info.pppc.base.system

Class SystemID

java.lang.Object

info.pppc.base.system.SystemID

All Implemented Interfaces:

ISerializable

public final class SystemID
extends java.lang.Object
implements ISerializable

The system id identifies a single system. The actual identifier that is assigned to a system can be controlled via a system property. If this property is not set, the system identifier is generated randomly upon startup. Although, this is quite useful to simplify debugging, random identifiers are dangerous since there is a (small) chance that they might collide. Thus, it is safer to assign a system identifier manually when running actual applications.

Author:

Marcus Handte

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	ABBREVIATION The abbreviation used for this class during serialization.
static int	LENGTH The length of the byte array representation of the system id.
static SystemID	SYSTEM The id of the local system.

Constructor Summary

Constructors

Constructor and Description
SystemID() Creates a new uninitialized system id.
SystemID(byte[] id) Creates a system id from a byte sequence.
SystemID(long id) Creates a system id with the given id.

Method Summary

Methods

Modifier and Type	Method and Description
int	compareTo(SystemID id) Compares this system id with the specified system id and returns 0 if this id equals the system id, returns 1 if this id is larger than the system id and -1 if this id is smaller than the system id.
boolean	equals(java.lang.Object object) Determines whether this object equals the given object.
byte[]	getBytes() Returns a compact byte representation of the system id.
int	hashCode() Returns the hash code of this system id.
void	readObject(IObjectInput input) Reads the SystemID from a stream.
static void	setBytes(byte[] system) Sets the local system id.
static byte[]	toBytes(long value) Casts a long value to a byte array that has the length of the id array.
java.lang.String	toString() Returns a string representation.
static SystemID	valueOf(byte[] bytes) Converts a compact byte representation of a system id into a system id object.
void	writeObject(IObjectOutput output) Writes the SystemID to the given stream.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Field Detail

ABBREVIATION

public static final java.lang.String ABBREVIATION

The abbreviation used for this class during serialization.

See Also:

Constant Field Values

SYSTEM

public static final SystemID SYSTEM

The id of the local system. Currently, this value is created randomly. Actually, it should be configured manually outside of a development environment.

LENGTH

public static final int LENGTH

The length of the byte array representation of the system id. This is a global constant. The byte representations of all system ids will have the same length. At the present time this length is 8 (a single serialized long) however as it is not guaranteed that this length stays 8, users should always rely on this constant.

See Also:

Constant Field Values

Constructor Detail

SystemID

public SystemID()

Creates a new uninitialized system id. This constructor is solely intended for deserialization purposes. If you want to create a new system id, you must call the static create method.

SystemID

public SystemID(long id)

Creates a system id with the given id.

Parameters:

id - The id of the system id.

SystemID

public SystemID(byte[] id)

Creates a system id from a byte sequence. The byte sequence must have at least the length of LENGTH.

Parameters:

id - The byte sequence.

Method Detail

valueOf

public static SystemID valueOf(byte[] bytes)
                        throws java.lang.NumberFormatException

Converts a compact byte representation of a system id into a system id object.

Parameters:

bytes - The bytes that represent a system id.

Returns:

The system id represented by the byte array.

Throws:

java.lang.NumberFormatException - Thrown if the bytes do not represent a valid system id.

readObject

public void readObject(IObjectInput input)
                throws java.io.IOException

Reads the SystemID from a stream.

Specified by:

readObject in interface ISerializable

Parameters:

input - The stream to read from.

Throws:

java.io.IOException - Thrown if reading caused this exception.

writeObject

public void writeObject(IObjectOutput output)
                 throws java.io.IOException

Writes the SystemID to the given stream.

Specified by:

writeObject in interface ISerializable

Parameters:

output - The stream to write to.

Throws:

java.io.IOException - If writing to the stream caused an exception.

equals

public boolean equals(java.lang.Object object)

Determines whether this object equals the given object. For SystemIDs this method does not compare object equality, but id-based equality.

Overrides:

equals in class java.lang.Object

Parameters:

object - The object used for the comparison.

Returns:

True if the objects are equal or if two SystemIDs denote the same system.

compareTo

public int compareTo(SystemID id)

Compares this system id with the specified system id and returns 0 if this id equals the system id, returns 1 if this id is larger than the system id and -1 if this id is smaller than the system id. This method will throw a null pointer exception if the passed system id is null.

Parameters:

id - The system id to compare this id to.

Returns:

0 if equal, 1 if this is larger, -1 if this is smaller.

hashCode

public int hashCode()

Returns the hash code of this system id. This hash code solely depends on the denoted system.

Overrides:

hashCode in class java.lang.Object

Returns:

The hash code of the system.

toString

public java.lang.String toString()

Returns a string representation.

Overrides:

toString in class java.lang.Object

Returns:

A string representation.

getBytes

public byte[] getBytes()

Returns a compact byte representation of the system id. The length of this representation is constant for all system ids.

Returns:

A compact byte representation of the system id.

toBytes

public static final byte[] toBytes(long value)

Casts a long value to a byte array that has the length of the id array.

Parameters:

value - The value to cast.

Returns:

A byte array with the id array length.

setBytes

public static final void setBytes(byte[] system)

Sets the local system id. Warning, this method may only be called before the micro broker is booting up.

Parameters:

system - The byte representation of the local system id.