org.geotools.data.shapefile.shp

Class ShapefileReader

Object

ShapefileReader

All Implemented Interfaces:

FileReader

public class ShapefileReader
extends Object
implements FileReader

The general use of this class is:

 FileChannel in = new FileInputStream("thefile.dbf").getChannel();
 ShapefileReader r = new ShapefileReader( in ) while (r.hasNext()) { Geometry
 shape = (Geometry) r.nextRecord().shape() // do stuff } r.close();

 

You don't have to immediately ask for the shape from the record. The record will contain the bounds of the shape and will only read the shape when the shape() method is called. This ShapefileReader.Record is the same object every time, so if you need data from the Record, be sure to copy it.

Author:

jamesm, aaime, Ian Schneider

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	ShapefileReader.Record The reader returns only one Record instance in its lifetime.

Constructor Summary

Constructors

Constructor and Description
ShapefileReader(ShpFiles shapefileFiles, boolean strict, boolean useMemoryMapped, GeometryFactory gf) Creates a new instance of ShapeFile.
ShapefileReader(ShpFiles shapefileFiles, boolean strict, boolean useMemoryMapped, GeometryFactory gf, boolean onlyRandomAccess) Creates a new instance of ShapeFile.

Method Summary

Modifier and Type	Method and Description
void	close() Clean up any resources.
void	disableShxUsage() Disables .shx file usage.
static int	fill(ByteBuffer buffer, ReadableByteChannel channel)
int	getCount(int count) Parses the shpfile counting the records.
ShapefileHeader	getHeader() Get the header.
void	goTo(int offset) Moves the reader to the specified byte offset in the file.
boolean	hasNext() If there exists another record.
String	id() An id for the reader.
ShapefileReader.Record	nextRecord() Fetch the next record information.
ShapefileReader.Record	recordAt(int offset) Sets the current location of the byteStream to offset and returns the next record.
void	setFlatGeometry(boolean flatGeometry)
void	setHandler(ShapeHandler handler)
Object	shapeAt(int offset) Returns the shape at the specified byte distance from the beginning of the file.
boolean	supportsRandomAccess()
int	transferTo(ShapefileWriter writer, int recordNum, double[] bounds) Transfer (by bytes) the data at the current record to the ShapefileWriter.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ShapefileReader

public ShapefileReader(ShpFiles shapefileFiles,
                       boolean strict,
                       boolean useMemoryMapped,
                       GeometryFactory gf)
                throws IOException,
                       ShapefileException

Creates a new instance of ShapeFile.

Parameters:

shapefileFiles - The ReadableByteChannel this reader will use.

strict - True to make the header parsing throw Exceptions if the version or magic number are incorrect.

Throws:

IOException - If problems arise.

ShapefileException - If for some reason the file contains invalid records.

ShapefileReader

public ShapefileReader(ShpFiles shapefileFiles,
                       boolean strict,
                       boolean useMemoryMapped,
                       GeometryFactory gf,
                       boolean onlyRandomAccess)
                throws IOException,
                       ShapefileException

Creates a new instance of ShapeFile.

Parameters:

shapefileFiles - The ReadableByteChannel this reader will use.

strict - True to make the header parsing throw Exceptions if the version or magic number are incorrect.

useMemoryMapped - Wheter to enable memory mapping or not

gf - The geometry factory used to build the geometries

onlyRandomAccess - When true sets up the reader to do exclusively read driven by goTo(x) and thus avoids opening the .shx file

Throws:

IOException - If problems arise.

ShapefileException - If for some reason the file contains invalid records.

Method Detail

disableShxUsage

public void disableShxUsage()
                     throws IOException

Disables .shx file usage. By doing so you drop support for sparse shapefiles, the .shp will have to be without holes, all the valid shapefile records will have to be contiguous.

Throws:

IOException

fill

public static int fill(ByteBuffer buffer,
                       ReadableByteChannel channel)
                throws IOException

Throws:

IOException

getHeader

public ShapefileHeader getHeader()

Get the header. Its parsed in the constructor.

Returns:

The header that is associated with this file.

close

public void close()
           throws IOException

Clean up any resources. Closes the channel.

Throws:

IOException - If errors occur while closing the channel.

supportsRandomAccess

public boolean supportsRandomAccess()

hasNext

public boolean hasNext()
                throws IOException

If there exists another record. Currently checks the stream for the presence of 8 more bytes, the length of a record. If this is true and the record indicates the next logical record number, there exists more records.

Returns:

True if has next record, false otherwise.

Throws:

IOException

transferTo

public int transferTo(ShapefileWriter writer,
                      int recordNum,
                      double[] bounds)
               throws IOException

Transfer (by bytes) the data at the current record to the ShapefileWriter.

Parameters:

bounds - double array of length four for transfering the bounds into

Returns:

The length of the record transfered in bytes

Throws:

IOException

nextRecord

public ShapefileReader.Record nextRecord()
                                  throws IOException

Fetch the next record information.

Returns:

The record instance associated with this reader.

Throws:

IOException

goTo

public void goTo(int offset)
          throws IOException,
                 UnsupportedOperationException

Moves the reader to the specified byte offset in the file. Mind that:

• it's your responsibility to ensure the offset corresponds to the actual beginning of a shape struct
• once you call this, reading with hasNext/next on sparse shapefiles will be broken (we don't know anymore at which shape we are)

Parameters:

offset -

Throws:

IOException

UnsupportedOperationException

shapeAt

public Object shapeAt(int offset)
               throws IOException,
                      UnsupportedOperationException

Returns the shape at the specified byte distance from the beginning of the file. Mind that:

• it's your responsibility to ensure the offset corresponds to the actual beginning of a shape struct
• once you call this, reading with hasNext/next on sparse shapefiles will be broken (we don't know anymore at which shape we are)

Parameters:

offset -

Throws:

IOException

UnsupportedOperationException

recordAt

public ShapefileReader.Record recordAt(int offset)
                                throws IOException,
                                       UnsupportedOperationException

Sets the current location of the byteStream to offset and returns the next record. Usually used in conjuctions with the shx file or some other index file. Mind that:

• it's your responsibility to ensure the offset corresponds to the actual beginning of a shape struct
• once you call this, reading with hasNext/next on sparse shapefiles will be broken (we don't know anymore at which shape we are)

Parameters:

offset - If using an shx file the offset would be: 2 * (index.getOffset(i))

Returns:

The record after the offset location in the bytestream

Throws:

IOException - thrown in a read error occurs

UnsupportedOperationException - thrown if not a random access file

getCount

public int getCount(int count)
             throws DataSourceException

Parses the shpfile counting the records.

Returns:

the number of non-null records in the shapefile

Throws:

DataSourceException

setHandler

public void setHandler(ShapeHandler handler)

Parameters:

handler - The handler to set.

id

public String id()

Description copied from interface: FileReader

An id for the reader. This is only used for debugging.

Specified by:

id in interface FileReader

Returns:

id for the reader.

setFlatGeometry

public void setFlatGeometry(boolean flatGeometry)