com.bloomberg.bmq

Class MessageGUID

java.lang.Object

com.bloomberg.bmq.MessageGUID

@Immutable
public class MessageGUID
extends Object

Provides a value-semantic global unique identifier for BlazingMQ messages.

MessageGUID provides a value-semantic global unique identifier for BlazingMQ messages. Each message delivered to BlazingMQ client from BlazingMQ broker contains a unique MessageGUID.

Externalization

For convenience, this class provides toHex method that can be used to externalize a MessageGUID instance. Applications can persist the resultant buffer (on filesystem, in database) to keep track of last processed message ID across task instantiations. fromHex method can be used to convert a valid externalized buffer back to a message ID.

Example 1: Externalizing

Below, msg is a valid instance of AckMessage obtained from an instance of AbstractSession via AckMessageHandler:

  MessageGUID g1 = msg.messageGUID();

  String hex1 = g1.toHex();

  assert MessageGUID.isValidHexRepresentation(hex1.getBytes());

  MessageGUID g2 = MessageGUID.fromHex(hex1);

  assert g1.equals(g2);
 

Field Summary

Fields

Modifier and Type	Field and Description
static int	SIZE_BINARY The size of a buffer needed to represent a GUID.
static int	SIZE_HEX The size of a hexadecimal string representation of the GUID.

Method Summary

Modifier and Type	Method and Description
static MessageGUID	createEmptyGUID() Returns a zero filled MessageGUID object.
boolean	equals(Object other) Returns true if this GUID is equal to the specified other, false otherwise.
static MessageGUID	fromBinary(byte[] buffer) Returns a new MessageGUID created from the specified buffer, in binary format.
static MessageGUID	fromHex(String val) Returns a new MessageGUID created from the specified String contained hexadecimal representation of the GUID.
int	hashCode() Returns a hash code value for this MessageGUID object.
static boolean	isValidHexRepresentation(byte[] buffer) Returns true if the specified buffer is a valid hex representation of a MessageGUID.
void	toBinary(byte[] destination) Writes a binary representation of this object to the specified destination which length should be SIZE_BINARY.
String	toHex() Returns a hex representation of this object as a String.
String	toString() Returns a hex representation of this object as a String.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

SIZE_BINARY

public static final int SIZE_BINARY

The size of a buffer needed to represent a GUID.

See Also:

Constant Field Values

SIZE_HEX

public static final int SIZE_HEX

The size of a hexadecimal string representation of the GUID.

See Also:

Constant Field Values

Method Detail

isValidHexRepresentation

public static boolean isValidHexRepresentation(byte[] buffer)

Returns true if the specified buffer is a valid hex representation of a MessageGUID. The the buffer should be equal to SIZE_HEX.

Parameters:

buffer - Array of bytes that contrains hex representation the MessageGUID.

Returns:

boolean true if the specified buffer is a valid hex representation, false otherwise.

Throws:

NullPointerException - if the specified buffer is null

toBinary

public void toBinary(byte[] destination)

Writes a binary representation of this object to the specified destination which length should be SIZE_BINARY. Note that destination can later be used to populate a MessageGUID object using fromBinary(byte[]) method.

Parameters:

destination - byte array to store a binary representation of this GUID

Throws:

IllegalArgumentException - in case of the destination length is less than SIZE_BINARY

NullPointerException - if the specified destination is null

toHex

public String toHex()

Returns a hex representation of this object as a String. Note that the returned string can later be used to create a MessageGUID object using fromHex method.

Returns:

String hex representation of this object

fromBinary

public static MessageGUID fromBinary(byte[] buffer)

Returns a new MessageGUID created from the specified buffer, in binary format. The buffer length should be SIZE_BINARY.

Parameters:

buffer - binary representation of the GUID

Returns:

MessageGUID newly created MessageGUID object

Throws:

IllegalArgumentException - in case of the buffer length is less than SIZE_BINARY

NullPointerException - if the specified buffer is null

fromHex

public static MessageGUID fromHex(String val)

Returns a new MessageGUID created from the specified String contained hexadecimal representation of the GUID.

Parameters:

val - string with a hexadecimal representation of the GUID

Returns:

MessageGUID newly created MessageGUID object

Throws:

IllegalArgumentException - in case of the specified string is not a valid hexadecimal representation of the GUID, or if error happens during string decoding

NullPointerException - if the specified val is null

createEmptyGUID

public static MessageGUID createEmptyGUID()

Returns a zero filled MessageGUID object.

Returns:

MessageGUID zero message GUID

toString

public String toString()

Returns a hex representation of this object as a String.

Overrides:

toString in class Object

Returns:

String hex representation of this object

equals

public boolean equals(Object other)

Returns true if this GUID is equal to the specified other, false otherwise. Two GUIDs are equal if they have equal binary representations.

Overrides:

equals in class Object

Parameters:

other - GUID object to compare with

Returns:

boolean true if GUIDs are equal, false otherwise

hashCode

public int hashCode()

Returns a hash code value for this MessageGUID object.

Overrides:

hashCode in class Object

Returns:

int a hash code value for this object.