org.camunda.bpm.engine

Interface ExternalTaskService

All Known Implementing Classes:

ExternalTaskServiceImpl

public interface ExternalTaskService

Service that provides access to ExternalTask instances. External tasks represent work items that are processed externally and independently of the process engine.

Author:

Thorben Lindhauer, Christopher Zell

Method Summary

Methods

Modifier and Type	Method and Description
void	complete(String externalTaskId, String workerId) Completes an external task on behalf of a worker.
void	complete(String externalTaskId, String workerId, Map<String,Object> variables) Completes an external task on behalf of a worker and submits variables to the process instance before continuing execution.
ExternalTaskQuery	createExternalTaskQuery() Queries for tasks that the currently authenticated user has at least one of the following permissions for: Permissions.READ on Resources.PROCESS_INSTANCE Permissions.READ_INSTANCE on Resources.PROCESS_DEFINITION
ExternalTaskQueryBuilder	fetchAndLock(int maxTasks, String workerId) Calls method fetchAndLock(maxTasks, workerId, usePriority), where usePriority is false.
ExternalTaskQueryBuilder	fetchAndLock(int maxTasks, String workerId, boolean usePriority) Defines fetching of external tasks by using a fluent builder.
String	getExternalTaskErrorDetails(String externalTaskId) Returns the full error details that occurred while running external task with the given id.
void	handleBpmnError(String externalTaskId, String workerId, String errorCode) Signals that an business error appears, which should be handled by the process engine.
void	handleFailure(String externalTaskId, String workerId, String errorMessage, int retries, long retryTimeout) Signals that an external task could not be successfully executed.
void	handleFailure(String externalTaskId, String workerId, String errorMessage, String errorDetails, int retries, long retryTimeout) Signals that an external task could not be successfully executed.
void	setPriority(String externalTaskId, long priority) Sets the priority for an external task.
void	setRetries(String externalTaskId, int retries) Sets the retries for an external task.
void	unlock(String externalTaskId) Unlocks an external task instance.

Method Detail

fetchAndLock

ExternalTaskQueryBuilder fetchAndLock(int maxTasks,
                                    String workerId)

Calls method fetchAndLock(maxTasks, workerId, usePriority), where usePriority is false.

Parameters:

maxTasks - the maximum number of tasks to return

workerId - the id of the worker to lock the tasks for

Returns:

a builder to define and execute an external task fetching operation

See Also:

ExternalTaskService#fetchAndLock(int, java.lang.String, boolean)}.

fetchAndLock

ExternalTaskQueryBuilder fetchAndLock(int maxTasks,
                                    String workerId,
                                    boolean usePriority)

Defines fetching of external tasks by using a fluent builder. The following parameters must be specified: A worker id, a maximum number of tasks to fetch and a flag that indicates whether priority should be regarded or not. The builder allows to specify multiple topics to fetch tasks for and individual lock durations. For every topic, variables can be fetched in addition.Is the priority enabled the tasks with the highest priority are fetched.

Returned tasks are locked for the given worker until now + lockDuration expires. Locked tasks cannot be fetched or completed by other workers. When the lock time has expired, a task may be fetched and locked by other workers.

Returns at most maxTasks tasks. The tasks are arbitrarily distributed among the specified topics. Example: Fetching 10 tasks of topics "a"/"b"/"c" may return 3/3/4 tasks, or 10/0/0 tasks, etc.

May return less than maxTasks tasks, if there exist not enough unlocked tasks matching the provided topics or if parallel fetching by other workers results in locking failures.

Returns only tasks that the currently authenticated user has at least one permission out of all of the following groups for:

• Permissions.READ on Resources.PROCESS_INSTANCE
• Permissions.READ_INSTANCE on Resources.PROCESS_DEFINITION

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

Parameters:

maxTasks - the maximum number of tasks to return

workerId - the id of the worker to lock the tasks for

usePriority - the flag to enable the priority fetching mechanism

Returns:

a builder to define and execute an external task fetching operation

complete

void complete(String externalTaskId,
            String workerId)

Completes an external task on behalf of a worker. The given task must be assigned to the worker.

Parameters:

externalTaskId - the id of the external to complete

workerId - the id of the worker that completes the task

Throws:

NotFoundException - if no external task with the given id exists

BadUserRequestException - if the task is assigned to a different worker

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

complete

void complete(String externalTaskId,
            String workerId,
            Map<String,Object> variables)

Completes an external task on behalf of a worker and submits variables to the process instance before continuing execution. The given task must be assigned to the worker.

