org.geotools.data.shape.shp
Class ShapefileReader

java.lang.Object
  org.geotools.data.shape.shp.ShapefileReader

public class ShapefileReader

extends java.lang.Object

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, Tommaso Nolli

Nested Class Summary

class

ShapefileReader.Record The reader returns only one Record instance in its lifetime.

Constructor Summary

ShapefileReader(java.nio.channels.ReadableByteChannel channel)
Default constructor.

ShapefileReader(java.nio.channels.ReadableByteChannel channel, boolean useMemoryMappedBuffer, boolean strict)
Creates a new instance of ShapeFile.

Method Summary

void	close() Clean up any resources.
int	getCount(int count) Parses the shpfile counting the records.
ShapefileHeader	getHeader() Get the header.
void	goTo(int offset)
boolean	hasNext() If there exists another record.
static void	main(java.lang.String[] args)
ShapefileReader.Record	nextRecord() Fetch the next record information.
static ShapefileHeader	readHeader(java.nio.channels.ReadableByteChannel channel, boolean strict) A short cut for reading the header from the given channel.
ShapefileReader.Record	recordAt(int offset) Sets the current location of the byteStream to offset and returns the next record.
java.lang.Object	shapeAt(int offset) TODO needs better java docs!!!
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 java.lang.Object

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

Constructor Detail

ShapefileReader

public ShapefileReader(java.nio.channels.ReadableByteChannel channel,
                       boolean useMemoryMappedBuffer,
                       boolean strict)
                throws java.io.IOException,
                       ShapefileException

Creates a new instance of ShapeFile.

Parameters:

channel - The ReadableByteChannel this reader will use.

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

Throws:

java.io.IOException - If problems arise.

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

ShapefileReader

public ShapefileReader(java.nio.channels.ReadableByteChannel channel)
                throws java.io.IOException,
                       ShapefileException

Default constructor. Calls ShapefileReader(channel,true).

Parameters:

channel -

Throws:

java.io.IOException

ShapefileException

Method Detail

readHeader

public static ShapefileHeader readHeader(java.nio.channels.ReadableByteChannel channel,
                                         boolean strict)
                                  throws java.io.IOException

A short cut for reading the header from the given channel.

Parameters:

channel - The channel to read from.

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

Returns:

A ShapefileHeader object.

Throws:

java.io.IOException - If problems arise.

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 java.io.IOException

Clean up any resources. Closes the channel.

Throws:

java.io.IOException - If errors occur while closing the channel.

supportsRandomAccess

public boolean supportsRandomAccess()

hasNext

public boolean hasNext()
                throws java.io.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:

java.io.IOException

transferTo

public int transferTo(ShapefileWriter writer,
                      int recordNum,
                      double[] bounds)
               throws java.io.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:

java.io.IOException

nextRecord

public ShapefileReader.Record nextRecord()
                                  throws java.io.IOException

Fetch the next record information.

Returns:

The record instance associated with this reader.

Throws:

java.io.IOException

goTo

public void goTo(int offset)
          throws java.io.IOException,
                 java.lang.UnsupportedOperationException

Parameters:

offset -

Throws:

java.io.IOException

java.lang.UnsupportedOperationException

shapeAt

public java.lang.Object shapeAt(int offset)
                         throws java.io.IOException,
                                java.lang.UnsupportedOperationException

TODO needs better java docs!!! What is offset?

Parameters:

offset -

Returns:

Throws:

java.io.IOException

java.lang.UnsupportedOperationException

recordAt

public ShapefileReader.Record recordAt(int offset)
                                throws java.io.IOException,
                                       java.lang.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.

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:

java.io.IOException - thrown in a read error occurs

java.lang.UnsupportedOperationException - thrown if not a random access file

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception

Throws:

java.lang.Exception

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