org.apache.hadoop.io.compress
Class CompressionCodecFactory

java.lang.Object
  org.apache.hadoop.io.compress.CompressionCodecFactory

@InterfaceAudience.Public
@InterfaceStability.Evolving
public class CompressionCodecFactory
extends Object

A factory that will find the correct codec for a given filename.

Field Summary

static org.apache.commons.logging.Log

LOG

Constructor Summary

CompressionCodecFactory(Configuration conf)
Find the codecs specified in the config value io.compression.codecs and register them.

Method Summary

CompressionCodec	getCodec(Path file) Find the relevant compression codec for the given file based on its filename suffix.
CompressionCodec	getCodecByClassName(String classname) Find the relevant compression codec for the codec's canonical class name.
CompressionCodec	getCodecByName(String codecName) Find the relevant compression codec for the codec's canonical class name or by codec alias.
Class<? extends CompressionCodec>	getCodecClassByName(String codecName) Find the relevant compression codec for the codec's canonical class name or by codec alias and returns its implemetation class.
static List<Class<? extends CompressionCodec>>	getCodecClasses(Configuration conf) Get the list of codecs discovered via a Java ServiceLoader, or listed in the configuration.
static void	main(String[] args) A little test program.
static String	removeSuffix(String filename, String suffix) Removes a suffix from a filename, if it has it.
static void	setCodecClasses(Configuration conf, List<Class> classes) Sets a list of codec classes in the configuration.
String	toString() Print the extension map out as a string.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

public static final org.apache.commons.logging.Log LOG

Constructor Detail

CompressionCodecFactory

public CompressionCodecFactory(Configuration conf)

Find the codecs specified in the config value io.compression.codecs and register them. Defaults to gzip and deflate.

Method Detail

toString

public String toString()

Print the extension map out as a string.

Overrides:

toString in class Object

getCodecClasses

public static List<Class<? extends CompressionCodec>> getCodecClasses(Configuration conf)

Get the list of codecs discovered via a Java ServiceLoader, or listed in the configuration. Codecs specified in configuration come later in the returned list, and are considered to override those from the ServiceLoader.

Parameters:

conf - the configuration to look in

Returns:

a list of the CompressionCodec classes

setCodecClasses

public static void setCodecClasses(Configuration conf,
                                   List<Class> classes)

Sets a list of codec classes in the configuration. In addition to any classes specified using this method, CompressionCodec classes on the classpath are discovered using a Java ServiceLoader.

Parameters:

conf - the configuration to modify

classes - the list of classes to set

getCodec

public CompressionCodec getCodec(Path file)

Find the relevant compression codec for the given file based on its filename suffix.

Parameters:

file - the filename to check

Returns:

the codec object

getCodecByClassName

public CompressionCodec getCodecByClassName(String classname)

Find the relevant compression codec for the codec's canonical class name.

Parameters:

classname - the canonical class name of the codec

Returns:

the codec object

getCodecByName

public CompressionCodec getCodecByName(String codecName)

Find the relevant compression codec for the codec's canonical class name or by codec alias.

Codec aliases are case insensitive.

The code alias is the short class name (without the package name). If the short class name ends with 'Codec', then there are two aliases for the codec, the complete short class name and the short class name without the 'Codec' ending. For example for the 'GzipCodec' codec class name the alias are 'gzip' and 'gzipcodec'.

Parameters:

codecName - the canonical class name of the codec

Returns:

the codec object

getCodecClassByName

public Class<? extends CompressionCodec> getCodecClassByName(String codecName)

Find the relevant compression codec for the codec's canonical class name or by codec alias and returns its implemetation class.

Codec aliases are case insensitive.

The code alias is the short class name (without the package name). If the short class name ends with 'Codec', then there are two aliases for the codec, the complete short class name and the short class name without the 'Codec' ending. For example for the 'GzipCodec' codec class name the alias are 'gzip' and 'gzipcodec'.

Parameters:

codecName - the canonical class name of the codec

Returns:

the codec class

removeSuffix

public static String removeSuffix(String filename,
                                  String suffix)

Removes a suffix from a filename, if it has it.

Parameters:

filename - the filename to strip

suffix - the suffix to remove

Returns:

the shortened filename

main

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

A little test program.

Parameters:

args -

Throws:

Exception