org.apache.jackrabbit.mongomk.api.command

Interface Command<T>

Type Parameters:

T - The result type of the Command.

All Known Implementing Classes:

BaseCommand, CommitCommand, CommitCommandNew, DiffCommand, GetBlobLengthCommandGridFS, GetHeadRevisionCommand, GetJournalCommand, GetNodesCommand, GetNodesCommandNew, GetRevisionHistoryCommand, MergeCommand, NodeExistsCommand, OneLevelDiffCommand, ReadBlobCommandGridFS, WaitForCommitCommand, WriteBlobCommandGridFS

public interface Command<T>

The Command framework provides an way to encapsulate specific actions of the {code MicroKernel}.

It adds some functionality for retries and other non business logic related actions (i.e. logging, performance tracking, etc).

See Also:

Command Pattern, CommandExecutor

Method Summary

Methods

Modifier and Type	Method and Description
T	execute() Executes the Command and returns its result.
int	getNumOfRetries() Returns the number of retries this Command should be retried in case of an error or false result.
boolean	needsRetry(Exception e) Will be called in case of an Exception during the execution and a given number of retries which has not exceeded.
boolean	needsRetry(T result) Will be called in case of a successful execution and a given number of retries which has not exceeded.

Method Detail

execute

T execute()
          throws Exception

Executes the Command and returns its result.

Returns:

The result.

Throws:

Exception - If an error occurred while executing.

getNumOfRetries

int getNumOfRetries()

Returns the number of retries this Command should be retried in case of an error or false result.

The number of reties is evaluated in the following way:

n < 0: Unlimited retries n = 0: No retries (just one execution) n > 0: Corresponding number of retries

In order to determine whether the Command should be retired on needsRetry(Exception) or needsRetry(Object) will be called.

Returns:

The number of retries.

See Also:

needsRetry(Exception), needsRetry(Object)

needsRetry

boolean needsRetry(Exception e)

Will be called in case of an Exception during the execution and a given number of retries which has not exceeded.

Parameters:

e - The Exception which was thrown.

Returns:

true if a retry should be performed, else false.

needsRetry

boolean needsRetry(T result)

Will be called in case of a successful execution and a given number of retries which has not exceeded.

This gives the implementor a chance to retry a false result.

Parameters:

result - The result of the execution.

Returns:

true if a retry should be performed, else false.