no.nordicsemi.android.ble

Class Request

java.lang.Object

no.nordicsemi.android.ble.Request

Direct Known Subclasses:

RequestQueue, SimpleRequest, TimeoutableRequest

public abstract class Request
extends java.lang.Object

On Android, when multiple BLE operations needs to be done, it is required to wait for a proper BluetoothGattCallback callback before calling another operation. In order to make BLE operations easier the BleManager allows to enqueue a request containing all data necessary for a given operation. Requests are performed one after another until the queue is empty.

Field Summary

Fields

Modifier and Type	Field and Description
protected no.nordicsemi.android.ble.CallbackHandler	handler
protected no.nordicsemi.android.ble.RequestHandler	requestHandler

Method Summary

Modifier and Type	Method and Description
Request	before(BeforeCallback callback) Sets a callback that will be executed before the execution of this operation starts.
static SimpleRequest	createBond() Deprecated. Access to this method will change to package-only. Use BleManager.createBond() instead.
Request	done(SuccessCallback callback) Use to set a completion callback.
void	enqueue() Enqueues the request for asynchronous execution.
Request	fail(FailCallback callback) Use to set a callback that will be called in case the request has failed.
Request	invalid(InvalidRequestCallback callback) Use to set a callback that will be called in case the request was invalid, for example called before the device was connected.
static ConnectionPriorityRequest	newConnectionPriorityRequest(int priority) Deprecated. Access to this method will change to package-only. Use BleManager.requestConnectionPriority(int) instead.
static WriteRequest	newDisableBatteryLevelNotificationsRequest() Deprecated. Use newDisableNotificationsRequest(BluetoothGattCharacteristic) instead.
static WriteRequest	newDisableIndicationsRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.disableNotifications(BluetoothGattCharacteristic) instead.
static WriteRequest	newDisableNotificationsRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.disableNotifications(BluetoothGattCharacteristic) instead.
static WriteRequest	newEnableBatteryLevelNotificationsRequest() Deprecated. Use newEnableNotificationsRequest(BluetoothGattCharacteristic) with BatteryLevelDataCallback from Android BLE Common Library instead.
static WriteRequest	newEnableIndicationsRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.enableIndications(BluetoothGattCharacteristic) instead.
static WriteRequest	newEnableNotificationsRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.enableNotifications(BluetoothGattCharacteristic) instead.
static MtuRequest	newMtuRequest(int mtu) Deprecated. Access to this method will change to package-only. Use BleManager.requestMtu(int) instead.
static ReadRequest	newReadBatteryLevelRequest() Deprecated. Use newReadRequest(BluetoothGattCharacteristic) with BatteryLevelDataCallback from Android BLE Common Library instead.
static PhyRequest	newReadPhyRequest() Deprecated. Access to this method will change to package-only. Use BleManager.readPhy() instead.
static ReadRequest	newReadRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.readCharacteristic(BluetoothGattCharacteristic) instead.
static ReadRequest	newReadRequest(android.bluetooth.BluetoothGattDescriptor descriptor) Deprecated. Access to this method will change to package-only. Use BleManager.readDescriptor(BluetoothGattDescriptor) instead.
static ReadRssiRequest	newReadRssiRequest() Deprecated. Access to this method will change to package-only. Use BleManager.readRssi() instead.
static SimpleRequest	newRefreshCacheRequest() Deprecated. Access to this method will change to package-only. Use BleManager.refreshDeviceCache() instead.
static PhyRequest	newSetPreferredPhyRequest(int txPhy, int rxPhy, int phyOptions) Deprecated. Access to this method will change to package-only. Use BleManager.setPreferredPhy(int, int, int) instead.
static SleepRequest	newSleepRequest(long delay) Deprecated. Access to this method will change to package-only. Use BleManager.sleep(long) instead.
static WaitForValueChangedRequest	newWaitForIndicationRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.waitForIndication(BluetoothGattCharacteristic) instead.
static WaitForValueChangedRequest	newWaitForNotificationRequest(android.bluetooth.BluetoothGattCharacteristic characteristic) Deprecated. Access to this method will change to package-only. Use BleManager.waitForNotification(BluetoothGattCharacteristic) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattCharacteristic characteristic, byte[] value) Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[]) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattCharacteristic characteristic, byte[] value, int writeType) Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, Data) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattCharacteristic characteristic, byte[] value, int offset, int length) Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[], int, int) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattCharacteristic characteristic, byte[] value, int offset, int length, int writeType) Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[], int, int) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattDescriptor descriptor, byte[] value) Deprecated. Access to this method will change to package-only. Use BleManager.writeDescriptor(BluetoothGattDescriptor, byte[]) instead.
static WriteRequest	newWriteRequest(android.bluetooth.BluetoothGattDescriptor descriptor, byte[] value, int offset, int length) Deprecated. Access to this method will change to package-only. Use BleManager.writeDescriptor(BluetoothGattDescriptor, byte[], int, int) instead.
static SimpleRequest	removeBond() Deprecated. Access to this method will change to package-only. Use BleManager.removeBond() instead.
Request	setHandler(android.os.Handler handler) Sets the handler that will be used to invoke callbacks.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

