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org.h2gis.functions.io.geojson.GeoJsonWriteDriver Maven / Gradle / Ivy
/**
* H2GIS is a library that brings spatial support to the H2 Database Engine
* . H2GIS is developed by CNRS
* cachedColumnNames;
private int columnCountProperties = -1;
/**
* A simple GeoJSON driver to write a spatial table to a GeoJSON file.
*
* @param connection
* @param tableName
* @param fileName
*/
public GeoJsonWriteDriver(Connection connection, String tableName, File fileName) {
this.connection = connection;
this.tableName = tableName;
this.fileName = fileName;
}
/**
* Write the spatial table to GeoJSON format.
*
* @param progress
* @throws SQLException
* @throws java.io.IOException
*/
public void write(ProgressVisitor progress) throws SQLException, IOException {
if (FileUtil.isExtensionWellFormated(fileName, "geojson")) {
writeGeoJson(progress);
} else {
throw new SQLException("Only .geojson extension is supported");
}
}
/**
* Write the spatial table to GeoJSON format.
*
* @param progress
* @throws SQLException
*/
private void writeGeoJson(ProgressVisitor progress) throws SQLException, IOException {
FileOutputStream fos = null;
try {
fos = new FileOutputStream(fileName);
// Read Geometry Index and type
final TableLocation parse = TableLocation.parse(tableName, JDBCUtilities.isH2DataBase(connection.getMetaData()));
List spatialFieldNames = SFSUtilities.getGeometryFields(connection,parse);
if (spatialFieldNames.isEmpty()) {
throw new SQLException(String.format("The table %s does not contain a geometry field", tableName));
}
// Read table content
Statement st = connection.createStatement();
try {
JsonFactory jsonFactory = new JsonFactory();
JsonGenerator jsonGenerator = jsonFactory.createGenerator(new BufferedOutputStream(fos), JsonEncoding.UTF8);
// header of the GeoJSON file
jsonGenerator.writeStartObject();
jsonGenerator.writeStringField("type", "FeatureCollection");
writeCRS(jsonGenerator,SFSUtilities.getAuthorityAndSRID(connection, parse, spatialFieldNames.get(0)));
jsonGenerator.writeArrayFieldStart("features");
ResultSet rs = st.executeQuery(String.format("select * from %s", tableName));
try {
ResultSetMetaData resultSetMetaData = rs.getMetaData();
int geoFieldIndex = JDBCUtilities.getFieldIndex(resultSetMetaData, spatialFieldNames.get(0));
cacheMetadata(resultSetMetaData);
while (rs.next()) {
writeFeature(jsonGenerator, rs, geoFieldIndex);
}
progress.endStep();
// footer
jsonGenerator.writeEndArray();
jsonGenerator.writeEndObject();
jsonGenerator.flush();
jsonGenerator.close();
} finally {
rs.close();
}
} finally {
st.close();
}
} catch (FileNotFoundException ex) {
throw new SQLException(ex);
} finally {
try {
if (fos != null) {
fos.close();
}
} catch (IOException ex) {
throw new SQLException(ex);
}
}
}
/**
* Write a GeoJSON feature.
*
* Features in GeoJSON contain a geometry object and additional properties,
* and a feature collection represents a list of features.
*
* A complete GeoJSON data structure is always an object (in JSON terms). In
* GeoJSON, an object consists of a collection of name/value pairs -- also
* called members. For each member, the name is always a string. Member
* values are either a string, number, object, array or one of the literals:
* true, false, and null. An array consists of elements where each element
* is a value as described above.
*
* Syntax:
*
* { "type": "Feature", "geometry":{"type": "Point", "coordinates": [102.0,
* 0.5]}, "properties": {"prop0": "value0"} }
*
* @param writer
* @param resultSetMetaData
* @param geoFieldIndex
*/
private void writeFeature(JsonGenerator jsonGenerator, ResultSet rs, int geoFieldIndex) throws IOException, SQLException {
// feature header
jsonGenerator.writeStartObject();
jsonGenerator.writeStringField("type", "Feature");
//Write the first geometry
writeGeometry((Geometry) rs.getObject(geoFieldIndex), jsonGenerator);
//Write the properties
writeProperties(jsonGenerator, rs);
// feature footer
jsonGenerator.writeEndObject();
}
/**
* Cache the column name and its index.
*
* @param resultSetMetaData
* @throws SQLException
*/
private void cacheMetadata(ResultSetMetaData resultSetMetaData) throws SQLException {
cachedColumnNames = new LinkedHashMap();
for (int i = 1; i <= resultSetMetaData.getColumnCount(); i++) {
final String fieldTypeName = resultSetMetaData.getColumnTypeName(i);
if (!fieldTypeName.equalsIgnoreCase("geometry")
&& isSupportedPropertyType(resultSetMetaData.getColumnType(i), fieldTypeName)) {
cachedColumnNames.put(resultSetMetaData.getColumnName(i).toUpperCase(), i);
columnCountProperties++;
}
}
}
/**
* Write a JTS geometry to its GeoJSON geometry representation.
