echart地图数据压缩

引入js工具方法

function convert2EchartsByStr(rawStr,fileName,type){
    var json = JSON.parse(rawStr);
    return convert2Echarts(json,fileName,type);
}

function convert2Echarts(json,fileName,type){
    // Meta tag
    var results="";
    json.UTF8Encoding = true;
    var features = json.features;
    if (!features) {
        return;
    }
    features.forEach(function (feature){
        var encodeOffsets = feature.geometry.encodeOffsets = [];
        var coordinates = feature.geometry.coordinates;
        if (feature.geometry.type === 'Polygon') {
            coordinates.forEach(function (coordinate, idx){
                coordinates[idx] = encodePolygon(
                    coordinate, encodeOffsets[idx] = []
                );
            });
        } else if(feature.geometry.type === 'MultiPolygon') {
            coordinates.forEach(function (polygon, idx1){
                encodeOffsets[idx1] = [];
                polygon.forEach(function (coordinate, idx2) {
                    coordinates[idx1][idx2] = encodePolygon(
                        coordinate, encodeOffsets[idx1][idx2] = []
                    );
                });
            });
        }
    });
    if(type==='json'){
        results=JSON.stringify(json);
    }else{
        results=addEchartsJsWrapper(JSON.stringify(json), fileName);
    }
    return results;
};
function encodePolygon(coordinate, encodeOffsets) {
    var result = '';

    var prevX = quantize(coordinate[0][0]);
    var prevY = quantize(coordinate[0][1]);
    // Store the origin offset
    encodeOffsets[0] = prevX;
    encodeOffsets[1] = prevY;

    for (var i = 0; i < coordinate.length; i++) {
        var point = coordinate[i];
        result+=encode(point[0], prevX);
        result+=encode(point[1], prevY);

        prevX = quantize(point[0]);
        prevY = quantize(point[1]);
    }

    return result;
}

function addAMDWrapper(jsonStr) {
    return ['define(function() {',
        '    return ' + jsonStr + ';',
        '});'].join('\n');
}

function addEchartsJsWrapper(jsonStr,fileName) {
    return ['(function (root, factory) {',
        "   if (typeof define === 'function' && define.amd) {",
        "       define(['exports', 'echarts'], factory);",
        "   } else if (typeof exports === 'object' && typeof exports.nodeName !== 'string') {",
        "       factory(exports, require('echarts'));",
        "   } else {",
        "       factory({}, root.echarts);",
        "   }",
        " }(this, function (exports, echarts) {",
        "       var log = function (msg) {",
        "           if (typeof console !== 'undefined') {",
        "               console && console.error && console.error(msg);",
        "           }",
        "       }",
        " if (!echarts) {",
        "       log('ECharts is not Loaded');",
        "           return;",
        "       }",
        " if (!echarts.registerMap) {",
        "       log('ECharts Map is not loaded')",
        "       return;",
        " }",
        "  echarts.registerMap('"+fileName+"',"+ jsonStr,
        '  )}));'].join('\n');
}

function encode(val, prev){
    // Quantization
    val = quantize(val);
    // var tmp = val;
    // Delta
    val = val - prev;

    if (((val << 1) ^ (val >> 15)) + 64 === 8232) {
        //WTF, 8232 will get syntax error in js code
        val--;
    }
    // ZigZag
    val = (val << 1) ^ (val >> 15);
    // add offset and get unicode
    return String.fromCharCode(val+64);
    // var tmp = {'tmp' : str};
    // try{
    //     eval("(" + JSON.stringify(tmp) + ")");
    // }catch(e) {
    //     console.log(val + 64);
    // }
}

function quantize(val) {
    return Math.ceil(val * 1024);
}

定义工具类

import java.io.FileNotFoundException;
import java.io.FileReader;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

/**
 * echart地图数据格式压缩解压逻辑
 *
 */
public class EchartMapDataConvert {
    //1.得到脚本引擎
    public static final ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");

    static {
        try {
            //2.引擎读取脚本字符串
            engine.eval(new FileReader(EchartMapDataConvert.class.getResource("/echart_map_date_convert.js").getPath()));
        } catch (ScriptException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    // 3.将引擎转换为Invocable，这样才可以掉用js的方法
    public static final Invocable invocable = (Invocable) engine;

    /**
     * 压缩为 echarts 格式的地图
     *
     * @param geoJson 未转义的json字符串
     * @param fileName
     * @param type     json 或 其他（按js处理）
     * @return
     */
    public static String convert2Echarts(String geoJson, String fileName, String type) {
        try {
            //4.使用 invocable.invokeFunction掉用js脚本里的方法，第一個参数为方法名，后面的参数为被调用的js方法的入参
            return (String) invocable.invokeFunction("convert2Echarts", geoJson, fileName, type);
        } catch (ScriptException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * 压缩为 echarts 格式的地图
     *
     * @param geoJson 转义后的json字符串
     * @param fileName
     * @param type     json 或 其他（按js处理）
     * @return
     */
    public static String convert2EchartsByStr(String geoJson, String fileName, String type) {
        try {
            //4.使用 invocable.invokeFunction掉用js脚本里的方法，第一個参数为方法名，后面的参数为被调用的js方法的入参
            return (String) invocable.invokeFunction("convert2EchartsByStr", geoJson, fileName, type);
        } catch (ScriptException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        }
    }
    
}

调用

     public static void main(String[] args) {
         String ret = FileUtil.readFileToString("D:\\wind\\mapjson\\051000000.json", "UTF-8");
         String geometryJSONStr = EchartMapDataConvert.convert2EchartsByStr(ret, "051000000", "json");
         // 将GeometryJSON数据保存到文件
         FileUtil.writeStringToFile(geometryJSONStr, "D:\\wind\\mapjson\\aaaa.json");
    }