com.google.appengine.api.labs.taskqueue
Interface Queue

public interface Queue

Queue is used to manage a task queue.

Implementations of this interface must be threadsafe.

Queues are transactional. If a datastore transaction is in progress when add() or add(TaskOptions) is invoked, the task will only be added to the queue if the datastore transaction successfully commits. If you want to add a task to a queue and have that operation succeed or fail independently of an existing datastore transaction you can invoke add(Transaction, TaskOptions) with a null transaction argument. Note that while the addition of the task to the queue can participate in an existing transaction, the execution of the task cannot participate in this transaction. In other words, when the transaction commits you are guaranteed that your task will run, not that your task executed successfully.

Field Summary

static java.lang.String	DEFAULT_QUEUE The default queue name.
static java.lang.String	DEFAULT_QUEUE_PATH The default queue path.

Method Summary

TaskHandle	add() Submits a task to this queue with an auto generated name with default options.
TaskHandle	add(TaskOptions taskOptions) Submits a task to this queue.
TaskHandle	add(Transaction txn, TaskOptions taskOptions) Submits a task to this queue in the provided Transaction.
java.lang.String	getQueueName() Returns the queue name.

Field Detail

DEFAULT_QUEUE

static final java.lang.String DEFAULT_QUEUE

The default queue name.

See Also:

Constant Field Values

DEFAULT_QUEUE_PATH

static final java.lang.String DEFAULT_QUEUE_PATH

The default queue path.

See Also:

Constant Field Values

Method Detail

getQueueName

java.lang.String getQueueName()

Returns the queue name.

add

TaskHandle add()

Submits a task to this queue with an auto generated name with default options.

This method is similar to calling add(TaskOptions) with a TaskOptions object returned by TaskOptions.Builder.withDefaults().

Returns:

A TaskHandle.

Throws:

InternalFailureException

java.lang.IllegalStateException - If the queue does not exist. (see queue.xml)

TaskAlreadyExistsException

TransientFailureException - Attempting the request after this exception may succeed.

UnsupportedTranslationException - If chosen character encoding is unsupported.

add

TaskHandle add(TaskOptions taskOptions)

Submits a task to this queue.

Parameters:

taskOptions - The definition of the task.

Returns:

A TaskHandle.

Throws:

InternalFailureException

java.lang.IllegalStateException - If the queue does not exist. (see queue.xml)

TaskAlreadyExistsException

TransientFailureException - Attempting the request after this exception may succeed.

UnsupportedTranslationException - If chosen character encoding is unsupported.

add

TaskHandle add(Transaction txn,
               TaskOptions taskOptions)

Submits a task to this queue in the provided Transaction. A task is added if and only if the transaction is applied successfully.

Parameters:

txn - an enclosing Transaction or null, if not null a task cannot be named.

taskOptions - The definition of the task.

Returns:

A TaskHandle.

Throws:

InternalFailureException

java.lang.IllegalStateException - If the queue does not exist. (see queue.xml)

TaskAlreadyExistsException

TransientFailureException - Attempting the request after this exception may succeed.

UnsupportedTranslationException - If chosen character encoding is unsupported.