How to get tasks from process instance id using camundatasklistclient api in java camunda 8

Question

I am using camunda 8 and refering below link for getting task from processinstance id https://github.com/camunda-community-hub/camunda-tasklist-client-java

I have added the dependency mentioned in link. My simpleauthentication is also done. Camundatasklistclient object is also initialised. But when running below step it shows error : impleAuthentication sa = new SimpleAuthentication("demo", "demo");

//shouldReturnVariables will change the default behaviour for the client to query variables along with tasks.

CamundaTaskListClient client = new CamundaTaskListClient.Builder().taskListUrl("http://localhost:8081").shouldReturnVariables().authentication(sa).build();
//get tasks from a process instance (TaskSearch can take many more parameters)
TaskSearch ts = new TaskSearch().setProcessInstanceId("2251799818839086");
TaskList tasksFromInstance = client.getTasks(ts); // this statement gives error at runtime 

Error : io.camunda.tasklist.exception.TaskListException:Error(message=Validation error of type wrongtype argument query with value 'ObjectValue{objectfields{objectfields=candidategroup, assignee, assigned,state,processDefinitionId,processInstanceId,pagesize,search after,search before,contains a filed not in Taskquery : processDefinitionId @ tasks

How to resolve this error ?

Answer 1

Have you checked if the versions of the client library and the servers side API match? It looks like the client lib is including processDefinitionId, but the the Taskquery API does not contain it.

Version 8.1 an 8.2 contains processDefinitionId:

input TaskQuery {
  state: TaskState
  assigned: Boolean
  assignee: String
  candidateGroup: String
  candidateUser: String
  processDefinitionId: String
  processInstanceId: String
  followUpDate: DateFilter
  dueDate: DateFilter
  pageSize: Int
  taskDefinitionId: String
  searchAfter: [String!]
  searchAfterOrEqual: [String!]
  searchBefore: [String!]
  searchBeforeOrEqual: [String!]
  sort: [TaskOrderBy]
}

https://docs.camunda.io/docs/apis-tools/tasklist-api/inputs/task-query/

Version 8.0 does not contain it:

type TaskQuery {
  state: TaskState
  assigned: Boolean
  assignee: String
  candidateGroup: String
  pageSize: Int
  taskDefinitionId: String
  searchAfter: [String!]
  searchAfterOrEqual: [String!]
  searchBefore: [String!]
  searchBeforeOrEqual: [String!]
}

https://docs.camunda.io/docs/8.0/apis-tools/tasklist-api/inputs/task-query/

=> Upgrade your server side and try again

Answer 2

The Camunda 8 Tasklist client API seems to be encountering issues without a viable resolution from the Camunda team. In lieu of a functional fix, the suggested approach is to manually obtain a token using HTTP, followed by retrieving a session ID, and consequently employing the REST API for desired operations. This alternate method involves obtaining authentication through token-based processes and utilizing the REST API to facilitate the required functionalities.