org.apache.avro.file

Class DataFileReader<D>

java.lang.Object

org.apache.avro.file.DataFileStream<D>

org.apache.avro.file.DataFileReader<D>

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<D>, Iterator<D>, FileReader<D>

public class DataFileReader<D>
extends DataFileStream<D>
implements FileReader<D>

Random access to files written with DataFileWriter.

See Also:

DataFileWriter

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.avro.file.DataFileStream

DataFileStream.Header

Constructor Summary

Constructors

Modifier	Constructor and Description
	DataFileReader(File file, DatumReader<D> reader) Construct a reader for a file.
	DataFileReader(SeekableInput sin, DatumReader<D> reader) Construct a reader for a file.
protected	DataFileReader(SeekableInput sin, DatumReader<D> reader, boolean closeOnError, byte[] magic) Construct a reader for a file.
protected	DataFileReader(SeekableInput sin, DatumReader<D> reader, DataFileStream.Header header) Construct using a DataFileStream.Header.

Method Summary

Modifier and Type	Method and Description
protected void	blockFinished()
static <D> FileReader<D>	openReader(File file, DatumReader<D> reader) Open a reader for a file.
static <D> FileReader<D>	openReader(SeekableInput in, DatumReader<D> reader) Open a reader for a file.
static <D> DataFileReader<D>	openReader(SeekableInput in, DatumReader<D> reader, DataFileStream.Header header, boolean sync) Construct a reader for a file at the current position of the input, without reading the header.
boolean	pastSync(long position) Return true if past the next synchronization point after a position.
long	previousSync() Return the last synchronization point before our current position.
void	seek(long position) Move to a specific, known synchronization point, one returned from DataFileWriter.sync() while writing.
void	sync(long position) Move to the next synchronization point after a position.
long	tell() Return the current position in the input.

Methods inherited from class org.apache.avro.file.DataFileStream

close, getBlockCount, getBlockSize, getHeader, getMeta, getMetaKeys, getMetaLong, getMetaString, getSchema, hasNext, iterator, next, next, nextBlock, remove

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.avro.file.FileReader

getSchema, next

Methods inherited from interface java.util.Iterator

forEachRemaining, hasNext, next, remove

Methods inherited from interface java.lang.Iterable

forEach, iterator, spliterator

Methods inherited from interface java.io.Closeable

close

Constructor Detail

DataFileReader

public DataFileReader(File file,
                      DatumReader<D> reader)
               throws IOException

Construct a reader for a file. For example,if you want to read a file record,you need to close the resource. You can use try-with-resource as follows:

 try (FileReader dataFileReader =
 DataFileReader.openReader(file,datumReader)) { //Consume the reader } catch
 (IOException e) { throw new RunTimeIOException(e,"Failed to read metadata for
 file: %s", file); }

 

Throws:

IOException

DataFileReader

public DataFileReader(SeekableInput sin,
                      DatumReader<D> reader)
               throws IOException

Construct a reader for a file. For example,if you want to read a file record,you need to close the resource. You can use try-with-resource as follows:

 try (FileReader dataFileReader =
 DataFileReader.openReader(file,datumReader)) { //Consume the reader } catch
 (IOException e) { throw new RunTimeIOException(e,"Failed to read metadata for
 file: %s", file); }

 

Throws:

IOException

DataFileReader

protected DataFileReader(SeekableInput sin,
                         DatumReader<D> reader,
                         boolean closeOnError,
                         byte[] magic)
                  throws IOException

Construct a reader for a file. Please close resource files yourself.

Throws:

IOException

DataFileReader

protected DataFileReader(SeekableInput sin,
                         DatumReader<D> reader,
                         DataFileStream.Header header)
                  throws IOException

Construct using a DataFileStream.Header. Does not call sync(long) or seek(long).

Throws:

IOException

Method Detail

openReader

public static <D> FileReader<D> openReader(File file,
                                           DatumReader<D> reader)
                                    throws IOException

Open a reader for a file.

Throws:

IOException

openReader

public static <D> FileReader<D> openReader(SeekableInput in,
                                           DatumReader<D> reader)
                                    throws IOException

Open a reader for a file.

Throws:

IOException

openReader

public static <D> DataFileReader<D> openReader(SeekableInput in,
                                               DatumReader<D> reader,
                                               DataFileStream.Header header,
                                               boolean sync)
                                        throws IOException

Construct a reader for a file at the current position of the input, without reading the header.

Parameters:

sync - True to read forward to the next sync point after opening, false to assume that the input is already at a valid sync point.

Throws:

IOException

seek

public void seek(long position)
          throws IOException

Move to a specific, known synchronization point, one returned from DataFileWriter.sync() while writing. If synchronization points were not saved while writing a file, use sync(long) instead.

Throws:

IOException

sync

public void sync(long position)
          throws IOException

Move to the next synchronization point after a position. To process a range of file entires, call this with the starting position, then check pastSync(long) with the end point before each call to DataFileStream.next().

Specified by:

sync in interface FileReader<D>

Throws:

IOException

blockFinished

protected void blockFinished()
                      throws IOException

Overrides:

blockFinished in class DataFileStream<D>

Throws:

IOException

previousSync

public long previousSync()

Return the last synchronization point before our current position.

pastSync

public boolean pastSync(long position)
                 throws IOException

Return true if past the next synchronization point after a position.

Specified by:

pastSync in interface FileReader<D>

Throws:

IOException

tell

public long tell()
          throws IOException

Description copied from interface: FileReader

Return the current position in the input.

Specified by:

tell in interface FileReader<D>

Throws:

IOException