requestHandler

protected no.nordicsemi.android.ble.RequestHandler requestHandler

handler

protected no.nordicsemi.android.ble.CallbackHandler handler

Method Detail

setHandler

@NonNull
public Request setHandler(@NonNull
                                    android.os.Handler handler)

Sets the handler that will be used to invoke callbacks. By default, the handler set in BleManager will be used.

Parameters:

handler - The handler to invoke callbacks for this request.

Returns:

The request.

createBond

@Deprecated
 @NonNull
public static SimpleRequest createBond()

Deprecated. Access to this method will change to package-only. Use BleManager.createBond() instead.

Creates a new request that will start pairing with the device.

Returns:

The new request.

removeBond

@Deprecated
 @NonNull
public static SimpleRequest removeBond()

Deprecated. Access to this method will change to package-only. Use BleManager.removeBond() instead.

Creates a new request that will remove the bonding information from the Android device. This is done using reflections and may not work on all devices.

The device will disconnect after calling this method. The success callback will be called after the device got disconnected, when the BluetoothDevice.getBondState() changes to BluetoothDevice.BOND_NONE.

Returns:

The new request.

newReadRequest

@Deprecated
 @NonNull
public static ReadRequest newReadRequest(@Nullable
                                                                 android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.readCharacteristic(BluetoothGattCharacteristic) instead.

Creates new Read Characteristic request. The request will not be executed if given characteristic is null or does not have READ property. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to be read.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattCharacteristic characteristic,
                                                                   @Nullable
                                                                   byte[] value)

Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[]) instead.

Creates new Write Characteristic request. The request will not be executed if given characteristic is null or does not have WRITE property. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattCharacteristic characteristic,
                                                                   @Nullable
                                                                   byte[] value,
                                                                   int writeType)

Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, Data) instead.

Creates new Write Characteristic request. The request will not be executed if given characteristic is null or does not have WRITE property. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

writeType - write type to be used, one of BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT, BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattCharacteristic characteristic,
                                                                   @Nullable
                                                                   byte[] value,
                                                                   int offset,
                                                                   int length)

Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[], int, int) instead.

Creates new Write Characteristic request. The request will not be executed if given characteristic is null or does not have WRITE property. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

offset - the offset from which value has to be copied.

length - number of bytes to be copied from the value buffer.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattCharacteristic characteristic,
                                                                   @Nullable
                                                                   byte[] value,
                                                                   int offset,
                                                                   int length,
                                                                   int writeType)

Deprecated. Access to this method will change to package-only. Use BleManager.writeCharacteristic(BluetoothGattCharacteristic, byte[], int, int) instead.

Creates new Write Characteristic request. The request will not be executed if given characteristic is null or does not have WRITE property. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

offset - the offset from which value has to be copied.

length - number of bytes to be copied from the value buffer.

writeType - write type to be used, one of BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT, BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE or BluetoothGattCharacteristic.WRITE_TYPE_SIGNED.

