Package org.apache.hadoop.fs.shell

Class CommandFactory

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.hadoop.fs.shell.CommandFactory

All Implemented Interfaces:

Configurable

@Private
@Unstable
public class CommandFactory
extends Configured

class to search for and register commands

Constructor Summary

Constructors

Constructor	Description
CommandFactory()	Factory constructor for commands
CommandFactory(Configuration conf)	Factory constructor for commands

Method Summary

Modifier and Type	Method	Description
void	addClass(java.lang.Class<? extends Command> cmdClass, java.lang.String... names)	Register the given class as handling the given list of command names.
void	addObject(Command cmdObject, java.lang.String... names)	Register the given object as handling the given list of command names.
Command	getInstance(java.lang.String cmd)	Returns an instance of the class implementing the given command.
Command	getInstance(java.lang.String cmdName, Configuration conf)	Get an instance of the requested command
java.lang.String[]	getNames()	Gets all of the registered commands
void	registerCommands(java.lang.Class<?> registrarClass)	Invokes "static void registerCommands(CommandFactory)" on the given class.

Methods inherited from class org.apache.hadoop.conf.Configured

getConf, setConf

Methods inherited from class java.lang.Object

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

Constructor Detail

CommandFactory

public CommandFactory()

Factory constructor for commands

CommandFactory

public CommandFactory(Configuration conf)

Factory constructor for commands

Parameters:

conf - the hadoop configuration

Method Detail

registerCommands

public void registerCommands(java.lang.Class<?> registrarClass)

Invokes "static void registerCommands(CommandFactory)" on the given class. This method abstracts the contract between the factory and the command class. Do not assume that directly invoking registerCommands on the given class will have the same effect.

Parameters:

registrarClass - class to allow an opportunity to register

addClass

public void addClass(java.lang.Class<? extends Command> cmdClass,
                     java.lang.String... names)

Register the given class as handling the given list of command names.

Parameters:

cmdClass - the class implementing the command names

names - one or more command names that will invoke this class

addObject

public void addObject(Command cmdObject,
                      java.lang.String... names)

Register the given object as handling the given list of command names. Avoid calling this method and use addClass(Class, String...) whenever possible to avoid startup overhead from excessive command object instantiations. This method is intended only for handling nested non-static classes that are re-usable. Namely -help/-usage.

Parameters:

cmdObject - the object implementing the command names

names - one or more command names that will invoke this class

getInstance

public Command getInstance(java.lang.String cmd)

Returns an instance of the class implementing the given command. The class must have been registered via addClass(Class, String...)

Parameters:

cmd - name of the command

Returns:

instance of the requested command

getInstance

public Command getInstance(java.lang.String cmdName,
                           Configuration conf)

Get an instance of the requested command

Parameters:

cmdName - name of the command to lookup

conf - the hadoop configuration

Returns:

the Command or null if the command is unknown

getNames

public java.lang.String[] getNames()

Gets all of the registered commands

Returns:

a sorted list of command names