Parameters:

externalTaskId - the id of the external to complete

workerId - the id of the worker that completes the task

variables - a map of variables to set on the execution (non-local) the external task is assigned to

Throws:

NotFoundException - if no external task with the given id exists

BadUserRequestException - if the task is assigned to a different worker

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

handleFailure

void handleFailure(String externalTaskId,
                 String workerId,
                 String errorMessage,
                 int retries,
                 long retryTimeout)

Signals that an external task could not be successfully executed. The task must be assigned to the given worker. The number of retries left can be specified. In addition, a timeout can be provided, such that the task cannot be fetched before now + retryTimeout again.

If retries is 0, an incident with the given error message is created. The incident gets resolved, once the number of retries is increased again.

Parameters:

externalTaskId - the id of the external task to report a failure for

workerId - the id of the worker that reports the failure

errorMessage - short error message related to this failure. This message can be retrieved via ExternalTask.getErrorMessage() and is used as the incident message in case retries is null. May be null.

retries - the number of retries left. External tasks with 0 retries cannot be fetched anymore unless the number of retries is increased via API. Must be >= 0.

retryTimeout - the timeout before the task can be fetched again. Must be >= 0.

Throws:

NotFoundException - if no external task with the given id exists

BadUserRequestException - if the task is assigned to a different worker

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

handleFailure

void handleFailure(String externalTaskId,
                 String workerId,
                 String errorMessage,
                 String errorDetails,
                 int retries,
                 long retryTimeout)

Signals that an external task could not be successfully executed. The task must be assigned to the given worker. The number of retries left can be specified. In addition, a timeout can be provided, such that the task cannot be fetched before now + retryTimeout again.

If retries is 0, an incident with the given error message is created. The incident gets resolved, once the number of retries is increased again.

Parameters:

externalTaskId - the id of the external task to report a failure for

workerId - the id of the worker that reports the failure

errorMessage - short error message related to this failure. This message can be retrieved via ExternalTask.getErrorMessage() and is used as the incident message in case retries is null. May be null.

errorDetails - full error message related to this failure. This message can be retrieved via getExternalTaskErrorDetails(String) ()}

retries - the number of retries left. External tasks with 0 retries cannot be fetched anymore unless the number of retries is increased via API. Must be >= 0.

retryTimeout - the timeout before the task can be fetched again. Must be >= 0.

Throws:

NotFoundException - if no external task with the given id exists

BadUserRequestException - if the task is assigned to a different worker

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

handleBpmnError

void handleBpmnError(String externalTaskId,
                   String workerId,
                   String errorCode)

Signals that an business error appears, which should be handled by the process engine. The task must be assigned to the given worker. The error will be propagated to the next error handler. Is no existing error handler for the given bpmn error the activity instance of the external task ends.

Parameters:

externalTaskId - the id of the external task to report a bpmn error

workerId - the id of the worker that reports the bpmn error

errorCode - the error code of the corresponding bmpn error

Throws:

NotFoundException - if no external task with the given id exists

BadUserRequestException - if the task is assigned to a different worker

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

Since:

7.5

unlock

void unlock(String externalTaskId)

Unlocks an external task instance.

Parameters:

externalTaskId - the id of the task to unlock

Throws:

NotFoundException - if no external task with the given id exists

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

setRetries

void setRetries(String externalTaskId,
              int retries)

Sets the retries for an external task. If the new value is 0, a new incident with a null message is created. If the old value is 0 and the new value is greater than 0, an existing incident is resolved.

Parameters:

externalTaskId - the id of the task to set the

retries -

Throws:

NotFoundException - if no external task with the given id exists

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

setPriority

void setPriority(String externalTaskId,
               long priority)

Sets the priority for an external task.

Parameters:

externalTaskId - the id of the task to set the

priority - the new priority of the task

Throws:

NotFoundException - if no external task with the given id exists

AuthorizationException - thrown if the current user does not possess any of the following permissions:

• Permissions.UPDATE on Resources.PROCESS_INSTANCE
• Permissions.UPDATE_INSTANCE on Resources.PROCESS_DEFINITION

createExternalTaskQuery

ExternalTaskQuery createExternalTaskQuery()

Queries for tasks that the currently authenticated user has at least one of the following permissions for:

• Permissions.READ on Resources.PROCESS_INSTANCE
• Permissions.READ_INSTANCE on Resources.PROCESS_DEFINITION

Returns:

a new ExternalTaskQuery that can be used to dynamically query for external tasks.

getExternalTaskErrorDetails

String getExternalTaskErrorDetails(String externalTaskId)

Returns the full error details that occurred while running external task with the given id. Returns null when the external task has no error details.

Parameters:

externalTaskId - id of the external task, cannot be null.

Throws:

ProcessEngineException - When no external task exists with the given id.

AuthorizationException - If the user has no Permissions.READ permission on Resources.PROCESS_INSTANCE or no Permissions.READ_INSTANCE permission on Resources.PROCESS_DEFINITION.

Since:

7.6