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Oracle® C++ Call Interface Programmer's Guide
10g Release 2 (10.2)

B14294-02
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Consumer Class

The Consumer class supports dequeuing of Messages and controls the dequeuing options.

Table 12-14 Enumerated Values Used by Consumer Class

Attribute Options
DequeMode
  • DEQ_BROWSE indicates that the message should be read without acquiring a lock; equivalent to a SELECT.

  • DEQ_LOCKED indicates that the message should be read. Get its write lock, which lasts s for the duration of the transaction; equivalent to a SELECT FOR UPDATE.

  • DEQ_REMOVE indicates that the message should be read. Update or delete it; the message can be retained in the queue table based on the retention properties. This is the default setting.

  • DEQ_REMOVE_NODATA indicates that the receipt of the message should be confirmed, but its actual content should not be delivered.

Navigation
  • DEQ_FIRST_MSG indicates that the first available message on the queue that matches the search criteria must be retrieved. Resets the position to the beginning of the queue.

  • DEQ_NEXT_TRANSACTION indicates that the next available message on the queue that matches the search criteria must be retrieved. If the previous message belongs to a message group, AQ will retrieve the next available message that matches the search criteria and belongs to the message group. This is the default setting.

  • DEQ_NEXT_MSG indicates that the remainder of the current transaction group, if any, should be skipped. The first message of the next transaction group will then be retrieved. This option can only be used if message grouping is enabled for the current queue.

Visibility
  • DEQ_IMMEDIATE indicates that the dequeued message is not part of the current transaction. It constitutes a transaction on its own.

  • DEQ_ON_COMMIT indicates that the dequeue will be part of the current transaction. This is the default setting.

DequeWaitOption
  • DEQ_WAIT_FOREVER indicates that the consumer will wait for the Message indefinitely.

  • DEQ_NO_WAIT indicates that there should be not wait if there are no messages on the queue.


Table 12-15 Summary of Consumer Methods

Method Description

Consumer()

Consumer class constructor.

getConsumerName()

Retrieves the name of the Consumer.

getCorrelationId()

Retrieves she correlation id of the message that is to be dequeued.

getDequeueMode()

Retrieves the dequeue mode of the Consumer.

getMessageIdToDequeue()

Retrieves the id of the message that will be dequeued.

getQueueName()

Gets the name of the queue used by the consumer.

getPositionOfMessage()

Retrieves the position of the Message that will be dequeued.

getTransformation()

Retrieves the transformation applied before a Message is dequeued.

getVisibility()

Retrieves the transactional behavior of the dequeue operation.

getWaitTime()

Retrieves the specified behavior of the Consumer when waiting for a Message with matching search criteria.

isNull()

Tests whether the Consumer object is NULL.

operator=()

Assignment operator for the Consumer class..

receive()

Receives and dequeues a Message

setAgent()

Sets the Agent's name and address (queue name) on the consumer.

setConsumerName()

Sets the Consumer name.

setCorrelationId()

Specifies the correlation identifier of the message to be dequeued.

setDequeueMode()

Specifies the locking behavior associated with dequeuing.

setMessageIdToDequeue()

Specifies the identifier of the Message to be dequeued.

setNull()

Nullifies the Consumer; frees the memory associated with this object.

setPositionOfMessage()

Specifies position of the Message to be retrieved.

setQueueName()

Specifies the name of a queue prior to dequeuing Messages.

setTransformation()

Specifies transformation applied before dequeuing a Message.

setVisibility()

Specifies if Message should be dequeued as part of the current transaction.

setWaitTime()

Specifies wait conditions if there are no Messages with matching criteria.



Consumer()

Consumer class constructor.

Syntax Description
Consumer(
   const Connection *conn);
Creates a new Consumer object with the specified Connection handle.
Consumer(
   const Connection *conn
   const Agent& agent);
Creates a new Consumer object with specified Connection and properties of the specified Agent.
Consumer(
   const Connection *conn,
   const string& queue);
Creates a new Consumer object with specified Connection and queue.
Consumer(
   const Consumer& consumer);
Copy constructor.

Parameter Description
conn
The connection in which the Consumer is created.
agent
Agent assigned to the Consumer.
queue
Queue at which the Consumer retrieves messages.
consumer
Original Consumer object.


getConsumerName()

Retrieves the name of the Consumer.