Returns:

The new request.

newReadRequest

@Deprecated
 @NonNull
public static ReadRequest newReadRequest(@Nullable
                                                                 android.bluetooth.BluetoothGattDescriptor descriptor)

Deprecated. Access to this method will change to package-only. Use BleManager.readDescriptor(BluetoothGattDescriptor) instead.

Creates new Read Descriptor request. The request will not be executed if given descriptor is null. After the operation is complete a proper callback will be invoked.

Parameters:

descriptor - descriptor to be read.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattDescriptor descriptor,
                                                                   @Nullable
                                                                   byte[] value)

Deprecated. Access to this method will change to package-only. Use BleManager.writeDescriptor(BluetoothGattDescriptor, byte[]) instead.

Creates new Write Descriptor request. The request will not be executed if given descriptor is null. After the operation is complete a proper callback will be invoked.

Parameters:

descriptor - descriptor to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

Returns:

The new request.

newWriteRequest

@Deprecated
 @NonNull
public static WriteRequest newWriteRequest(@Nullable
                                                                   android.bluetooth.BluetoothGattDescriptor descriptor,
                                                                   @Nullable
                                                                   byte[] value,
                                                                   int offset,
                                                                   int length)

Deprecated. Access to this method will change to package-only. Use BleManager.writeDescriptor(BluetoothGattDescriptor, byte[], int, int) instead.

Creates new Write Descriptor request. The request will not be executed if given descriptor is null. After the operation is complete a proper callback will be invoked.

Parameters:

descriptor - descriptor to be written.

value - value to be written. The array is copied into another buffer so it's safe to reuse the array again.

offset - the offset from which value has to be copied.

length - number of bytes to be copied from the value buffer.

Returns:

The new request.

newEnableNotificationsRequest

@Deprecated
 @NonNull
public static WriteRequest newEnableNotificationsRequest(@Nullable
                                                                                 android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.enableNotifications(BluetoothGattCharacteristic) instead.

Creates new Enable Notification request. The request will not be executed if given characteristic is null, does not have NOTIFY property or the CCCD. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to have notifications enabled.

Returns:

The new request.

newDisableNotificationsRequest

@Deprecated
 @NonNull
public static WriteRequest newDisableNotificationsRequest(@Nullable
                                                                                  android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.disableNotifications(BluetoothGattCharacteristic) instead.

Creates new Disable Notification request. The request will not be executed if given characteristic is null, does not have NOTIFY property or the CCCD. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to have notifications disabled.

Returns:

The new request.

newEnableIndicationsRequest

@Deprecated
 @NonNull
public static WriteRequest newEnableIndicationsRequest(@Nullable
                                                                               android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.enableIndications(BluetoothGattCharacteristic) instead.

Creates new Enable Indications request. The request will not be executed if given characteristic is null, does not have INDICATE property or the CCCD. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to have indications enabled.

Returns:

The new request.

newDisableIndicationsRequest

@Deprecated
 @NonNull
public static WriteRequest newDisableIndicationsRequest(@Nullable
                                                                                android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.disableNotifications(BluetoothGattCharacteristic) instead.

Creates new Disable Indications request. The request will not be executed if given characteristic is null, does not have INDICATE property or the CCCD. After the operation is complete a proper callback will be invoked.

Parameters:

characteristic - characteristic to have indications disabled.

Returns:

The new request.

newWaitForNotificationRequest

@Deprecated
 @NonNull
public static WaitForValueChangedRequest newWaitForNotificationRequest(@Nullable
                                                                                               android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.waitForNotification(BluetoothGattCharacteristic) instead.

Creates new Wait For Notification request. The request will not be executed if given characteristic is null, does not have NOTIFY property or the CCCD. After the operation is complete a proper callback will be invoked.

If the notification should be triggered by another operation (for example writing an op code), set it with WaitForValueChangedRequest.trigger(Operation).

Parameters:

characteristic - characteristic from which a notification should be received.

Returns:

The new request.

newWaitForIndicationRequest

@Deprecated
 @NonNull
public static WaitForValueChangedRequest newWaitForIndicationRequest(@Nullable
                                                                                             android.bluetooth.BluetoothGattCharacteristic characteristic)

Deprecated. Access to this method will change to package-only. Use BleManager.waitForIndication(BluetoothGattCharacteristic) instead.

