java.rmi.server
Class ObjID

java.lang.Object
  java.rmi.server.ObjID

All Implemented Interfaces:

Serializable

public final class ObjID

extends Object

implements Serializable

An ObjID is used to identify a remote object exported to an RMI runtime. When a remote object is exported, it is assigned an object identifier either implicitly or explicitly, depending on the API used to export.

The ObjID() constructor can be used to generate a unique object identifier. Such an ObjID is unique over time with respect to the host it is generated on. The ObjID(int) constructor can be used to create a "well-known" object identifier. The scope of a well-known ObjID depends on the RMI runtime it is exported to.

An ObjID instance contains an object number (of type long) and an address space identifier (of type UID). In a unique ObjID, the address space identifier is unique with respect to a given host over time. In a well-known ObjID, the address space identifier is equivalent to one returned by invoking the UID.UID(short) constructor with the value zero.

If the system property java.rmi.server.randomIDs is defined to equal the string "true" (case insensitive), then the ObjID() constructor will use a cryptographically strong random number generator to choose the object number of the returned ObjID.

Since:

JDK1.1

Author:

Ann Wollrath, Peter Jones

See Also:

Serialized Form

Nested Class Summary

private static class

ObjID.InsecureRandom

Field Summary

static int	ACTIVATOR_ID Object number for well-known ObjID of the activator.
static int	DGC_ID Object number for well-known ObjID of the distributed garbage collector.
private static Random	generator
private static UID	mySpace
private long	objNum
static int	REGISTRY_ID Object number for well-known ObjID of the registry.
private static long	serialVersionUID indicate compatibility with JDK 1.1.x version of class
private UID	space

Constructor Summary

	ObjID() Generates a unique object identifier.
	ObjID(int objNum) Creates a "well-known" object identifier.
private	ObjID(long objNum, UID space) Constructs an object identifier given data read from a stream.

Method Summary

boolean	equals(Object obj) Compares the specified object with this ObjID for equality.
int	hashCode() Returns the hash code value for this object identifier, the object number.
static ObjID	read(ObjectInput in) Constructs and returns a new ObjID instance by unmarshalling a binary representation from an ObjectInput instance.
String	toString() Returns a string representation of this object identifier.
void	write(ObjectOutput out) Marshals a binary representation of this ObjID to an ObjectOutput instance.

Methods inherited from class java.lang.Object

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

Field Detail

REGISTRY_ID

public static final int REGISTRY_ID

Object number for well-known ObjID of the registry.

See Also:

Constant Field Values

ACTIVATOR_ID

public static final int ACTIVATOR_ID

Object number for well-known ObjID of the activator.

See Also:

Constant Field Values

DGC_ID

public static final int DGC_ID

Object number for well-known ObjID of the distributed garbage collector.

See Also:

Constant Field Values

serialVersionUID

private static final long serialVersionUID

indicate compatibility with JDK 1.1.x version of class

See Also:

Constant Field Values

mySpace

private static final UID mySpace

generator

private static final Random generator

objNum

private final long objNum

See Also:

hashCode()

space

private final UID space

Constructor Detail

ObjID

public ObjID()

Generates a unique object identifier.

If the system property java.rmi.server.randomIDs is defined to equal the string "true" (case insensitive), then this constructor will use a cryptographically strong random number generator to choose the object number of the returned ObjID.

ObjID

public ObjID(int objNum)

Creates a "well-known" object identifier.

An ObjID created via this constructor will not clash with any ObjIDs generated via the no-arg constructor.

Parameters:

objNum - object number for well-known object identifier

ObjID

private ObjID(long objNum,
              UID space)

Constructs an object identifier given data read from a stream.

Method Detail

write

public void write(ObjectOutput out)
           throws IOException

Marshals a binary representation of this ObjID to an ObjectOutput instance.

Specifically, this method first invokes the given stream's DataOutput.writeLong(long) method with this object identifier's object number, and then it writes its address space identifier by invoking its UID.write(DataOutput) method with the stream.

Parameters:

out - the ObjectOutput instance to write this ObjID to

Throws:

IOException - if an I/O error occurs while performing this operation

read

public static ObjID read(ObjectInput in)
                  throws IOException

Constructs and returns a new ObjID instance by unmarshalling a binary representation from an ObjectInput instance.

Specifically, this method first invokes the given stream's DataInput.readLong() method to read an object number, then it invokes UID.read(DataInput) with the stream to read an address space identifier, and then it creates and returns a new ObjID instance that contains the object number and address space identifier that were read from the stream.

Parameters:

in - the ObjectInput instance to read ObjID from

Returns:

unmarshalled ObjID instance

Throws:

IOException - if an I/O error occurs while performing this operation

hashCode

public int hashCode()

Returns the hash code value for this object identifier, the object number.

Overrides:

hashCode in class Object

Returns:

the hash code value for this object identifier

See Also:

Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object obj)

Compares the specified object with this ObjID for equality. This method returns true if and only if the specified object is an ObjID instance with the same object number and address space identifier as this one.

Overrides:

equals in class Object

Parameters:

obj - the object to compare this ObjID to

Returns:

true if the given object is equivalent to this one, and false otherwise

See Also:

Object.hashCode(), Hashtable

toString

public String toString()

Returns a string representation of this object identifier.

Overrides:

toString in class Object

Returns:

a string representation of this object identifier