VCLDequeueOperation

Interface FQN: it.greenvulcano.gvesb.virtual.DequeueOperation

Extends: it.greenvulcano.gvesb.virtual.Operation

/**
* This interface identifies operations used to perform dequeue.
*
* The DequeueOperation adds the acknowledge() method to the
* Operation interface in order to confirm consumed messages to the
* underlying MOM.
*
*/

Following the DequeueOperation constants

public static final String TYPE  = "dequeue";

/**
* Used in the setTimeout() in order to set an infinite
* timeout.
*/
public static final long   TO_INDEFINITELY = 0;

/**
* Used in the setTimeout() in order to set a non-blocking
* receive.
*/
public static final long   TO_NON_BLOCKING = -1;

Following the DequeueOperation public methods

/**
 * Execute the operation using an GVBuffer. Usually this method
 * is used in order to retrieve data from external systems.
 * Returns null if no messages are available or timeout occurs.
 * 
 * @param gvBuffer
 *        input data for the operation.
 *
 * @return an GVBuffer containing the operation result or null if 
 *         no messages are available or timeout occurs.
 * @exception ConnectionException
 *            if an error occurs making the connection to the external system.
 * @exception DequeueException
 *            if an error occurs performing the operation.
 * @exception InvalidDataException
 *            if the call fail because the data are invalid. GreenVulcano ESB 
 *            should not retry to perform the operation with the same data.
 */
public GVBuffer perform(GVBuffer gvBuffer) throws ConnectionException, DequeueException, InvalidDataException;

/**
* This method acknowledges the message identified by the given Id.
*
* @param id
* @throws ConnectionException
* @throws AcknowledgeException
*/
public void acknowledge(Id id) throws ConnectionException, AcknowledgeException;

/**
* This method acknowledges all the messages.
*
* @throws ConnectionException
* @throws AcknowledgeException
*/
public void acknowledgeAll() throws ConnectionException, AcknowledgeException;

/**
* This method roll-back the dequeue of the message identified by the given
* Id.
*
* @param id
* @throws ConnectionException
* @throws AcknowledgeException
*/
public void rollback(Id id) throws ConnectionException, AcknowledgeException;

/**
* This method roll-back the dequeue of all the messages.
*
* @throws ConnectionException
* @throws AcknowledgeException
*/
public void rollbackAll() throws ConnectionException, AcknowledgeException;

/**
* This method sets the filter for messages to receive. 
* This filter is valid only for the first perform() invocation.
* The filter is reset also if perform() terminates with an exception. 
* Despite the GVVCL is a virtual interface, the syntax for the filter is
* like the syntax for JMS selectors. The concrete implementation must
* adapt to the underlying MOM.
*
* @param filter
* @throws FilterException
*/
public void setFilter(String filter) throws FilterException;

/**
* This method sets the timeout for the receive operation. 
* If 0 then the receive blocks indefinitely. If > 0
* then this parameter specify, in milliseconds, the time that the
* receive must wait for a message. If < 0 then executes a
* non-blocking receive. 
* This parameter is valid only for the first perform() invocation.
* The timeout is reset also if perform() terminate with an exception.
*
* @param timeout
*        Specifies the receive timeout. If > 0 specifies the
*        milliseconds for timeout. It is possible to use the
*        TO_xxx constants in order to specify a non-blocking
*        receive operation or a indefinitely blocking receive.
*
*/
public void setTimeout(long timeout);