Camunda : get active tasks

How can i get a list of active tasks in the code i use in Camunda ?

I already look at this answer "How to query the position of a process instance?" but i can't understand what is "processInstanceId" and where i am supposed to get it to make this method works.

Here's the code i'm currently trying :

package org.camunda.bpm;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.camunda.bpm.engine.ProcessEngine;
import org.camunda.bpm.engine.RepositoryService;
import org.camunda.bpm.engine.RuntimeService;
import org.camunda.bpm.engine.runtime.ProcessInstance;
import org.camunda.bpm.model.bpmn.BpmnModelInstance;
import org.camunda.bpm.model.xml.instance.ModelElementInstance;

public class AllActiveActivities {

public Map<String, String> getAllActiveActivities(String processInstanceId) {
// get engine services
ProcessEngine processEngine = BpmPlatform.getDefaultProcessEngine()
RuntimeService runtimeService = processEngine.getRuntimeService();
RepositoryService repositoryService = processEngine.getRepositoryService();

// get the process instance
ProcessInstance processInstance =
    runtimeService.createProcessInstanceQuery()
        .processInstanceId(processInstanceId)
        .singleResult();

HashMap<String, String> activityNameByActivityId = new HashMap<String, String>();

// get all active activities of the process instance
List<String> activeActivityIds =
    runtimeService.getActiveActivityIds(processInstance.getId());

// get bpmn model of the process instance
BpmnModelInstance bpmnModelInstance =
    repositoryService.getBpmnModelInstance(processInstance.getProcessDefinitionId());

for (String activeActivityId : activeActivityIds) {
  // get the speaking name of each activity in the diagram
  ModelElementInstance modelElementById =
      bpmnModelInstance.getModelElementById(activeActivityId);
  String activityName = modelElementById.getAttributeValue("name");

  activityNameByActivityId.put(activeActivityId, activityName);
}

// map contains now all active activities
return activityNameByActivityId;
}

}

Thanks in advance for your help.

The following statement will return all active tasks, which can be also standalone tasks.

processEngine.getTaskService().createTaskQuery().active().list()

If you want to get all active tasks corresponding to a specific running process you have to add the .processInstanceId(processInstanceId) to the statement before the .list(). The processInstanceId is the id which identifies the process instance. If you start a process/workflow a process instance will be created with an unique id. To get these id you can for example execute the following statement.

int processInstanceId = processEngine.getRuntimeService()
 .createProcessInstanceQuery()
 .processDefinitionKey(processDefinitionKey)
 .singleResult()
 .getId()

The variable processDefinitionKey is the id which is set in the process definition xml.