*
* Syntax:
*
* "geometry":{"type": "Point", "coordinates": [102.0, 0.5]}
*
* @param jsonGenerator
* @param geometry
*/
private void writeGeometry(Geometry geom, JsonGenerator gen) throws IOException {
gen.writeObjectFieldStart("geometry");
if (geom instanceof Point) {
write((Point) geom, gen);
} else if (geom instanceof MultiPoint) {
write((MultiPoint) geom, gen);
} else if (geom instanceof LineString) {
write((LineString) geom, gen);
} else if (geom instanceof MultiLineString) {
write((MultiLineString) geom, gen);
} else if (geom instanceof Polygon) {
write((Polygon) geom, gen);
} else if (geom instanceof MultiPolygon) {
write((MultiPolygon) geom, gen);
} else if (geom instanceof GeometryCollection) {
write((GeometryCollection) geom, gen);
} else {
throw new RuntimeException("Unsupported Geomery type");
}
gen.writeEndObject();
}
/**
* Point coordinates are in x, y order (easting, northing for projected
* coordinates, longitude, latitude for geographic coordinates):
*
* { "type": "Point", "coordinates": [100.0, 0.0] }
*
*
* @param point
* @param gen
* @throws IOException
*/
private void write(Point point, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "Point");
gen.writeFieldName("coordinates");
writeCoordinate(point.getCoordinate(), gen);
}
/**
* Coordinates of a MultiPoint are an array of positions:
*
* { "type": "MultiPoint", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ] }
*
*
* @param points
* @param gen
* @throws IOException
*/
private void write(MultiPoint points, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "MultiPoint");
gen.writeFieldName("coordinates");
writeCoordinates(points.getCoordinates(), gen);
}
/**
* Coordinates of LineString are an array of positions :
*
* { "type": "LineString", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ] }
*
* @param geom
* @param gen
* @throws IOException
*/
private void write(LineString geom, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "LineString");
gen.writeFieldName("coordinates");
writeCoordinates(geom.getCoordinates(), gen);
}
/**
* Coordinates of a MultiLineString are an array of LineString coordinate
* arrays:
*
* { "type": "MultiLineString", "coordinates": [ [ [100.0, 0.0], [101.0,
* 1.0] ], [ [102.0, 2.0], [103.0, 3.0] ] ] }
*
* @param geom
* @param gen
* @throws IOException
*/
private void write(MultiLineString geom, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "MultiLineString");
gen.writeFieldName("coordinates");
gen.writeStartArray();
for (int i = 0; i < geom.getNumGeometries(); ++i) {
writeCoordinates(geom.getGeometryN(i).getCoordinates(), gen);
}
gen.writeEndArray();
}
/**
* Each element in the geometries array of a GeometryCollection is one of
* the geometry objects described above:
*
* { "type": "GeometryCollection", "geometries": [ { "type": "Point",
* "coordinates": [100.0, 0.0] }, { "type": "LineString", "coordinates": [
* [101.0, 0.0], [102.0, 1.0] ] } ] }
*
* @param coll
* @param gen
* @throws IOException
*/
private void write(GeometryCollection coll, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "GeometryCollection");
gen.writeArrayFieldStart("geometries");
for (int i = 0; i < coll.getNumGeometries(); ++i) {
Geometry geom = coll.getGeometryN(i);
gen.writeStartObject();
if (geom instanceof Point) {
write((Point) geom, gen);
} else if (geom instanceof MultiPoint) {
write((MultiPoint) geom, gen);
} else if (geom instanceof LineString) {
write((LineString) geom, gen);
} else if (geom instanceof MultiLineString) {
write((MultiLineString) geom, gen);
} else if (geom instanceof Polygon) {
write((Polygon) geom, gen);
} else if (geom instanceof MultiPolygon) {
write((MultiPolygon) geom, gen);
} else if (geom instanceof GeometryCollection) {
write((GeometryCollection) geom, gen);
} else {
throw new RuntimeException("Unsupported Geomery type");
}
gen.writeEndObject();
}
gen.writeEndArray();
}
/**
* Coordinates of a Polygon are an array of LinearRing coordinate arrays.
* The first element in the array represents the exterior ring. Any
* subsequent elements represent interior rings (or holes).