Creates new Wait For Indication request. The request will not be executed if given characteristic is null, does not have INDICATE property or the CCCD. After the operation is complete a proper callback will be invoked.

If the indication should be triggered by another operation (for example writing an op code), set it with WaitForValueChangedRequest.trigger(Operation).

Parameters:

characteristic - characteristic from which a notification should be received.

Returns:

The new request.

newReadBatteryLevelRequest

@NonNull
 @Deprecated
public static ReadRequest newReadBatteryLevelRequest()

Deprecated. Use newReadRequest(BluetoothGattCharacteristic) with BatteryLevelDataCallback from Android BLE Common Library instead.

Creates new Read Battery Level request. The first found Battery Level characteristic value from the first found Battery Service. If any of them is not found, or the characteristic does not have the READ property this operation will not execute.

Returns:

The new request.

newEnableBatteryLevelNotificationsRequest

@NonNull
 @Deprecated
public static WriteRequest newEnableBatteryLevelNotificationsRequest()

Deprecated. Use newEnableNotificationsRequest(BluetoothGattCharacteristic) with BatteryLevelDataCallback from Android BLE Common Library instead.

Creates new Enable Notifications on the first found Battery Level characteristic from the first found Battery Service. If any of them is not found, or the characteristic does not have the NOTIFY property this operation will not execute.

Returns:

The new request.

newDisableBatteryLevelNotificationsRequest

@NonNull
 @Deprecated
public static WriteRequest newDisableBatteryLevelNotificationsRequest()

Deprecated. Use newDisableNotificationsRequest(BluetoothGattCharacteristic) instead.

Creates new Disable Notifications on the first found Battery Level characteristic from the first found Battery Service. If any of them is not found, or the characteristic does not have the NOTIFY property this operation will not execute.

Returns:

The new request.

newMtuRequest

@Deprecated
 @NonNull
public static MtuRequest newMtuRequest(int mtu)

Deprecated. Access to this method will change to package-only. Use BleManager.requestMtu(int) instead.

Requests new MTU (Maximum Transfer Unit). This is only supported on Android Lollipop or newer. On older platforms the request will enqueue, but will fail to execute and fail(FailCallback) callback will be called. The target device may reject requested value and set a smaller MTU.

Parameters:

mtu - the new MTU. Acceptable values are <23, 517>.

Returns:

The new request.

newConnectionPriorityRequest

@Deprecated
 @NonNull
public static ConnectionPriorityRequest newConnectionPriorityRequest(int priority)

Deprecated. Access to this method will change to package-only. Use BleManager.requestConnectionPriority(int) instead.

Requests the new connection priority. Acceptable values are:

1. ConnectionPriorityRequest.CONNECTION_PRIORITY_HIGH - Interval: 11.25 -15 ms (Android 6+) and 7.5 - 10 ms (older), latency: 0, supervision timeout: 20 sec,
2. ConnectionPriorityRequest.CONNECTION_PRIORITY_BALANCED - Interval: 30 - 50 ms, latency: 0, supervision timeout: 20 sec,
3. ConnectionPriorityRequest.CONNECTION_PRIORITY_LOW_POWER - Interval: 100 - 125 ms, latency: 2, supervision timeout: 20 sec.

Requesting connection priority is available on Android Lollipop or newer. On older platforms the request will enqueue, but will fail to execute and fail(FailCallback) callback will be called.

Parameters:

priority - one of: ConnectionPriorityRequest.CONNECTION_PRIORITY_HIGH, ConnectionPriorityRequest.CONNECTION_PRIORITY_BALANCED, ConnectionPriorityRequest.CONNECTION_PRIORITY_LOW_POWER.

Returns:

The new request.

newSetPreferredPhyRequest

@Deprecated
 @NonNull
public static PhyRequest newSetPreferredPhyRequest(int txPhy,
                                                                           int rxPhy,
                                                                           int phyOptions)

Deprecated. Access to this method will change to package-only. Use BleManager.setPreferredPhy(int, int, int) instead.

Requests the change of preferred PHY for this connections.

