第07章 - GeoJSON 与 TWKB 数据交换

public class GeoJsonWriter {
  public static final String EPSG_PREFIX = "EPSG:";

  public GeoJsonWriter();          // 等价于 GeoJsonWriter(8)
  public GeoJsonWriter(int decimals);

  public void setEncodeCRS(boolean isEncodeCRS);
  public void setForceCCW(boolean isForceCCW);

  public String write(Geometry geometry);
  public void write(Geometry geometry, Writer writer) throws IOException;
}

private double scale;
private boolean isEncodeCRS = true;    // 默认 true！
private boolean isForceCCW = false;

import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.io.WKTReader;
import org.locationtech.jts.io.geojson.GeoJsonWriter;

GeometryFactory gf = new GeometryFactory();
Geometry poly = new WKTReader(gf).read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");

System.out.println(new GeoJsonWriter().write(poly));

GeoJsonWriter writer = new GeoJsonWriter();
writer.setEncodeCRS(false);      // 关键一行
String json = writer.write(geom);

GeometryFactory gf = new GeometryFactory();
WKTReader reader = new WKTReader(gf);
Geometry pt = reader.read("POINT (116.39742800001 39.90923000002)");

for (int d : new int[] {8, 6, 3}) {
  GeoJsonWriter w = new GeoJsonWriter(d);
  w.setEncodeCRS(false);
  System.out.println("decimals=" + d + " -> " + w.write(pt));
}

GeometryFactory gf = new GeometryFactory();
WKTReader reader = new WKTReader(gf);

// 故意写一个顺时针的矩形（外环）
Geometry cw = reader.read("POLYGON ((0 0, 0 10, 10 10, 10 0, 0 0))");

GeoJsonWriter plain = new GeoJsonWriter();
plain.setEncodeCRS(false);
System.out.println("不强制: " + plain.write(cw));

GeoJsonWriter ccw = new GeoJsonWriter();
ccw.setEncodeCRS(false);
ccw.setForceCCW(true);
System.out.println("强制CCW: " + ccw.write(cw));

GeometryFactory gf = new GeometryFactory();
WKTReader reader = new WKTReader(gf);
GeoJsonWriter writer = new GeoJsonWriter();
writer.setEncodeCRS(false);

for (String wkt : new String[] {
    "POINT EMPTY", "LINESTRING EMPTY", "POLYGON EMPTY", "GEOMETRYCOLLECTION EMPTY"}) {
  System.out.println(wkt + " -> " + writer.write(reader.read(wkt)));
}

public class GeoJsonReader {
  public GeoJsonReader();
  public GeoJsonReader(GeometryFactory geometryFactory);
  public Geometry read(String json) throws ParseException;
  public Geometry read(Reader reader) throws ParseException;
}

import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.io.ParseException;
import org.locationtech.jts.io.geojson.GeoJsonReader;

public class ReadKinds {

  public static void main(String[] args) throws ParseException {
    GeoJsonReader reader = new GeoJsonReader();

    // 1. 纯几何
    Geometry g1 = reader.read(
        "{\"type\":\"Point\",\"coordinates\":[1,2]}");
    System.out.println("几何   = " + g1);

    // 2. Feature（属性被丢弃，只取 geometry）
    Geometry g2 = reader.read(
        "{\"type\":\"Feature\",\"geometry\":{\"type\":\"Point\",\"coordinates\":[1,2]},"
        + "\"properties\":{\"name\":\"A\"}}");
    System.out.println("Feature= " + g2);

    // 3. FeatureCollection（读成 GeometryCollection）
    Geometry g3 = reader.read(
        "{\"type\":\"FeatureCollection\",\"features\":["
        + "{\"type\":\"Feature\",\"geometry\":{\"type\":\"Point\",\"coordinates\":[1,2]},\"properties\":{}},"
        + "{\"type\":\"Feature\",\"geometry\":{\"type\":\"Point\",\"coordinates\":[3,4]},\"properties\":{}}]}");
    System.out.println("FC     = " + g3 + " 元素数=" + g3.getNumGeometries());
  }
}

import org.locationtech.jts.io.ParseException;
import org.locationtech.jts.io.geojson.GeoJsonReader;

public class BadGeoJson {

  public static void main(String[] args) {
    GeoJsonReader reader = new GeoJsonReader();
    String[] bad = {
        "{\"type\":\"Circle\",\"coordinates\":[1,2]}",           // 未知类型
        "{\"coordinates\":[1,2]}",                                  // 缺 type
        "{not json}",                                               // 非法 JSON
        "{\"type\":\"Point\",\"coordinates\":[\"a\",\"b\"]}" // 非数字
    };
    for (String json : bad) {
      try {
        System.out.println("意外成功: " + reader.read(json));
      } catch (ParseException e) {
        System.out.println("ParseException: " + e.getMessage());
      } catch (RuntimeException e) {
        System.out.println("RuntimeException(" + e.getClass().getSimpleName()
            + "): " + e.getMessage());
      }
    }
  }
}

public Geometry strictParse(String json) throws ParseException {
  Geometry g = new GeoJsonReader().read(json);
  if (g.isEmpty()) return g;

