org.jgroups

Class View

java.lang.Object

org.jgroups.View

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, java.lang.Cloneable, Streamable

Direct Known Subclasses:

MergeView

public class View
extends java.lang.Object
implements java.io.Externalizable, java.lang.Cloneable, Streamable

A view is a local representation of the current membership of a group. Only one view is installed in a channel at a time. Views contain the address of its creator, an ID and a list of member addresses. These adresses are ordered, and the first address is always the coordinator of the view. This way, each member of the group knows who the new coordinator will be if the current one crashes or leaves the group. The views are sent between members using the VIEW_CHANGE event

Version:

$Id: View.java,v 1.18 2007/10/01 07:24:41 belaban Exp $

Author:

Bela Ban

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Vector<Address>	members A list containing all the members of the view This list is always ordered, with the coordinator being the first member.
protected java.util.Map<java.lang.String,java.lang.Object>	payload
protected ViewId	vid

Constructor Summary

Constructors

Constructor and Description
View() creates an empty view, should not be used
View(Address creator, long id, java.util.Vector<Address> members) Creates a new view
View(ViewId vid, java.util.Vector<Address> members) Creates a new view

Method Summary

Methods

Modifier and Type	Method and Description
void	addPayload(java.lang.String key, java.lang.Object value) Adds a key and value to the view.
java.lang.Object	clone() creates a copy of this view
boolean	containsMember(Address mbr) returns true, if this view contains a certain member
boolean	equals(java.lang.Object obj)
Address	getCreator() returns the creator of this view if this view was created with the empty constructur, null will be returned
java.util.Vector<Address>	getMembers() Returns a reference to the List of members (ordered) Do NOT change this list, hence your will invalidate the view Make a copy if you have to modify it.
java.lang.Object	getPayload(java.lang.String key)
ViewId	getVid() returns the view ID of this view if this view was created with the empty constructur, null will be returned
int	hashCode()
java.lang.String	printDetails() debug only
void	readExternal(java.io.ObjectInput in)
void	readFrom(java.io.DataInputStream in) Read the state of the current object (including superclasses) from instream Note that the input stream must not be closed
int	serializedSize()
int	size() returns the number of members in this view
java.lang.String	toString()
void	writeExternal(java.io.ObjectOutput out)
void	writeTo(java.io.DataOutputStream out) Write the entire state of the current object (including superclasses) to outstream.

Methods inherited from class java.lang.Object

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

Field Detail

vid

protected ViewId vid

members

protected java.util.Vector<Address> members

A list containing all the members of the view This list is always ordered, with the coordinator being the first member. the second member will be the new coordinator if the current one disappears or leaves the group.

payload

protected java.util.Map<java.lang.String,java.lang.Object> payload

Constructor Detail

View

public View()

creates an empty view, should not be used

View

public View(ViewId vid,
    java.util.Vector<Address> members)

Creates a new view

Parameters:

vid - The view id of this view (can not be null)

members - Contains a list of all the members in the view, can be empty but not null.

View

public View(Address creator,
    long id,
    java.util.Vector<Address> members)

Creates a new view

Parameters:

creator - The creator of this view (can not be null)

id - The lamport timestamp of this view

members - Contains a list of all the members in the view, can be empty but not null.

Method Detail

getVid

public ViewId getVid()

returns the view ID of this view if this view was created with the empty constructur, null will be returned

Returns:

the view ID of this view

getCreator

public Address getCreator()

returns the creator of this view if this view was created with the empty constructur, null will be returned

Returns:

the creator of this view in form of an Address object

getMembers

public java.util.Vector<Address> getMembers()

Returns a reference to the List of members (ordered) Do NOT change this list, hence your will invalidate the view Make a copy if you have to modify it.

Returns:

a reference to the ordered list of members in this view

containsMember

public boolean containsMember(Address mbr)

returns true, if this view contains a certain member

Parameters:

mbr - - the address of the member,

Returns:

true if this view contains the member, false if it doesn't if the argument mbr is null, this operation returns false

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

size

public int size()

returns the number of members in this view

Returns:

the number of members in this view 0..n

clone

public java.lang.Object clone()

creates a copy of this view

Overrides:

clone in class java.lang.Object

Returns:

a copy of this view

printDetails

public java.lang.String printDetails()

debug only

addPayload

public void addPayload(java.lang.String key,
              java.lang.Object value)

Adds a key and value to the view. Since the payloads will be shipped around *with* the view, so the keys and values need to be serializable. Note that the total serialized size of all keys and values cannot exceed 65000 bytes !

Parameters:

key -

value -

getPayload

public java.lang.Object getPayload(java.lang.String key)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Specified by:

writeExternal in interface java.io.Externalizable

Throws:

java.io.IOException

readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Specified by:

readExternal in interface java.io.Externalizable

Throws:

java.io.IOException

java.lang.ClassNotFoundException

writeTo

public void writeTo(java.io.DataOutputStream out)
             throws java.io.IOException

Description copied from interface: Streamable

Write the entire state of the current object (including superclasses) to outstream. Note that the output stream must not be closed

Specified by:

writeTo in interface Streamable

Throws:

java.io.IOException

readFrom

public void readFrom(java.io.DataInputStream in)
              throws java.io.IOException,
                     java.lang.IllegalAccessException,
                     java.lang.InstantiationException

Description copied from interface: Streamable

Read the state of the current object (including superclasses) from instream Note that the input stream must not be closed

Specified by:

readFrom in interface Streamable

Throws:

java.io.IOException

java.lang.IllegalAccessException

java.lang.InstantiationException

serializedSize

public int serializedSize()