在窗口中显示地图。通过这个变量，您可以创建一个地图窗口，添加图层、工具栏等组件。
    private JMapFrame frame;
    //这行代码声明了一个 GridCoverage2DReader 类型的私有变量 reader。GridCoverage2DReader 是一个接口，用于读取栅格数据（如 GeoTIFF、NetCDF 等格式）。通过实现这个接口的类（如 GeoTiffReader、NetCDFReader 等），您可以读取和处理栅格数据。
    private GridCoverage2DReader reader;

    public static void main(String[] args) {
    
    
        ShapeFileLab app = new ShapeFileLab();
        app.displayShapefile();
    }

    private void displayShapefile() {
    
    
        // 创建参数列表，矢量文件（Shapefile）
        List<Parameter<?>> list = new ArrayList<>();
        list.add(
                new Parameter<>(
                        "shape",
                        File.class,
                        "Shapefile文件",
                        "选择需要叠加的Shapefile文件",
                        new KVP(Parameter.EXT, "shp")));
        // 创建一个向导，让用户输入这些参数
        JParameterListWizard wizard =
                new JParameterListWizard("矢量图层叠加展示", "Fill in the following layers", list);
        int finish = wizard.showModalDialog();
        // 如果用户没有完成输入，则退出
        if (finish != JWizard.FINISH) {
    
    
            System.exit(0);
        }
        File shapeFile = (File) wizard.getConnectionParameters().get("shape");
        // 从向导中获取用户输入的文件，并调用displayLayers方法显示图层
        displayLayers(shapeFile);
    }

    private void displayLayers(File shapeFile) {
    
    
        // 接Shapefile并设置渲染风格
        FileDataStore dataStore = null;
        SimpleFeatureSource shapefileSource = null;
        try {
    
    
            dataStore = FileDataStoreFinder.getDataStore(shapeFile);
            shapefileSource = dataStore.getFeatureSource();
        } catch (IOException e) {
    
    
            throw new RuntimeException(e);
        }

        // 创建一个带有黄线且无填充的基本样式
//        Style shpStyle = SLD.createPolygonStyle(Color.YELLOW, null, 0.0f);
        Style shpStyle = createCustomStyle(sf, ff);
        // 创建JMapFrame并设置菜单、工具栏等
        final MapContent map = new MapContent();
        map.setTitle("图层叠加");

        Layer shpLayer = new FeatureLayer(shapefileSource, shpStyle);
        map.addLayer(shpLayer);

        // C创建一个JMapFrame框架
        frame = new JMapFrame(map);
        frame.setSize(800, 600);
        frame.enableStatusBar(true);
//        frame.enableTool(JMapFrame.Tool.ZOOM, JMapFrame.Tool.PAN, JMapFrame.Tool.RESET);
        frame.enableToolBar(true);
        frame.enableLayerTable(true);

        // 显示地图窗口，当窗口关闭时，应用程序将退出
        frame.setVisible(true);
    }

    /**
     * 创建矢量图层样式
     * @param styleFactory 样式工厂
     * @param filterFactory 过滤器工厂
     * @return  矢量图层样式
     */
    public static Style createCustomStyle(StyleFactory styleFactory, FilterFactory2 filterFactory) {
    
    
        // Create a black line for the stroke
        Stroke stroke = styleFactory.createStroke(filterFactory.literal(Color.RED), filterFactory.literal(1));

        // Create a line symbolizer using the stroke
        LineSymbolizer lineSymbolizer = styleFactory.createLineSymbolizer(stroke, null);

        // Create a rule with the line symbolizer
        Rule rule = styleFactory.createRule();
        rule.symbolizers().add(lineSymbolizer);

        // Create a style with the rule
        Style style = styleFactory.createStyle();
        style.featureTypeStyles().add(styleFactory.createFeatureTypeStyle(rule));

        return style;
    }
}

sample application

To run the sample application, copy the code into a ShapeFileLab.javafile named . Then, compile and run the file. You should be able to see a map window with the Shapefile layer you selected.