Designing and Implementing a Workflow Approval System with Activiti

Workflow approval is a core capability of office OA systems; designing such a system requires careful handling of multiple users, task routing, and branch conditions. Without a powerful workflow engine, extending or adding new processes becomes cumbersome.

Using the open‑source Activiti engine simplifies these challenges: adding a new process only requires drawing a BPMN diagram and integrating a front‑end page.

Basic Steps

Draw a process diagram.

Test the diagram.

Configure the Activiti project.

Design the workflow engine database.

Introduce the workflow engine APIs.

Understand BPMN diagrams.

Compare similar workflow engines.

Explore further learning directions.

Summarize.

To implement a leave‑approval system, first create a BPMN diagram (e.g., apply.bpmn ) that defines a two‑level supervisor approval flow.

Deploying the Process Diagram

// Create the process engine
ProcessEngine engine = ProcessEngines.getDefaultProcessEngine();
// RepositoryService for deployment
RepositoryService repositoryService = engine.getRepositoryService();
// Deploy the leave‑process diagram
repositoryService.createDeployment().addClasspathResource("processes/apply.bpmn").deploy();

The deployment typically runs in the backend; no code changes are needed after the diagram is uploaded.

Starting a New Process Instance

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

The variables set the applicant and the two supervisors. The process key apply_processor_1 is defined in the BPMN file.

Completing the Applicant's Task

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

This step records the leave days (e.g., 4 days) and moves the flow to the supervisor approval node.

First‑Level Supervisor Approval

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

The variable result1 determines which exclusive‑gateway branch is taken.

Second‑Level Supervisor Approval (if needed)

Task thirdTask = taskService.createTaskQuery().taskAssignee("wang5").singleResult();
if (thirdTask != null) {
    taskService.setVariable(thirdTask.getId(), "result2", true);
    taskService.complete(thirdTask.getId());
} else {
    // No second‑level approval required
}

The exclusive gateway uses the condition #{day>3} to decide whether this step is executed.

Viewing the Execution History

List
activityInstanceList = historyService
    .createHistoricActivityInstanceQuery()
    .processInstanceId(instance.getId())
    .list();
for (HistoricActivityInstance historicActivityInstance : activityInstanceList) {
    log.warn("activityName:{}, activityType:{}, assignee:{}, taskId:{}",
        historicActivityInstance.getActivityName(),
        historicActivityInstance.getActivityType(),
        historicActivityInstance.getAssignee(),
        historicActivityInstance.getTaskId());
}

This logs each executed node, allowing full traceability of the workflow.

Project Basic Configuration

Add the Activiti starter dependency:

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

Use Spring Boot parent 2.5.4 and configure a datasource (H2 for learning or MySQL for production). Example XML configuration creates the datasource and the StandaloneProcessEngineConfiguration bean.

Database Schema

Activiti creates several tables:

ACT_RE_* – process definitions and resources.

ACT_RU_* – runtime data such as tasks, process instances, and variables.

ACT_HI_* – historic data for audit and analysis.

ACT_ID_* – user, group, and permission information.

Other auxiliary tables for events, jobs, and timers.

Workflow Engine API Overview

ProcessEngine : entry point to obtain service APIs.

RepositoryService : deploy and manage process definitions.

RuntimeService : start, suspend, or delete process instances.

TaskService : query, claim, and complete tasks.

HistoryService : query completed tasks and historic process data.

What is BPMN?

BPMN (Business Process Model and Notation) is a standard for modeling business processes. Activiti implements BPMN 2.0, allowing designers to create XML‑based process definitions that the engine can execute.

Further Learning Directions

Event types and listeners.

Different task types (user, service, script).

Form management.

Parallel and exclusive gateways.

Performance, scaling, and sharding strategies.

Summary

Activiti is suitable for multi‑user process management.

Workflow development consists of diagram design, deployment, and instance execution.

Adding new process templates requires no additional code; only front‑end pages and simple back‑end interfaces need to be adapted.