com.atomikos.icatch.msg
Class MessageParticipant

java.lang.Object
  com.atomikos.icatch.msg.MessageParticipant

All Implemented Interfaces:

Participant, Externalizable, Serializable

public class MessageParticipant
extends Object
implements Participant, Externalizable

A participant implementation that can be used on a message-based platform. This participant acts as a core proxy for remote participants that co-operate over a message-based 2PC protocol. By introducing the abstract message interface framework, the same participant instance can be reused for different message systems and different protocols.

See Also:

Serialized Form

Field Summary

Fields inherited from interface com.atomikos.icatch.Participant

READ_ONLY

Constructor Summary

MessageParticipant()

MessageParticipant(String remoteUri, Object address, Transport transport, HeuristicMessage[] msgs, boolean earlyPrepared, boolean readOnly)

Method Summary

HeuristicMessage[]	commit(boolean onePhase) Commits the participant's work.
boolean	equals(Object o)
void	forget() Indicates that a heuristic participant can forget about its work.
Object	getAddress()
int	getCommitProtocol() Getter for the commit protocol.
int	getFormat() Getter for the format.
HeuristicMessage[]	getHeuristicMessages()
int	getTransportProtocol() Getter for the transport protocol.
String	getURI()
int	hashCode()
int	prepare() Prepares the participant.
void	readExternal(ObjectInput in)
boolean	recover() Called by the transaction manager (TM) at recovery time, and this should reconstruct the internal state.
HeuristicMessage[]	rollback() Rollback of the participant's work.
void	setCascadeList(Dictionary allParticipants) For cascading 2PC, this method sets the information needed to cascade.
void	setGlobalSiblingCount(int count) Set by the root coordinator: the total no of siblings detected.
String	toString() Returns a string representation of this participant proxy.
void	writeExternal(ObjectOutput out)

Methods inherited from class java.lang.Object

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

Constructor Detail

MessageParticipant

public MessageParticipant()

MessageParticipant

public MessageParticipant(String remoteUri,
                          Object address,
                          Transport transport,
                          HeuristicMessage[] msgs,
                          boolean earlyPrepared,
                          boolean readOnly)

Method Detail

getTransportProtocol

public int getTransportProtocol()

Getter for the transport protocol.

getCommitProtocol

public int getCommitProtocol()

Getter for the commit protocol.

getFormat

public int getFormat()

Getter for the format.

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

Specified by:

readExternal in interface Externalizable

Throws:

IOException

ClassNotFoundException

recover

public boolean recover()
                throws SysException

Description copied from interface: Participant

Called by the transaction manager (TM) at recovery time, and this should reconstruct the internal state.

Specified by:

recover in interface Participant

Returns:

boolean False if the instance could not be recovered. It is up to the transaction manager to determine the severity of this case.

Throws:

SysException

See Also:

Participant

getAddress

public Object getAddress()

getURI

public String getURI()

Specified by:

getURI in interface Participant

Returns:

String The unique URI for this remote participant, or null for local instances.

See Also:

Participant

setCascadeList

public void setCascadeList(Dictionary allParticipants)
                    throws SysException

Description copied from interface: Participant

For cascading 2PC, this method sets the information needed to cascade. This method is relevant only for transaction monitors; leave empty otherwise!

Specified by:

setCascadeList in interface Participant

Parameters:

allParticipants - The information needed by the transaction monitor.

Throws:

SysException

See Also:

Participant.

setGlobalSiblingCount

public void setGlobalSiblingCount(int count)

Description copied from interface: Participant

Set by the root coordinator: the total no of siblings detected. This method is relevant only for transaction monitors; leave empty otherwise!

Specified by:

setGlobalSiblingCount in interface Participant

Parameters:

count - The global count.

See Also:

Participant.

getHeuristicMessages

public HeuristicMessage[] getHeuristicMessages()

Specified by:

getHeuristicMessages in interface Participant

Returns:

HeuristicMessage[] An array of heuristic messages, or null if none.

See Also:

Participant

hashCode

public int hashCode()

Overrides:

hashCode in class Object

See Also:

Participant.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

toString

public String toString()

Returns a string representation of this participant proxy.

Overrides:

toString in class Object

prepare

public int prepare()
            throws RollbackException,
                   HeurHazardException,
                   HeurMixedException,
                   SysException

Description copied from interface: Participant

Prepares the participant. Any locks for this participant's work should be recoverable (either saved to an external file OR be part of the instance's non-transient state so that they can be flushed into the transaction manager's log).

Specified by:

prepare in interface Participant

Returns:

int READ_ONLY if no second round is needed. Participants that return this value on prepare will not be called by commit or rollback afterwards.

Throws:

RollbackException - For a NO vote. This indicates that the participant has already rolled back (or marked for rollback) the work on behalf of this participant.

HeurHazardException - On possible conflicts. This happens for remote participants instances, in case of communication failures.

HeurMixedException - If some subordinate participants voted YES, timed out and committed heuristically whereas afterwards some NO votes where received.

SysException

See Also:

Participant

commit

public HeuristicMessage[] commit(boolean onePhase)
                          throws HeurRollbackException,
                                 HeurHazardException,
                                 HeurMixedException,
                                 RollbackException,
                                 SysException

Description copied from interface: Participant

Commits the participant's work. NOTE: custom participant implementations should preferably be made for the server's local VM (e.g., it is better not to do this over RMI). Also, they should rely on the transaction manager for heuristic timeout (and NOT decide to terminate heuristically themselves). In that case, implementations never need to throw any of the heuristic exceptions of this method.

Specified by:

commit in interface Participant

Parameters:

onePhase - If true, one-phase commit is being started. If the participant has received a prepare call earlier, then it should throw a SysException here.

Returns:

HeuristicMessage[] An array of messages, null if none.

Throws:

HeurHazardException - On possible conflicts.

RollbackException - In case of one-phase commit, and the transaction has been rolled back at the time commit is called.

SysException

HeurRollbackException

HeurMixedException

See Also:

Participant

rollback

public HeuristicMessage[] rollback()
                            throws HeurCommitException,
                                   HeurMixedException,
                                   HeurHazardException,
                                   SysException

Description copied from interface: Participant

Rollback of the participant's work. NOTE: custom participant implementations should preferably be made for the server's local VM (e.g., it is better not to do this over RMI). Also, they should rely on the icatch transaction manager for heuristic timeout (and NOT decide to terminate heuristically themselves). In that case, implementations never need to throw any of the heuristic exceptions of this method.

Specified by:

rollback in interface Participant

Returns:

HeuristicMessage[] An array of messages, null if none.

Throws:

HeurCommitException - If the participant committed.

HeurMixedException - If part of the work was rolled back.

HeurHazardException - If the participant's final state is unsure.

SysException

See Also:

Participant

forget

public void forget()

Description copied from interface: Participant

Indicates that a heuristic participant can forget about its work. If implementations rely on the transaction manager to decide when to do heuristics (rather then deciding in the participant implementation), then leave this method empty.

Specified by:

forget in interface Participant

See Also:

Participant