java.rmi.server: public final class: ObjID

java.rmi.server
public final class: ObjID [javadoc | source]

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

All Implemented Interfaces:
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.

author: Ann - Wollrath

author: Peter - Jones

since: JDK1.1 -

Field Summary
public static final int	REGISTRY_ID	Object number for well-known `ObjID` of the registry.
public static final int	ACTIVATOR_ID	Object number for well-known `ObjID` of the activator.
public static final int	DGC_ID	Object number for well-known `ObjID` of the distributed garbage collector.

Constructor:

Constructor:
public ObjID() { /* * If generating random object numbers, create a new UID to * ensure uniqueness; otherwise, use a shared UID because * sequential object numbers already ensure uniqueness. */ if (useRandomIDs()) { space = new UID(); objNum = secureRandom.nextLong(); } else { space = mySpace; objNum = nextObjNum.getAndIncrement(); } } 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`.
public ObjID(int objNum) { space = new UID((short) 0); this.objNum = objNum; } Creates a "well-known" object identifier. An `ObjID` created via this constructor will not clash with any `ObjID`s generated via the no-arg constructor. Parameters: `objNum` - object number for well-known object identifier

 public ObjID() {
        /*
         * If generating random object numbers, create a new UID to
         * ensure uniqueness; otherwise, use a shared UID because
         * sequential object numbers already ensure uniqueness.
         */
        if (useRandomIDs()) {
            space = new UID();
            objNum = secureRandom.nextLong();
        } else {
            space = mySpace;
            objNum = nextObjNum.getAndIncrement();
        }
}

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.

 public ObjID(int objNum) {
        space = new UID((short) 0);
        this.objNum = 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

Method from java.rmi.server.ObjID Summary:
equals, hashCode, read, toString, write

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from java.rmi.server.ObjID Detail:
public boolean equals(Object obj) { if (obj instanceof ObjID) { ObjID id = (ObjID) obj; return objNum == id.objNum && space.equals(id.space); } else { return false; } } 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.
public int hashCode() { return (int) objNum; } Returns the hash code value for this object identifier, the object number.
public static ObjID read(ObjectInput in) throws IOException { long num = in.readLong(); UID space = UID.read(in); return new ObjID(num, space); } 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 ObjectInput#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.
public String toString() { return "[" + (space.equals(mySpace) ? "" : space + ", ") + objNum + "]"; } Returns a string representation of this object identifier.
public void write(ObjectOutput out) throws IOException { out.writeLong(objNum); space.write(out); } Marshals a binary representation of this `ObjID` to an `ObjectOutput` instance. Specifically, this method first invokes the given stream's ObjectOutput#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.

Method from java.rmi.server.ObjID Detail:

 public boolean equals(Object obj) {
        if (obj instanceof ObjID) {
            ObjID id = (ObjID) obj;
            return objNum == id.objNum && space.equals(id.space);
        } else {
            return false;
        }
}

ObjID

true

ObjID

 public int hashCode() {
        return (int) objNum;
}

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

 public static ObjID read(ObjectInput in) throws IOException {
        long num = in.readLong();
        UID space = UID.read(in);
        return new ObjID(num, space);
}

ObjID

ObjectInput

Specifically, this method first invokes the given stream's ObjectInput#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.

 public String toString() {
        return "[" + (space.equals(mySpace) ? "" : space + ", ") +
            objNum + "]";
}

Returns a string representation of this object identifier.

 public  void write(ObjectOutput out) throws IOException {
        out.writeLong(objNum);
        space.write(out);
}

ObjID

ObjectOutput

Specifically, this method first invokes the given stream's ObjectOutput#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.