org.space4j
Interface Space4J

All Known Implementing Classes:

MasterSpace4J, SimpleSpace4J, SlaveSpace4J

public interface Space4J

Our Java database of objects. Clients will use the Space4J object to execute commands in the underlying space. Space4J will be running in the same JVM the client is running, in other words, the client will be able to access the Space4J directly in memomy.

Method Summary

int	exec(Command cmd) Executes a command on the underlying Space.
void	executeSnapshot() Take a snapshot of the Space to disk.
Space	getSpace() Returns the Space where the Objects are stored, so the client can direct access them.
int	reapply(Command cmd) Re-apply a command on the underlying Space.
void	start() Starts the Space4J.

Method Detail

reapply

int reapply(Command cmd)
            throws CommandException,
                   LoggerException

Re-apply a command on the underlying Space. This method will be used to re-apply the commands from the logs. OBS: Logging is done AFTER the command is executed. If, for some reason, a CommandException is thrown, the command will not be logged.

Parameters:

cmd - The command to execute.

Returns:

An int containing the number of objects modified by this operation.

Throws:

CommandException - if there is a problem executing this command

LoggerException - if there is a problem logging thie command

exec

int exec(Command cmd)
         throws CommandException,
                LoggerException

Executes a command on the underlying Space. The client must use this method to perform any update on the Space. The client must never do any modifications on the Space objects without using this method, otherwise, the change will not be persisted. Space4J will execute the command and log the changes for future recovery if needed. OBS: Logging is done AFTER the command is executed. If, for some reason, a CommandException is thrown, the command will not be logged.

Parameters:

cmd - The command to execute.

Returns:

An int containing the number of objects modified by this operation.

Throws:

CommandException - if there is a problem executing this command

LoggerException - if there is a problem logging thie command

executeSnapshot

void executeSnapshot()
                     throws LoggerException

Take a snapshot of the Space to disk. The Space will be serialized and written to disk.

Throws:

LoggerException

getSpace

Space getSpace()

Returns the Space where the Objects are stored, so the client can direct access them.

Returns:

a Space if Space4J is running locally or null otherwise

start

void start()
           throws java.net.UnknownHostException,
                  java.io.IOException,
                  java.lang.ClassNotFoundException

Starts the Space4J. This is only necessary for a replicated Space4J.

Throws:

java.net.UnknownHostException

java.io.IOException

java.lang.ClassNotFoundException