Syntax

string getConsumerName() const;


getCorrelationId()

Retrieves she correlation id of the message that is to be dequeued

Syntax

string geCorrelationId() const;


getDequeueMode()

Retrieves the dequeue mode of the Consumer. DequeueMode is defined in Table 12-14.

Syntax

DequeueMode getDequeueMode() const;


getMessageIdToDequeue()

Retrieves the id of the message that will be dequeued.

Syntax

Bytes getMessageToDequeue() const;


getPositionOfMessage()

Retrieves the position, or navigation, of the message that will be dequeued. Navigation is defined in Table 12-14.

Syntax

Navigation getPositionOfMessage() const;


getQueueName()

Gets the name of the queue used by the consumer.

Syntax

string getQueueName() const;


getTransformation()

Retrieves the transformation applied before a Message is dequeued.

Syntax

string getTransformation() const;


getVisibility()

Retrieves the transactional behavior of the dequeue operation, or visibility. Visibility is defined in Table 12-14.

Syntax

Visibility getVisibility() const;


getWaitTime()

Retrieves the specified behavior of the Consumer when waiting for a Message with matching search criteria. DequeWaitOption is defined in Table 12-14.

Syntax

DequeWaitOption getWaitTime() const;


isNull()

Tests whether the Consumer object is NULL. If the Consumer object is NULL, TRUE is returned; otherwise, FALSE is returned.

Syntax

bool isNull() const;


operator=()

Assignment operator for Consumer class.

Syntax

void operator=(
   const Consumer& consumer); 

Parameter Description
consumer
The original Consumer.


receive()

Receives and dequeues a Message.

Syntax

Message receive(
   Message::PayloadType pType,
   const string& type="",
   const string& schema="");
Parameter Description
pType
The type of payload expected. Payload Type is defined in Table 12-14.
type
The type of the payload when pType is OBJECT.
schema
The schema in which the type is defined when pType is OBJECT.


setAgent()

Sets the Agent's name and address (queue name) on the consumer.

Syntax

void setAgent(
   const Agent& agent);
Parameter Description
agent
Name of the Agent.


setConsumerName()

Sets the Consumer name. Only messages with matching consumer name can be accessed. If a queue is not set up for multiple consumer, this option should be set to NULL.

Syntax

void setConsumerName(
   const string& name);

Parameter Description
name
Name of the Consumer.


setCorrelationId()

Specifies the correlation identifier of the message to be dequeued. Special pattern matching characters, such as the percent sign (%) and the underscore(_) can be used. If several messages satisfy the pattern, the order of dequeuing is undetermined.

Syntax

void setCorrelationId
   const string& id);

Parameter Description
id
The identifier of the Message.


setDequeueMode()

Specifies the locking behavior associated with dequeuing.

Syntax

void setDequeueMode(
   DequeueMode mode);

Parameter Description
mode
Behavior of enqueuing. DequeMode is defined in Table 12-14.


setMessageIdToDequeue()

Specifies the identifier of the Message to be dequeued.

Syntax

void setMessageIdToDequeue(
   const Bytes& msgid);
Parameter Description
msgid
Identifier of the Message to be dequeued.


setNull()

Nullifies the Consumer; frees the memory associated with this object.

Syntax

void setNull();


setPositionOfMessage()

Specifies position of the Message to be retrieved.

Syntax

void setPositionOfMessage(
   Navigation pos);

Parameter Description
pos
Position of the message, Navigation, is defined in Table 12-14.


setQueueName()

Specifies the name of a queue prior to dequeuing Messages. Typically used when dequeuing multiple messages from the same queue.

Syntax

void setQueueName(
   const string& queue);

Parameter Description
queue
The name of a valid queue in the database.


setTransformation()

Specifies transformation applied before dequeuing the Message.

Syntax

void setTransformation(
   string &fName);
Parameter Description
fName
SQL transformation function.


setVisibility()

Specifies if Message should be dequeued as part of the current transaction. Visibility parameter is ignored when in DEQ_BROWSE mode.

Syntax

void setVisibility(
   Visibility option);
Parameter Description
option
Visibility option being set, defined in Table 12-14.


setWaitTime()

Specifies wait conditions if there are no Messages with matching criteria. The wait parameter is ignored if messages in the same group are being dequeued.

Syntax

void setWaitTime(
   DequeWaitOption wait);

Parameter Description
wait
Waiting conditions. DequeWaitOption is defined in Table 12-14.