Designing and Implementing an OA Approval Workflow with Activiti: From BPMN Modeling to Spring Boot Integration

The workflow approval feature is a core capability of office OA systems, requiring careful design to handle multiple users, task transitions, and branch decisions.

Activiti Workflow Engine Overview

Activiti provides a powerful engine to model, deploy, and execute BPMN 2.0 processes, eliminating the need for custom code to drive flow control and branching.

Key Steps to Build a Workflow

Draw the BPMN diagram using the actiBPM plugin in IDEA.

Deploy the diagram to the engine.

Start a process instance with required variables.

Query and complete tasks for each approver.

Use exclusive gateways to decide branch paths based on variables such as ${day} or approval results.

Code Example: Deploying the Process

ProcessEngine engine = ProcessEngines.getDefaultProcessEngine();
RepositoryService repositoryService = engine.getRepositoryService();
repositoryService.createDeployment()
    .addClasspathResource("processes/apply.bpmn")
    .deploy();

This deployment creates the process definition in the ACT_RE_* tables.

Starting a Process Instance

Map
vars = new HashMap<>();
vars.put("applyUser", "zhang3");
vars.put("supervisor", "li4");
vars.put("upperSupervisor", "wang5");
ProcessInstance instance = runtimeService.startProcessInstanceByKey("apply_processor_1", vars);

The instance ID can be used later to query history.

Task Handling for Approvers

Task firstTask = taskService.createTaskQuery().taskAssignee("zhang3").singleResult();
taskService.complete(firstTask.getId(), Maps.newHashMap("day", 4));

Task secondTask = taskService.createTaskQuery().taskAssignee("li4").singleResult();
taskService.setVariable(secondTask.getId(), "result1", true);
taskService.complete(secondTask.getId());

Task thirdTask = taskService.createTaskQuery().taskAssignee("wang5").singleResult();
if (thirdTask != null) {
    taskService.setVariable(thirdTask.getId(), "result2", true);
    taskService.complete(thirdTask.getId());
}

Variables set by each approver are evaluated by exclusive gateways to determine the next path.

Database Tables Used by Activiti

ACT_RE_* : Process definitions and resources.

ACT_RU_* : Runtime data such as tasks and executions.

ACT_HI_* : Historical activity records.

ACT_ID_* : Identity and permission data.

API Overview

ProcessEngine : Entry point to obtain services.

RepositoryService : Deploy and manage process definitions.

RuntimeService : Start and control process instances.

TaskService : Query, claim, and complete user tasks.

HistoryService : Retrieve historic activity and variable data.

Comparison with Camunda and Flowable

Both Camunda and Flowable are forks of Activiti and share a similar development workflow, but differ in community support, feature sets, and performance optimizations.

Further Learning Directions

Event types and listeners.

Different task types: user, service, script.

Form management and UI integration.

Parallel gateways and complex routing.

Scalability concerns: ID generation, sharding.

Conclusion

Activiti simplifies multi‑user approval processes by handling flow control and branching through BPMN models, requiring only minimal Java code for deployment, instance creation, and task completion, while front‑end pages handle user interaction.