py4j

Class Protocol

java.lang.Object

py4j.Protocol

public class Protocol
extends Object

This class defines the protocol used to communicate between two virtual machines (e.g., Python and Java).

Currently, the protocol requires type information (e.g., is this string an integer, an object reference or a boolean?) to be embedded with each command part. The rational is that the source virtual machine is usually better at determining the type of objects it sends.

An input command is usually composed of:

• A command name (e.g., c for call)
• Optionally, a sub command name (e.g., 'a' for concatenate in the list command)
• A list of command parts (e.g., the name of a method, the value of a parameter, etc.)
• The End of Command marker (e)

The various parts of a command are separated by \n characters. These characters are automatically escaped and unescaped in Strings on both sides (Java and Python).

An output command is usually composed of:

• A success or error code (y for yes, x for exception)
• A return value (e.g., n for null, v for void, or any other value like a String)

This class should be used only if the user creates new commands.

Author:

Barthelemy Dagenais

Field Summary

Fields

Modifier and Type	Field and Description
static char	ARRAY_TYPE
static char	BOOLEAN_TYPE
static char	BYTES_TYPE
static char	CLASS_TYPE
static char	DECIMAL_TYPE
static String	DEFAULT_JVM_OBJECT_ID
static char	DOUBLE_TYPE
static char	END
static char	END_OUTPUT
static String	ENTRY_POINT_OBJECT_ID
static char	ERROR
static String	ERROR_COMMAND
static char	INTEGER_TYPE
static char	ITERATOR_TYPE
static char	LIST_TYPE
static char	LONG_TYPE
static char	MAP_TYPE
static char	METHOD_TYPE
static char	NO_MEMBER
static String	NO_SUCH_FIELD
static char	NULL_TYPE
static char	PACKAGE_TYPE
static String	PYTHON_INFINITY
static String	PYTHON_NAN
static String	PYTHON_NEGATIVE_INFINITY
static char	PYTHON_PROXY_TYPE
static char	REFERENCE_TYPE
static char	RETURN_MESSAGE
static char	SET_TYPE
static String	STATIC_PREFIX
static char	STRING_TYPE
static char	SUCCESS
static char	VOID
static String	VOID_COMMAND

Constructor Summary

Constructors

Constructor and Description
Protocol()

Method Summary

Modifier and Type	Method and Description
static String	encodeBytes(byte[] bytes) Transform the byte array into Base64 characters.
static boolean	getBoolean(String commandPart) Assumes that commandPart is not empty.
static byte[]	getBytes(String commandPart) Assumes that commandPart is not empty.
static BigDecimal	getDecimal(String commandPart) Assumes that commandPart is not empty.
static double	getDouble(String commandPart) Assumes that commandPart is not empty.
static int	getInteger(String commandPart) Assumes that commandPart is not empty.
static long	getLong(String commandPart) Assumes that commandPart is not empty.
static String	getMemberOutputCommand(char memberType)
static String	getMemberOutputCommand(char memberType, String fqn)
static String	getNoSuchFieldOutputCommand()
static Object	getNull(String commandPart) Method provided for consistency.
static Object	getObject(String commandPart, Gateway gateway)
static String	getOutputCommand(ReturnObject rObject)
static String	getOutputErrorCommand()
static String	getOutputErrorCommand(String errorMessage)
static String	getOutputErrorCommand(Throwable throwable)
static String	getOutputVoidCommand()
static char	getPrimitiveType(Object primitiveObject)
static Object	getPythonProxy(String commandPart, Gateway gateway) Assumes that commandPart is not empty.
static Object	getPythonProxyHandler(ClassLoader classLoader, Class[] interfacesToImplement, String objectId, Gateway gateway)
static Object	getReference(String commandPart, Gateway gateway) Assumes that commandPart is not empty.
static Object	getReturnValue(String returnMessage, Gateway gateway)
static Throwable	getRootThrowable(Throwable throwable, boolean skipInvocation)
static String	getString(String commandPart) Assumes that commandPart is not empty.
static String	getThrowableAsString(Throwable throwable)
static boolean	isBoolean(String commandPart) Assumes that commandPart is not empty.
static boolean	isBytes(String commandPart) Assumes that commandPart is not empty.
static boolean	isDecimal(String commandPart) Assumes that commandPart is not empty.
static boolean	isDouble(String commandPart) Assumes that commandPart is not empty.
static boolean	isEmpty(String commandPart)
static boolean	isEnd(String commandPart) Assumes that commandPart is not empty.
static boolean	isError(String returnMessage) Assumes that commandPart is not null.
static boolean	isInteger(String commandPart) Assumes that commandPart is not empty.
static boolean	isLong(String commandPart) Assumes that commandPart is not empty.
static boolean	isNull(String commandPart) Assumes that commandPart is not empty.
static boolean	isPythonProxy(String commandPart) Assumes that commandPart is not empty.
static boolean	isReference(String commandPart) Assumes that commandPart is not empty.
static boolean	isReturnMessage(String commandPart)
static boolean	isString(String commandPart) Assumes that commandPart is not empty.