*
* No holes:
*
* { "type": "Polygon", "coordinates": [ [ [100.0, 0.0], [101.0, 0.0],
* [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ] ] }
*
* With holes:
*
* { "type": "Polygon", "coordinates": [ [ [100.0, 0.0], [101.0, 0.0],
* [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ], [ [100.2, 0.2], [100.8, 0.2],
* [100.8, 0.8], [100.2, 0.8], [100.2, 0.2] ] ] }
*
* @param geom
* @param gen
* @throws IOException
*/
private void write(Polygon geom, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "Polygon");
gen.writeFieldName("coordinates");
gen.writeStartArray();
writeCoordinates(geom.getExteriorRing().getCoordinates(), gen);
for (int i = 0; i < geom.getNumInteriorRing(); ++i) {
writeCoordinates(geom.getInteriorRingN(i).getCoordinates(), gen);
}
gen.writeEndArray();
}
/**
*
*
* Coordinates of a MultiPolygon are an array of Polygon coordinate arrays:
*
* { "type": "MultiPolygon", "coordinates": [ [[[102.0, 2.0], [103.0, 2.0],
* [103.0, 3.0], [102.0, 3.0], [102.0, 2.0]]], [[[100.0, 0.0], [101.0, 0.0],
* [101.0, 1.0], [100.0, 1.0], [100.0, 0.0]], [[100.2, 0.2], [100.8, 0.2],
* [100.8, 0.8], [100.2, 0.8], [100.2, 0.2]]] ] }
*
* @param geom
* @param gen
* @throws IOException
*/
private void write(MultiPolygon geom, JsonGenerator gen) throws IOException {
gen.writeStringField("type", "MultiPolygon");
gen.writeFieldName("coordinates");
gen.writeStartArray();
for (int i = 0; i < geom.getNumGeometries(); ++i) {
Polygon p = (Polygon) geom.getGeometryN(i);
gen.writeStartArray();
writeCoordinates(p.getExteriorRing().getCoordinates(), gen);
for (int j = 0; j < p.getNumInteriorRing(); ++j) {
writeCoordinates(p.getInteriorRingN(j).getCoordinates(), gen);
}
gen.writeEndArray();
}
gen.writeEndArray();
}
/**
* Write coordinate positions.
*
* @param coordinate
* @param gen
* @throws IOException
*/
private void writeCoordinate(Coordinate coordinate, JsonGenerator gen) throws IOException {
gen.writeStartArray();
gen.writeNumber(coordinate.x);
gen.writeNumber(coordinate.y);
if (!Double.isNaN(coordinate.z)) {
gen.writeNumber(coordinate.z);
}
gen.writeEndArray();
}
/**
* Write coordinate array.
*
* @param coordinates
* @param gen
* @throws IOException
*/
private void writeCoordinates(Coordinate[] coordinates, JsonGenerator gen) throws IOException {
gen.writeStartArray();
for (Coordinate coord : coordinates) {
writeCoordinate(coord, gen);
}
gen.writeEndArray();
}
/**
* Write the GeoJSON properties.
*
* @param jsonGenerator
* @param rs
* @throws IOException
*/
private void writeProperties(JsonGenerator jsonGenerator, ResultSet rs) throws IOException, SQLException {
if (columnCountProperties != -1) {
jsonGenerator.writeObjectFieldStart("properties");
for (Map.Entry entry : cachedColumnNames.entrySet()) {
String string = entry.getKey();
Integer fieldId = entry.getValue();
jsonGenerator.writeObjectField(string, rs.getObject(fieldId));
}
jsonGenerator.writeEndObject();
}
}
/**
* Return true is the SQL type is supported by the GeoJSON driver.
*
* @param sqlTypeId
* @param sqlTypeName
* @return
* @throws SQLException
*/
public boolean isSupportedPropertyType(int sqlTypeId, String sqlTypeName) throws SQLException {
switch (sqlTypeId) {
case Types.BOOLEAN:
case Types.DOUBLE:
case Types.FLOAT:
case Types.INTEGER:
case Types.BIGINT:
case Types.SMALLINT:
case Types.DATE:
case Types.VARCHAR:
case Types.NCHAR:
case Types.CHAR:
return true;
default:
throw new SQLException("Field type not supported by GeoJSON driver: " + sqlTypeName);
}
}
/**
* Write the CRS in the geojson
*
* @param jsonGenerator
* @param authorityAndSRID
* @throws IOException
*/
private void writeCRS(JsonGenerator jsonGenerator, String[] authorityAndSRID) throws IOException {
if (authorityAndSRID[1] != null) {
jsonGenerator.writeObjectFieldStart("crs");
jsonGenerator.writeStringField("type", "name");
jsonGenerator.writeObjectFieldStart("properties");
StringBuilder sb = new StringBuilder("urn:ogc:def:crs:");
sb.append(authorityAndSRID[0]).append("::").append(authorityAndSRID[1]);
jsonGenerator.writeStringField("name", sb.toString());
jsonGenerator.writeEndObject();
jsonGenerator.writeEndObject();
}
}
}