PHY LE 2M and PHY LE Coded are supported only on Android Oreo or newer. You may safely request other PHYs on older platforms, but the request will not be executed and you will get PHY LE 1M as TX and RX PHY in the callback.

Parameters:

txPhy - preferred transmitter PHY. Bitwise OR of any of PhyRequest.PHY_LE_1M_MASK, PhyRequest.PHY_LE_2M_MASK, and PhyRequest.PHY_LE_CODED_MASK.

rxPhy - preferred receiver PHY. Bitwise OR of any of PhyRequest.PHY_LE_1M_MASK, PhyRequest.PHY_LE_2M_MASK, and PhyRequest.PHY_LE_CODED_MASK.

phyOptions - preferred coding to use when transmitting on the LE Coded PHY. Can be one of PhyRequest.PHY_OPTION_NO_PREFERRED, PhyRequest.PHY_OPTION_S2 or PhyRequest.PHY_OPTION_S8.

Returns:

The new request.

newReadPhyRequest

@Deprecated
 @NonNull
public static PhyRequest newReadPhyRequest()

Deprecated. Access to this method will change to package-only. Use BleManager.readPhy() instead.

Reads the current PHY for this connections.

PHY LE 2M and PHY LE Coded are supported only on Android Oreo or newer. You may safely read PHY on older platforms, but the request will not be executed and you will get PHY LE 1M as TX and RX PHY in the callback.

Returns:

The new request.

newReadRssiRequest

@Deprecated
 @NonNull
public static ReadRssiRequest newReadRssiRequest()

Deprecated. Access to this method will change to package-only. Use BleManager.readRssi() instead.

Reads the current RSSI (Received Signal Strength Indication).

Returns:

The new request.

newRefreshCacheRequest

@Deprecated
 @NonNull
public static SimpleRequest newRefreshCacheRequest()

Deprecated. Access to this method will change to package-only. Use BleManager.refreshDeviceCache() instead.

Refreshes the device cache. As the BluetoothGatt#refresh() method is not in the public API (it's hidden, and on Android P it is on a light gray list) it is called using reflections and may be removed in some future Android release or on some devices.

There is no callback indicating when the cache has been cleared. This library assumes some time and waits. After the delay, it will start service discovery and clear the task queue. When the service discovery finishes, the BleManagerHandler.isRequiredServiceSupported(BluetoothGatt) and BleManagerHandler.isOptionalServiceSupported(BluetoothGatt) will be called and the initialization will be performed as if the device has just connected.

Returns:

The new request.

newSleepRequest

@Deprecated
 @NonNull
public static SleepRequest newSleepRequest(long delay)

Deprecated. Access to this method will change to package-only. Use BleManager.sleep(long) instead.

Creates new Sleep request that will postpone next request for given number of milliseconds.

Parameters:

delay - the delay in milliseconds.

Returns:

The new request.

done

@NonNull
public Request done(@NonNull
                              SuccessCallback callback)

Use to set a completion callback. The callback will be invoked when the operation has finished successfully unless the request was executed synchronously, in which case this callback will be ignored.

Parameters:

callback - the callback.

Returns:

The request.

fail

@NonNull
public Request fail(@NonNull
                              FailCallback callback)

Use to set a callback that will be called in case the request has failed. If the target device wasn't set before executing this request (BleManager.connect(BluetoothDevice) was never called), the invalid(InvalidRequestCallback) will be used instead, as the BluetoothDevice is not known.

This callback will be ignored if request was executed synchronously, in which case the error will be returned as an exception.

Parameters:

callback - the callback.

Returns:

The request.

invalid

@NonNull
public Request invalid(@NonNull
                                 InvalidRequestCallback callback)

Use to set a callback that will be called in case the request was invalid, for example called before the device was connected. This callback will be ignored if request was executed synchronously, in which case the error will be returned as an exception.

Parameters:

callback - the callback.

Returns:

The request.

before

@NonNull
public Request before(@NonNull
                                BeforeCallback callback)

Sets a callback that will be executed before the execution of this operation starts.

Parameters:

callback - the callback.

Returns:

The request.

enqueue

public void enqueue()

Enqueues the request for asynchronous execution.