Building a Multi‑Level Approval Workflow with Activiti in Java

The core of an office OA system is the workflow approval feature; designing a robust multi‑level approval process can be simplified with the Activiti open‑source workflow engine.

Step 1 – Draw the BPMN diagram : Use the actiBPM plugin in IntelliJ to create a diagram (apply.bpmn) that defines a first‑level supervisor approval and, if the leave exceeds three days, a second‑level supervisor approval.

Step 2 – Deploy the diagram :

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

The deployment code is usually placed in the backend service; no further code changes are needed after the diagram is uploaded.

Step 3 – Start a process instance by providing the applicant and supervisors:

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

Step 4 – Complete the applicant's task and set the requested leave days:

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

Step 5 – First‑level supervisor approval (sets result1 variable):

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

Step 6 – Conditional second‑level approval (executed only when day > 3 ):

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

The exclusive gateways in the BPMN file use expressions such as #{result1==true} and #{day>3} to decide which path to follow, eliminating the need for custom branching code.

Database tables created by Activiti :

Definition tables: ACT_RE_*

Runtime tables: ACT_RU_*

History tables: ACT_HI_*

Identity tables: ACT_ID_*

Key services (API) :

ProcessEngine – entry point to obtain other services.

RepositoryService – deploy and delete process definitions.

RuntimeService – start, suspend, or delete process instances.

TaskService – query, claim, and complete tasks.

HistoryService – query completed tasks and historic variables.

Project setup (Spring Boot 2.5.4, Activiti 5.23.0):

<dependency>
    <groupId>org.activiti</groupId>
    <artifactId>activiti-spring-boot-starter-basic</artifactId>
    <version>5.23.0</version>
</dependency>

Configure a datasource (H2 for quick testing) and the engine configuration bean as shown in the original XML snippet.

Extending the flow : To add HR approval for sick leave, insert an exclusive gateway before the final approval node and create a new user task with assignee ${hr} , using the same pattern of variables and gateways—no additional Java code is required.

Comparison with other BPM engines (Camunda, Flowable) shows similar five‑step usage: design BPMN, deploy, start instance, execute tasks, and monitor.

Learning roadmap includes event listeners, task types, form management, parallel gateways, performance tuning, and database sharding.

Summary : Activiti enables multi‑user workflow management with minimal code; the heavy lifting of task routing and state persistence is handled by the engine, leaving developers to focus on UI and simple service interfaces.