  // 1. 坐标必须在合理范围内（WGS84 经纬度）
  org.locationtech.jts.geom.Envelope env = g.getEnvelopeInternal();
  if (env.getMinX() < -180 || env.getMaxX() > 180
      || env.getMinY() < -90 || env.getMaxY() > 90) {
    throw new IllegalArgumentException("coordinate out of WGS84 range: " + env);
  }
  // 2. 面几何必须有效
  if (g.getDimension() == 2 && !g.isValid()) {
    throw new IllegalArgumentException("invalid polygon: " + g);
  }
  return g;
}

// 带 crs 的 GeoJSON
String withCrs = "{\"type\":\"Point\",\"coordinates\":[1,2],"
    + "\"crs\":{\"type\":\"name\",\"properties\":{\"name\":\"EPSG:4326\"}}}";

System.out.println("默认构造器 SRID = "
    + new GeoJsonReader().read(withCrs).getSRID());

GeometryFactory gf4326 = new GeometryFactory(new PrecisionModel(), 4326);
System.out.println("指定工厂 SRID   = "
    + new GeoJsonReader(gf4326).read("{\"type\":\"Point\",\"coordinates\":[1,2]}").getSRID());

GeoJsonReader reader = new GeoJsonReader();
Geometry p = reader.read("{\"type\":\"Point\",\"coordinates\":[1,2,3]}");

System.out.println("toString = " + p);
System.out.println("维度     = "
    + ((Point) p).getCoordinateSequence().getDimension());
System.out.println("显式输出 = " + new WKTWriter(3).write(p));

GeoJsonWriter w = new GeoJsonWriter();
w.setEncodeCRS(false);
System.out.println(w.write(new WKTReader().read("POINT Z (1 2 3)")));

WKTReader r = new WKTReader(new GeometryFactory());
GeoJsonWriter w = new GeoJsonWriter();
w.setEncodeCRS(false);

// 1. 带 M 的几何写出去
Geometry m = r.read("POINT M (1 2 4)");
String json = w.write(m);
System.out.println("写出 = " + json);

// 2. 读回来看看变成什么
Geometry back = new GeoJsonReader().read(json);
System.out.println("读回 = " + new WKTWriter(3).write(back));

// 第 1 字节：几何类型（低 4 位）+ XY 精度（高位，ZigZag 编码后左移 4 位）
final int geometryType = header.geometryType().getValue();
final int precisionHeader = Varint.zigZagEncode(header.xyPrecision()) << 4;
typeAndPrecisionHeader = precisionHeader | geometryType;
out.writeByte(typeAndPrecisionHeader);

// 第 2 字节：元数据标志位
metadataHeader = (hasBBOX  ? 0b00000001 : 0)
               | (hasSize  ? 0b00000010 : 0)
               | (hasIdList? 0b00000100 : 0)
               | (hasExtPrecision ? 0b00001000 : 0)
               | (isEmpty   ? 0b00010000 : 0);
out.writeByte(metadataHeader);

// 第 3 字节（仅当有 Z/M 时）：扩展维度
if (header.hasExtendedPrecision()) {
  int extendedDimsHeader = (hasZ ? 0b00000001 : 0) | (hasM ? 0b00000010 : 0);
  extendedDimsHeader |= zPrecision << 2;
  extendedDimsHeader |= mPrecision << 5;
  out.writeByte(extendedDimsHeader);
}

// 可选：几何体长度（varint）
if (header.hasSize()) {
  writeUnsignedVarInt(header.geometryBodySize(), out);
}

import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.io.WKBWriter;
import org.locationtech.jts.io.WKTReader;
import org.locationtech.jts.io.twkb.TWKBReader;
import org.locationtech.jts.io.twkb.TWKBWriter;

GeometryFactory gf = new GeometryFactory();
Geometry poly = new WKTReader(gf).read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");

byte[] twkb = new TWKBWriter().write(poly);
System.out.println("长度 = " + twkb.length);
System.out.println("十六进制 = " + WKBWriter.toHex(twkb));
System.out.println("读回 = " + new TWKBReader().read(twkb));

