org.apache.hadoop.util

Class FindClass

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.hadoop.util.FindClass

All Implemented Interfaces:

Configurable, Tool

public final class FindClass
extends Configured
implements Tool

This entry point exists for diagnosing classloader problems: is a class or resource present -and if so, where?

Actions

• load

  : load a class but do not attempt to create it

• create

  : load and create a class, print its string value

• printresource

  : load a resource then print it to stdout

• resource

  : load a resource then print the URL of that resource

It returns an error code if a class/resource cannot be loaded/found -and optionally a class may be requested as being loaded. The latter action will call the class's constructor -it must support an empty constructor); any side effects from the constructor or static initializers will take place. All error messages are printed to System.out; errors to System.err.

Field Summary

Fields

Modifier and Type	Field and Description
static String	A_CREATE create command: "create"
static String	A_LOAD Load command: "load"
static String	A_PRINTRESOURCE Command to locate and print a resource: "print"
static String	A_RESOURCE Command to locate a resource: "locate"
protected static int	E_CREATE_FAILED class creation failed 5
protected static int	E_GENERIC generic error 1
protected static int	E_LOAD_FAILED class load failed 4
protected static int	E_NOT_FOUND class or resource not found 3
protected static int	E_USAGE usage error -bad arguments or similar 2
static int	SUCCESS Exit code when the operation succeeded: 0

Constructor Summary

Constructors

Constructor and Description
FindClass() Empty constructor; passes a new Configuration object instance to its superclass's constructor
FindClass(Configuration conf) Create a class with a specified configuration

Method Summary

Modifier and Type	Method and Description
static void	main(String[] args) Main entry point.
int	run(String[] args) Run the class/resource find or load operation
static void	setOutputStreams(PrintStream out, PrintStream err) Change the output streams to be something other than the System.out and System.err streams

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

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Field Detail

A_CREATE

public static final String A_CREATE

create command: "create"

See Also:

Constant Field Values

A_LOAD

public static final String A_LOAD

Load command: "load"

See Also:

Constant Field Values

A_RESOURCE

public static final String A_RESOURCE

Command to locate a resource: "locate"

See Also:

Constant Field Values

A_PRINTRESOURCE

public static final String A_PRINTRESOURCE

Command to locate and print a resource: "print"

See Also:

Constant Field Values

SUCCESS

public static final int SUCCESS

Exit code when the operation succeeded: 0

See Also:

Constant Field Values

E_GENERIC

protected static final int E_GENERIC

generic error 1

See Also:

Constant Field Values

E_USAGE

protected static final int E_USAGE

usage error -bad arguments or similar 2

See Also:

Constant Field Values

E_NOT_FOUND

protected static final int E_NOT_FOUND

class or resource not found 3

See Also:

Constant Field Values

E_LOAD_FAILED

protected static final int E_LOAD_FAILED

class load failed 4

See Also:

Constant Field Values

E_CREATE_FAILED

protected static final int E_CREATE_FAILED

class creation failed 5

See Also:

Constant Field Values

Constructor Detail

FindClass

public FindClass()

Empty constructor; passes a new Configuration object instance to its superclass's constructor

FindClass

public FindClass(Configuration conf)

Create a class with a specified configuration

Parameters:

conf - configuration

Method Detail

setOutputStreams

public static void setOutputStreams(PrintStream out,
                                    PrintStream err)

Change the output streams to be something other than the System.out and System.err streams

Parameters:

out - new stdout stream

err - new stderr stream

run

public int run(String[] args)
        throws Exception

Run the class/resource find or load operation

Specified by:

run in interface Tool

Parameters:

args - command specific arguments.

Returns:

the outcome

Throws:

Exception - if something went very wrong

main

public static void main(String[] args)

Main entry point. Runs the class via the ToolRunner, then exits with an appropriate exit code.

Parameters:

args - argument list