Class WKBWriter
Geometry
into Well-Known Binary format.
Supports use of an OutStream
, which allows easy use
with arbitrary byte stream sinks.
The WKB format is specified in the OGC Simple Features for SQL specification. This implementation also supports the Extended WKB standard. Extended WKB allows writing 3-dimensional coordinates and including the geometry SRID value. The presence of 3D coordinates is signified by setting the high bit of the wkbType word. The presence of an SRID is signified by setting the third bit of the wkbType word. EWKB format is upward compatible with the original SFS WKB format.
Empty Points cannot be represented in WKB; an
IllegalArgumentException
will be thrown if one is
written.
The WKB specification does not support representing LinearRing
s;
they will be written as LineString
s.
This class is designed to support reuse of a single instance to read multiple geometries. This class is not thread-safe; each thread should create its own instance.
Syntax
The following syntax specification describes the version of Well-Known Binary supported by JTS.The specification uses a syntax language similar to that used in the C language. Bitfields are specified from hi-order to lo-order bits.
byte = 1 byte uint32 = 32 bit unsigned integer (4 bytes) double = double precision number (8 bytes) abstract Point { } Point2D extends Point { double x; double y; } Point3D extends Point { double x; double y; double z; } LinearRing { uint32 numPoints; Point points[numPoints]; } enum wkbGeometryType { wkbPoint = 1, wkbLineString = 2, wkbPolygon = 3, wkbMultiPoint = 4, wkbMultiLineString = 5, wkbMultiPolygon = 6, wkbGeometryCollection = 7 } enum byteOrder { wkbXDR = 0, // Big Endian wkbNDR = 1 // Little Endian } WKBType { uint32 wkbGeometryType : 8; // values from enum wkbGeometryType } EWKBType { uint32 is3D : 1; // 0 = 2D, 1 = 3D uint32 noData1 : 1; uint32 hasSRID : 1; // 0, no, 1 = yes uint32 noData2 : 21; uint32 wkbGeometryType : 8; // values from enum wkbGeometryType } abstract WKBGeometry { byte byteOrder; // values from enum byteOrder EWKBType wkbType [ uint32 srid; ] // only if hasSRID = yes } WKBPoint extends WKBGeometry { Point point; } WKBLineString extends WKBGeometry { uint32 numCoords; Point points[numCoords]; } WKBPolygon extends WKBGeometry { uint32 numRings; LinearRing rings[numRings]; } WKBMultiPoint extends WKBGeometry { uint32 numElems; WKBPoint elems[numElems]; } WKBMultiLineString extends WKBGeometry { uint32 numElems; WKBLineString elems[numElems]; } wkbMultiPolygon extends WKBGeometry { uint32 numElems; WKBPolygon elems[numElems]; } WKBGeometryCollection extends WKBGeometry { uint32 numElems; WKBGeometry elems[numElems]; }
- See Also:
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate byte[]
private ByteArrayOutputStream
private OutStream
private int
private boolean
private int
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Constructor Summary
ConstructorsConstructorDescriptionCreates a writer that writesGeometry
s with output dimension = 2 and BIG_ENDIAN byte orderWKBWriter
(int outputDimension) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates andByteOrderValues.BIG_ENDIAN
byte order.WKBWriter
(int outputDimension, boolean includeSRID) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates andByteOrderValues.BIG_ENDIAN
byte order.WKBWriter
(int outputDimension, int byteOrder) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates and byte order If the input geometry has a small coordinate dimension, coordinates will be padded withCoordinate.NULL_ORDINATE
.WKBWriter
(int outputDimension, int byteOrder, boolean includeSRID) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates and byte order. -
Method Summary
Modifier and TypeMethodDescriptionstatic String
bytesToHex
(byte[] bytes) Deprecated.static String
toHex
(byte[] bytes) Converts a byte array to a hexadecimal string.private static char
toHexDigit
(int n) byte[]
Writes aGeometry
into a byte array.void
private void
private void
writeCoordinate
(CoordinateSequence seq, int index, OutStream os) private void
writeCoordinateSequence
(CoordinateSequence seq, boolean writeSize, OutStream os) private void
writeGeometryCollection
(int geometryType, GeometryCollection gc, OutStream os) private void
writeGeometryType
(int geometryType, Geometry g, OutStream os) private void
private void
writeLineString
(LineString line, OutStream os) private void
writePoint
(Point pt, OutStream os) private void
writePolygon
(Polygon poly, OutStream os)
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Field Details
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outputDimension
private int outputDimension -
byteOrder
private int byteOrder -
includeSRID
private boolean includeSRID -
byteArrayOS
-
byteArrayOutStream
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buf
private byte[] buf
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Constructor Details
-
WKBWriter
public WKBWriter()Creates a writer that writesGeometry
s with output dimension = 2 and BIG_ENDIAN byte order -
WKBWriter
public WKBWriter(int outputDimension) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates andByteOrderValues.BIG_ENDIAN
byte order. If the input geometry has a small coordinate dimension, coordinates will be padded withCoordinate.NULL_ORDINATE
.- Parameters:
outputDimension
- the coordinate dimension to output (2 or 3)
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WKBWriter
public WKBWriter(int outputDimension, boolean includeSRID) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates andByteOrderValues.BIG_ENDIAN
byte order. This constructor also takes a flag to control whether srid information will be written. If the input geometry has a smaller coordinate dimension, coordinates will be padded withCoordinate.NULL_ORDINATE
.- Parameters:
outputDimension
- the coordinate dimension to output (2 or 3)includeSRID
- indicates whether SRID should be written
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WKBWriter
public WKBWriter(int outputDimension, int byteOrder) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates and byte order If the input geometry has a small coordinate dimension, coordinates will be padded withCoordinate.NULL_ORDINATE
.- Parameters:
outputDimension
- the coordinate dimension to output (2 or 3)byteOrder
- the byte ordering to use
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WKBWriter
public WKBWriter(int outputDimension, int byteOrder, boolean includeSRID) Creates a writer that writesGeometry
s with the given dimension (2 or 3) for output coordinates and byte order. This constructor also takes a flag to control whether srid information will be written. If the input geometry has a small coordinate dimension, coordinates will be padded withCoordinate.NULL_ORDINATE
.- Parameters:
outputDimension
- the coordinate dimension to output (2 or 3)byteOrder
- the byte ordering to useincludeSRID
- indicates whether SRID should be written
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Method Details
-
bytesToHex
Deprecated.Converts a byte array to a hexadecimal string.- Parameters:
bytes
-- Returns:
- a string of hexadecimal digits
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toHex
Converts a byte array to a hexadecimal string.- Parameters:
bytes
- a byte array- Returns:
- a string of hexadecimal digits
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toHexDigit
private static char toHexDigit(int n) -
write
Writes aGeometry
into a byte array.- Parameters:
geom
- the geometry to write- Returns:
- the byte array containing the WKB
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write
- Parameters:
geom
- the geometry to writeos
- the out stream to write to- Throws:
IOException
- if an I/O error occurs
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writePoint
- Throws:
IOException
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writeLineString
- Throws:
IOException
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writePolygon
- Throws:
IOException
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writeGeometryCollection
private void writeGeometryCollection(int geometryType, GeometryCollection gc, OutStream os) throws IOException - Throws:
IOException
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writeByteOrder
- Throws:
IOException
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writeGeometryType
- Throws:
IOException
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writeInt
- Throws:
IOException
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writeCoordinateSequence
private void writeCoordinateSequence(CoordinateSequence seq, boolean writeSize, OutStream os) throws IOException - Throws:
IOException
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writeCoordinate
- Throws:
IOException
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