Geometry poly = new WKTReader(new GeometryFactory())
    .read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");
System.out.println(((Polygon) poly).getExteriorRing()
    .getCoordinateSequence().hasZ());   // true

import java.util.ArrayList;
import java.util.List;

import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LineString;
import org.locationtech.jts.io.WKBWriter;
import org.locationtech.jts.io.twkb.TWKBReader;
import org.locationtech.jts.io.twkb.TWKBWriter;

public class PrecisionImpact {

  public static void main(String[] args) throws Exception {
    GeometryFactory gf = new GeometryFactory();
    Coordinate[] pts = new Coordinate[1000];
    for (int i = 0; i < pts.length; i++) {
      pts[i] = new Coordinate(116.397428 + i * 1e-5, 39.90923 + i * 1e-5);
    }
    Geometry line = gf.createLineString(pts);

    int wkbLen = new WKBWriter().write(line).length;
    System.out.printf("WKB: %d 字节, %d 点%n", wkbLen, line.getNumPoints());

    for (int p : new int[] {7, 6, 5, 4}) {
      TWKBWriter w = new TWKBWriter();
      w.setXYPrecision(p);
      byte[] b = w.write(line);
      LineString rt = (LineString) new TWKBReader().read(b);
      System.out.printf("precision=%d: %5d 字节 (%5.1f%%), 读回 %d 点, 首点 %s%n",
          p, b.length, b.length * 100.0 / wkbLen, rt.getNumPoints(), rt.getCoordinateN(0));
    }
  }
}

TWKBWriter base = new TWKBWriter();
TWKBWriter withBbox = new TWKBWriter();
withBbox.setIncludeBbox(true);
TWKBWriter withSize = new TWKBWriter();
withSize.setIncludeSize(true);

Geometry poly = new WKTReader().read("POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))");
System.out.println("默认      = " + base.write(poly).length + " 字节");
System.out.println("带 bbox   = " + withBbox.write(poly).length + " 字节");
System.out.println("带 size   = " + withSize.write(poly).length + " 字节");

GeometryFactory gf = new GeometryFactory();

// 情况 1：几何自带 Z，即使不调 setEncodeZ，也会编码 Z
Geometry gz = gf.createPoint(new Coordinate(1, 2, 3.456));
byte[] b1 = new TWKBWriter().write(gz);
System.out.println("Z几何不设开关 -> "
    + new WKTWriter(3).write(new TWKBReader().read(b1)));

// 情况 2：几何只有 XY，调了 setEncodeZ(true) 也只是写个 0
Geometry gxy = gf.createPoint(new Coordinate(1, 2));
TWKBWriter w = new TWKBWriter();
w.setEncodeZ(true);
byte[] b2 = w.write(gxy);
System.out.println("XY几何设Z开关 -> "
    + new WKTWriter(3).write(new TWKBReader().read(b2)));

private static TWKBHeader setDimensions(Geometry g, TWKBHeader header) {
    if (g.isEmpty()) {
        return header.setHasZ(false).setHasM(false);
    }
    if (g instanceof Point) {
        return setDimensions(((Point) g).getCoordinateSequence(), header);
    }
    // ... LineString / Polygon 类似
}

private static TWKBHeader setDimensions(CoordinateSequence seq, TWKBHeader header) {
    boolean hasZ = seq.hasZ();
    boolean hasM = seq.hasM();
    return header.setHasZ(hasZ).setHasM(hasM);
}

Geometry g = new GeometryFactory().createPoint(new Coordinate(1, 2));
g.setSRID(4326);
byte[] b = new TWKBWriter().write(g);
System.out.println("读回 SRID = " + new TWKBReader().read(b).getSRID());

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;

import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.io.ParseException;
import org.locationtech.jts.io.WKBReader;
import org.locationtech.jts.io.WKBWriter;

/**
 * 自定义帧格式：magic(2) + version(1) + srid(4) + geomLen(4) + geom(WKB) + attrLen(2) + attr(UTF-8)
 */
public class MyGeoFrame {

  private static final short MAGIC = (short) 0x4A54;   // "JT"
  private static final byte VERSION = 1;

  public static byte[] encode(Geometry geom, String attr) throws IOException {
    byte[] wkb = new WKBWriter(2, true).write(geom);
    byte[] attrBytes = attr == null
        ? new byte[0]
        : attr.getBytes(StandardCharsets.UTF_8);

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    DataOutputStream out = new DataOutputStream(baos);
    out.writeShort(MAGIC);
    out.writeByte(VERSION);
    out.writeInt(geom.getSRID());
    out.writeInt(wkb.length);
    out.write(wkb);
    out.writeShort(attrBytes.length);
    out.write(attrBytes);
    out.flush();
    return baos.toByteArray();
  }

  public static Geometry decodeGeometry(byte[] frame) throws IOException, ParseException {
    java.io.DataInputStream in = new java.io.DataInputStream(
        new java.io.ByteArrayInputStream(frame));
    short magic = in.readShort();
    if (magic != MAGIC) {
      throw new IOException("bad magic: " + Integer.toHexString(magic));
    }
    byte version = in.readByte();
    if (version != VERSION) {
      throw new IOException("unsupported version: " + version);
    }
    in.readInt();                            // srid（WKB 里已带，这里冗余存放便于快速读取）
    int geomLen = in.readInt();
    byte[] wkb = new byte[geomLen];
    in.readFully(wkb);
    return new WKBReader().read(wkb);
  }
}