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

Method Summary

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) Defines fetching of external tasks by using a fluent builder.
void	handleFailure(String externalTaskId, String workerId, String errorMessage, int retries, long retryTimeout) Signals that an external task could not be successfully executed.
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)

Defines fetching of external tasks by using a fluent builder. A worker id and a maximum number of tasks to fetch must be specified. The builder allows to specify multiple topics to fetch tasks for and individual lock durations. For every topic, variables can be fetched in addition.

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

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 - the 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

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

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.