Methods inherited from class java.lang.Object

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

Field Detail

BYTES_TYPE

public static final char BYTES_TYPE

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Constant Field Values

INTEGER_TYPE

public static final char INTEGER_TYPE

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LONG_TYPE

public static final char LONG_TYPE

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Constant Field Values

BOOLEAN_TYPE

public static final char BOOLEAN_TYPE

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DOUBLE_TYPE

public static final char DOUBLE_TYPE

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DECIMAL_TYPE

public static final char DECIMAL_TYPE

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STRING_TYPE

public static final char STRING_TYPE

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REFERENCE_TYPE

public static final char REFERENCE_TYPE

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Constant Field Values

LIST_TYPE

public static final char LIST_TYPE

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SET_TYPE

public static final char SET_TYPE

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ARRAY_TYPE

public static final char ARRAY_TYPE

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MAP_TYPE

public static final char MAP_TYPE

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ITERATOR_TYPE

public static final char ITERATOR_TYPE

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NULL_TYPE

public static final char NULL_TYPE

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PYTHON_PROXY_TYPE

public static final char PYTHON_PROXY_TYPE

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PACKAGE_TYPE

public static final char PACKAGE_TYPE

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CLASS_TYPE

public static final char CLASS_TYPE

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METHOD_TYPE

public static final char METHOD_TYPE

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NO_MEMBER

public static final char NO_MEMBER

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VOID

public static final char VOID

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Constant Field Values

RETURN_MESSAGE

public static final char RETURN_MESSAGE

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Constant Field Values

END

public static final char END

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END_OUTPUT

public static final char END_OUTPUT

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ERROR

public static final char ERROR

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SUCCESS

public static final char SUCCESS

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ERROR_COMMAND

public static final String ERROR_COMMAND

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VOID_COMMAND

public static final String VOID_COMMAND

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NO_SUCH_FIELD

public static final String NO_SUCH_FIELD

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ENTRY_POINT_OBJECT_ID

public static final String ENTRY_POINT_OBJECT_ID

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DEFAULT_JVM_OBJECT_ID

public static final String DEFAULT_JVM_OBJECT_ID

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STATIC_PREFIX

public static final String STATIC_PREFIX

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PYTHON_NAN

public static final String PYTHON_NAN

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PYTHON_INFINITY

public static final String PYTHON_INFINITY

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Constant Field Values

PYTHON_NEGATIVE_INFINITY

public static final String PYTHON_NEGATIVE_INFINITY

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Constant Field Values

Constructor Detail

Protocol

public Protocol()

Method Detail

encodeBytes

public static String encodeBytes(byte[] bytes)

Transform the byte array into Base64 characters.

Parameters:

bytes -

Returns:

getBoolean

public static final boolean getBoolean(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The boolean value corresponding to this command part.

getBytes

public static final byte[] getBytes(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The byte array corresponding to this command part.

getDecimal

public static final BigDecimal getDecimal(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The decimal value corresponding to this command part.

getDouble

public static final double getDouble(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The double value corresponding to this command part.

getInteger

public static final int getInteger(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The integer value corresponding to this command part.

getLong

public static final long getLong(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The long value corresponding to this command part.

getMemberOutputCommand

public static final String getMemberOutputCommand(char memberType)

getMemberOutputCommand

public static final String getMemberOutputCommand(char memberType,
                                                  String fqn)

getNoSuchFieldOutputCommand

public static String getNoSuchFieldOutputCommand()

getNull

public static final Object getNull(String commandPart)

Method provided for consistency. Just returns null.

Parameters:

commandPart -

Returns:

null.

getObject

public static final Object getObject(String commandPart,
                                     Gateway gateway)

getOutputCommand

public static final String getOutputCommand(ReturnObject rObject)

getOutputErrorCommand

public static final String getOutputErrorCommand()

getOutputErrorCommand

public static final String getOutputErrorCommand(String errorMessage)

getOutputErrorCommand

public static final String getOutputErrorCommand(Throwable throwable)

getOutputVoidCommand

public static final String getOutputVoidCommand()

getPrimitiveType

public static char getPrimitiveType(Object primitiveObject)

getPythonProxy

public static Object getPythonProxy(String commandPart,
                                    Gateway gateway)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

A Python proxy specified in this command part.

getPythonProxyHandler

public static Object getPythonProxyHandler(ClassLoader classLoader,
                                           Class[] interfacesToImplement,
                                           String objectId,
                                           Gateway gateway)

getReference

public static final Object getReference(String commandPart,
                                        Gateway gateway)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The object referenced in this command part.

getReturnValue

public static final Object getReturnValue(String returnMessage,
                                          Gateway gateway)

getRootThrowable

public static final Throwable getRootThrowable(Throwable throwable,
                                               boolean skipInvocation)

getString

public static final String getString(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

The reference contained in this command part.

getThrowableAsString

public static final String getThrowableAsString(Throwable throwable)

isBoolean

public static final boolean isBoolean(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a boolean

isReturnMessage

public static final boolean isReturnMessage(String commandPart)

Parameters:

commandPart -

Returns:

True if the command part is a return message

isBytes

public static final boolean isBytes(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a byte array

isDecimal

public static final boolean isDecimal(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a decimal

isDouble

public static final boolean isDouble(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a double

isEmpty

public static final boolean isEmpty(String commandPart)

isEnd

public static final boolean isEnd(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is the end token

isError

public static final boolean isError(String returnMessage)

Assumes that commandPart is not null.

Parameters:

returnMessage -

Returns:

True if the return message is an error

isInteger

public static final boolean isInteger(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is an integer

isLong

public static final boolean isLong(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a long

isNull

public static final boolean isNull(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is null

isPythonProxy

public static final boolean isPythonProxy(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a python proxy

isReference

public static final boolean isReference(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a reference

isString

public static final boolean isString(String commandPart)

Assumes that commandPart is not empty.

Parameters:

commandPart -

Returns:

True if the command part is a reference