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java.lang.Objectorg.javagroups.stack.Protocol
org.javagroups.protocols.STATE_TRANSFER
State transfer layer. Upon receiving a GET_STATE event from JChannel, a MAKE_COPY message is sent to all members. When the originator receives MAKE_COPY, it queues all messages to the channel. When another member receives the message, it asks the JChannel to provide it with a copy of the current state (GetStateEvent is received by application, returnState() sends state down the stack). Then the current layer sends a unicast RETURN_STATE message to the coordinator, which returns the cached copy. When the state is received by the originator, the GET_STATE sender is unblocked with a GET_STATE_OK event up the stack (unless it already timed out).
Requires QUEUE layer on top.
Field Summary |
Fields inherited from class org.javagroups.stack.Protocol |
down_handler, down_prot, down_queue, down_thread, down_thread_prio, observer, props, stack, up_handler, up_prot, up_queue, up_thread, up_thread_prio |
Constructor Summary | |
STATE_TRANSFER()
|
Method Summary | |
void |
down(Event evt)
An event is to be sent down the stack. |
java.lang.String |
getName()
All protocol names have to be unique ! |
java.lang.Object |
handle(Message msg)
|
void |
init()
Called after instance has been created (null constructor) and before protocol is started. |
java.util.Vector |
requiredUpServices()
List of events that are required to be answered by some layer above. |
boolean |
setProperties(java.util.Properties props)
Configures the protocol initially. |
void |
start()
This method is called on a Channel.connect(String) . |
void |
stop()
This method is called on a Channel.disconnect() . |
void |
up(Event evt)
An event was received from the layer below. |
Methods inherited from class org.javagroups.stack.Protocol |
destroy, getDownProtocol, getDownQueue, getProperties, getUpProtocol, getUpQueue, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setUpProtocol, startDownHandler, startUpHandler, stopInternal |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public STATE_TRANSFER()
Method Detail |
public java.lang.String getName()
getName
in class Protocol
public void init() throws java.lang.Exception
Protocol
init
in class Protocol
java.lang.Exception
- Thrown if protocol cannot be initialized successfully. This will cause the
ProtocolStack to fail, so the channel constructor will throw an exceptionpublic void start() throws java.lang.Exception
Protocol
Channel.connect(String)
. Starts work.
Protocols are connected and queues are ready to receive events.
Will be called from bottom to top. This call will replace
the START and START_OK events.
start
in class Protocol
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack
to fail, so Channel.connect(String)
will throw an exceptionpublic void stop()
Protocol
Channel.disconnect()
. Stops work (e.g. by closing multicast socket).
Will be called from top to bottom. This means that at the time of the method invocation the
neighbor protocol below is still working. This method will replace the
STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that
when this method is called all messages in the down queue will have been flushed
stop
in class Protocol
public boolean setProperties(java.util.Properties props)
Protocol
"loopback=false;unicast_inport=4444"
setProperties
in class Protocol
public java.util.Vector requiredUpServices()
Protocol
requiredUpServices
in class Protocol
public void up(Event evt)
Protocol
passDown()
or c) the event (or another event) is sent up
the stack using passUp()
.
up
in class Protocol
public void down(Event evt)
Protocol
passDown()
. In case of a GET_ADDRESS event (which tries to
retrieve the stack's address from one of the bottom layers), the layer may need to send
a new response event back up the stack using passUp()
.
down
in class Protocol
public java.lang.Object handle(Message msg)
handle
in interface RequestHandler
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